JP2018125625A - Atomic oscillators, electronic equipment and mobile objects - Google Patents

Abstract

To provide an atomic oscillator capable of improving the oscillation characteristics while reducing the cost, and to provide an electronic device and a moving body including such an atomic oscillator. An atomic cell in which an alkali metal is sealed, a light source unit that emits light to irradiate the alkali metal, and the light transmitted through the atomic cell are received and a signal corresponding to the received light intensity is output. A light receiving portion that is disposed between the light source portion and the atomic cell, and the lens diverges or focuses the light toward the atomic cell and emits the light. An atomic oscillator. [Selection] Figure 5

Description

  The present invention relates to an atomic oscillator, an electronic device, and a moving object.

  As an oscillator having high long-term frequency stability, an atomic oscillator that oscillates based on energy transition of alkali metal atoms such as rubidium and cesium is known (for example, see Patent Document 1).

  As such an atomic oscillator, Patent Document 1 discloses an atomic clock including a vertical cavity surface emitting laser (light source unit), a quarter wavelength plate, a gas phase cell (atomic cell), and a detector (light receiving unit). Has been. Here, the quarter-wave plate, the gas phase cell, and the detector are respectively disposed inclined with respect to the emission surface of the vertical cavity surface emitting laser. This reduces the light from the vertical cavity surface emitting laser from being reflected by the quarter wave plate, the gas phase cell and the detector and returning to the vertical cavity surface emitting laser.

JP 2011-237401 A

  However, the atomic clock described in Patent Document 1 has a problem that it is difficult to assemble the quarter-wave plate, the gas phase cell, and the detector as described above, and as a result, the cost increases.

  An object of the present invention is to provide an atomic oscillator capable of improving the oscillation characteristics while reducing the cost, and to provide an electronic apparatus and a moving body including such an atomic oscillator.

The above object is achieved by the present invention described below.
The atomic oscillator of the present invention includes an atomic cell in which an alkali metal is enclosed,
A light source unit that emits light to irradiate the alkali metal;
A light receiving unit that receives the light transmitted through the atomic cell and outputs a signal corresponding to the received light intensity;
A lens disposed between the light source unit and the atomic cell,
The lens is characterized in that the light diverges or converges toward the atomic cell and is emitted.

  According to such an atomic oscillator, since the lens disposed between the light source unit and the atomic cell emits the light from the light source unit that diverges or converges toward the atomic cell, the light is emitted from the atomic cell, Even if the light is reflected by the light receiving part or the like, the reflected light can be condensed at a position different from that of the light source part (particularly, the part that emits light). Therefore, the amount of the reflected light incident on the light source unit as the return light can be reduced, and the output fluctuation (wavelength fluctuation, intensity fluctuation) of the light source part due to the return light can be reduced. As a result, the frequency characteristics of the atomic oscillator can be improved. Further, since it is not necessary to dispose the atomic cell, the light receiving unit and the lens as in the case of Patent Document 1, the assembly thereof is easy, and as a result, the cost of the atomic oscillator can be reduced.

The atomic oscillator of the present invention includes an atomic cell in which an alkali metal is enclosed,
A light source unit that emits light to irradiate the alkali metal;
A light receiving unit that receives the light transmitted through the atomic cell and outputs a signal corresponding to the received light intensity;
A lens disposed between the light source unit and the atomic cell,
The focal point of the lens is shifted in the optical axis direction with respect to a portion of the light source that emits the light.

  According to such an atomic oscillator, the lens arranged between the light source unit and the atomic cell has a focal point at a position shifted in the optical axis direction with respect to the light emitting part of the light source unit. Even if the light is reflected by the atomic cell, the light receiving part, etc., the reflected light can be condensed at a position different from that of the light source part (particularly, the part that emits light). Therefore, the amount of the reflected light incident on the light source unit as the return light can be reduced, and the output fluctuation (wavelength fluctuation, intensity fluctuation) of the light source part due to the return light can be reduced. As a result, the frequency characteristics of the atomic oscillator can be improved. Further, since it is not necessary to dispose the atomic cell, the light receiving unit and the lens as in the case of Patent Document 1, the assembly thereof is easy, and as a result, the cost of the atomic oscillator can be reduced.

The atomic oscillator of the present invention preferably includes a neutral density filter disposed between the light source unit and the lens.
Thereby, the intensity | strength of the light irradiated to an alkali metal can be optimized easily. Further, since the return light also passes through the neutral density filter, the amount of return light to the light source unit can be further reduced.

In the atomic oscillator of the present invention, it is preferable that the neutral density filter contains a substance that absorbs the light.
Thereby, it can reduce that the light from a light source part is reflected by a neutral density filter, and becomes return light.

In the atomic oscillator according to the aspect of the invention, it is preferable that the atomic oscillator includes a reflection reduction layer that is disposed on the neutral density filter and reduces reflection of the light.
Thereby, it can reduce that the light from a light source part reflects on the surface of a neutral density filter, and becomes return light.

In the atomic oscillator according to the aspect of the invention, it is preferable that the lens diverges the light toward the atomic cell.
Thereby, compared with the case where a lens focuses light toward an atomic cell, the amount of return light to the light source unit can be easily reduced.

The atomic oscillator of the present invention includes a package that houses the light source unit,
The package preferably has a window portion through which the light is transmitted.
As a result, the temperature of the light source unit can be adjusted independently of the atomic cell, and as a result, the output fluctuation due to the temperature fluctuation of the light source unit can be easily reduced.

In the atomic oscillator according to the aspect of the invention, it is preferable that the atomic oscillator includes a reflection reduction layer that is disposed on a surface of the window portion on the light source unit side and reduces reflection of the light.
Thereby, it can reduce that the light from a light source part reflects in a window part, and becomes return light. Here, since the window portion of the package housing the light source portion is located very close to the light source portion, light from the light source portion is likely to enter the light source portion as return light when reflected by the window portion. Therefore, reducing the reflected light at the window is particularly effective in reducing the amount of return light to the light source.

In the atomic oscillator of the present invention, the window portion is preferably a neutral density filter.
Thereby, it can reduce that the light from a light source part is reflected by a neutral density filter, and becomes return light. Further, a neutral density filter provided outside the package can be omitted, and the configuration of the atomic oscillator can be simplified.

An electronic apparatus according to the present invention includes the atomic oscillator according to the present invention.
According to such an electronic device, the effect (for example, excellent frequency characteristics) of the atomic oscillator can be enjoyed and excellent characteristics can be exhibited.

The moving body of the present invention includes the atomic oscillator of the present invention.
According to such a moving body, the effect (for example, excellent frequency characteristics) of the atomic oscillator can be enjoyed and excellent characteristics can be exhibited.

It is the schematic which shows the atomic oscillator which concerns on embodiment of this invention. It is sectional drawing of the atomic oscillator shown in FIG. It is sectional drawing of the light emitting element module with which the atomic oscillator shown in FIG. 2 is provided. It is a schematic diagram for demonstrating the optical path at the time of arrange | positioning the light source part on the focus of a condensing lens. It is a schematic diagram for demonstrating the optical path of the atomic oscillator (when a light source part is arrange | positioned in the position shifted | deviated from the focus of the condensing lens) shown in FIG. 6 is a graph showing the relationship between the distance (position) from the optical axis shown in FIGS. 4 and 5 and the intensity of return light (return light considering only light collection by a condensing lens). It is a graph showing the relationship between various conditions (A to M) when the transmittance of the neutral density filter is 2% and the intensity of the return light (condensation by the condensing lens and return light in consideration of reflection by other elements). is there. It is a graph showing the relationship between various conditions (A to M) when the transmittance of the neutral density filter is 10% and the intensity of the return light (condensation by the condenser lens and return light in consideration of reflection by other elements). is there. The graph which shows the relationship between the various conditions (A-M) in the case of the refractive index 1.51 of a condensing lens, and the intensity | strength of return light (condensation by a condensing lens, and reflection light in consideration of other elements) It is. FIG. 3 is a schematic diagram illustrating a modification of the atomic oscillator illustrated in FIG. 2. It is a figure which shows schematic structure at the time of using the atomic oscillator of this invention for the positioning system using a GPS satellite. It is a figure which shows an example of the moving body of this invention.

  Hereinafter, an atomic oscillator, an electronic apparatus, and a moving body of the present invention will be described in detail based on embodiments shown in the accompanying drawings.

1. Atomic Oscillator First, the atomic oscillator of the present invention will be described.

FIG. 1 is a schematic diagram showing an atomic oscillator according to an embodiment of the present invention.
The atomic oscillator 1 shown in FIG. 1 has a quantum phenomenon in which, when two resonant lights having specific different wavelengths are simultaneously irradiated to an alkali metal atom, the two resonant lights are transmitted without being absorbed by the alkali metal atom. It is an atomic oscillator that uses interference effects (CPT: Coherent Population Trapping). This phenomenon due to the quantum interference effect is also called an electromagnetically induced transparency (EIT) phenomenon.

  As shown in FIG. 1, the atomic oscillator 1 includes a light emitting element module 10, an atomic cell unit 20, an optical system unit 30 provided between the light emitting element module 10 and the atomic cell unit 20, and a light emitting element. And a control unit 50 that controls the operation of the module 10 and the atomic cell unit 20. Hereinafter, first, an outline of the atomic oscillator 1 will be described.

  The light emitting element module 10 includes a Peltier element 2, a light emitting element 3 (light source unit), and a temperature sensor 4. The light emitting element 3 emits linearly polarized light LL including two types of light having different frequencies. The temperature sensor 4 detects the temperature of the light emitting element 3. In addition, the Peltier element 2 adjusts the temperature of the light emitting element 3 (heating or cooling the light emitting element 3).

  The optical system unit 30 includes a neutral density filter 301, a condenser lens 302 (lens), and a quarter wavelength plate 303. The neutral density filter 301 reduces the intensity of the light LL from the light emitting element 3 described above. The condensing lens 302 adjusts the emission angle of the light LL (for example, the light LL is brought close to parallel light). The quarter-wave plate 303 converts the two types of light having different frequencies included in the light LL from linearly polarized light to circularly polarized light (right circularly polarized light or left circularly polarized light).

  The atomic cell unit 20 includes an atomic cell 201, a light receiving element 202 (light receiving unit), a heater 203, a temperature sensor 204, and a coil 205.

  The atomic cell 201 has light transparency, and an alkali metal is sealed in the atomic cell 201. The alkali metal atom has a three-level energy level composed of two different ground levels and excited levels. The light LL from the light emitting element 3 enters the atomic cell 201 via the neutral density filter 301, the condenser lens 302, and the quarter wavelength plate 303. The light receiving element 202 receives the light LL that has passed through the atomic cell 201 and outputs a signal corresponding to the received light intensity.

  The heater 203 heats the alkali metal in the atomic cell 201 to bring at least a part of the alkali metal into a gas state with a desired concentration. Further, the temperature sensor 204 detects the temperature of the atomic cell 201. The coil 205 applies a magnetic field in a predetermined direction to the alkali metal in the atomic cell 201 to cause Zeeman splitting of the energy level of the alkali metal atom. In such a state where the alkali metal atom is Zeeman split, when the circularly polarized resonant light pair as described above is irradiated to the alkali metal atom, the desired energy among the plurality of levels where the alkali metal atom is Zeeman split. The number of alkali metal atoms at the level can be made relatively larger than the number of alkali metal atoms at other energy levels. Therefore, the number of atoms that develop the desired EIT phenomenon increases, and the desired EIT signal (a signal that appears in the output signal of the light receiving element 202 with the EIT phenomenon) increases. As a result, the oscillation characteristics of the atomic oscillator 1 (particularly, (Short-term frequency stability) can be improved.

  The control unit 50 includes a temperature control unit 501, a light source control unit 502, a magnetic field control unit 503, and a temperature control unit 504. The temperature control unit 501 controls energization to the heater 203 based on the detection result of the temperature sensor 204 so that the inside of the atomic cell 201 becomes a desired temperature. The magnetic field control unit 503 controls energization to the coil 205 so that the magnetic field generated by the coil 205 is constant. Further, the temperature control unit 504 controls energization of the Peltier element 2 based on the detection result of the temperature sensor 4 so that the temperature of the light emitting element 3 becomes a desired temperature (in the temperature range).

  The light source control unit 502 controls the frequencies of the two types of light included in the light LL from the light emitting element 3 so that the EIT phenomenon occurs based on the detection result of the light receiving element 202. Here, when these two types of light become resonant light pairs having a frequency difference corresponding to the energy difference between the two ground levels of the alkali metal atoms in the atomic cell 201, the EIT phenomenon occurs. The light source control unit 502 includes a voltage-controlled crystal oscillator (not shown) whose oscillation frequency is controlled so as to be stabilized in synchronization with the above-described control of the two types of light frequencies. The output signal of the controlled crystal oscillator (VCXO) is output as the output signal (clock signal) of the atomic oscillator 1.

  The outline of the atomic oscillator 1 has been described above. Hereinafter, a more specific configuration of the atomic oscillator 1 will be described with reference to FIGS. 2 and 3.

  FIG. 2 is a cross-sectional view of the atomic oscillator shown in FIG. FIG. 3 is a cross-sectional view of a light emitting element module provided in the atomic oscillator shown in FIG. In the following, for convenience of explanation, the upper side in FIG. 2 is also referred to as “upper” and the lower side is also referred to as “lower”.

  As shown in FIG. 2, the atomic oscillator 1 includes a light emitting element module 10, an atomic cell unit 20, an optical system unit 30 that holds the light emitting element module 10, an atomic cell unit 20, and an optical system unit 30. And a control member 50 electrically connected to the light emitting element module 10 and the atomic cell unit 20, and a package 60 containing them.

(Light emitting element module)
As shown in FIG. 3, the light-emitting element module 10 includes a Peltier element 2, a light-emitting element 3, a temperature sensor 4, and a package 5 that houses them.

  The package 5 includes a base 51 having a recess 511 and a lid 52 that closes the opening of the recess 511. The Peltier element 2, the light emitting element 3, and the temperature sensor 4 are accommodated between the base 51 and the lid 52. An internal space S which is an airtight space is formed. Such a package 5 is preferably in a reduced pressure (vacuum) state. As a result, the influence of the temperature change outside the package 5 on the light emitting element 3 and the temperature sensor 4 in the package 5 can be reduced, and temperature fluctuations of the light emitting element 3 and the temperature sensor 4 in the package 5 can be reduced. it can. Note that the inside of the package 5 does not have to be in a reduced pressure state, and an inert gas such as nitrogen, helium, or argon may be sealed therein.

  The constituent material of the base 51 is not particularly limited, but is a material having an insulating property and suitable for making the internal space S an airtight space, such as oxide ceramics such as alumina, silica, titania, zirconia, etc. Various ceramics such as nitride ceramics such as silicon nitride, aluminum nitride, and titanium nitride, and carbide ceramics such as silicon carbide can be used.

  In addition, the base 51 has a step portion 512 that is formed on the opening side of the bottom surface of the recess 511 and surrounding the outer periphery of the bottom surface of the recess 511. On the step portion 512, a plurality of connection electrodes (internal electrodes) (not shown) are provided. These connection electrodes are electrically connected to a plurality of external mounting electrodes 61 provided on the outer surface (the lower surface in the figure) of the base 51 through through electrodes (not shown) that penetrate the base 51. .

  The constituent material of the external mounting electrode 61 and the like is not particularly limited. For example, gold (Au), gold alloy, platinum (Pt), aluminum (Al), aluminum alloy, silver (Ag), silver alloy, chromium (Cr ), Chromium alloy, nickel (Ni), copper (Cu), molybdenum (Mo), niobium (Nb), tungsten (W), iron (Fe), titanium (Ti), cobalt (Co), zinc (Zn), A metal material such as zirconium (Zr) can be used.

  A frame-like (annular) seal ring 53 is provided on the end surface of the base 51 on the lid 52 side. The seal ring 53 is made of a metal material such as Kovar, and is joined to the base 51 by brazing or the like. The lid 52 is joined to the base 51 through the seal ring 53 by seam welding or the like.

  The lid 52 includes a plate-shaped main body 54, a cylindrical protrusion 55 provided on the main body 54, and a window that closes a hole 551 (opening) formed inside the protrusion 55. 56.

  The constituent material of the main body 54 is not particularly limited, but a metal material is preferably used, and among these, it is preferable to use a metal material whose linear expansion coefficient approximates that of the constituent material of the base 51. Therefore, for example, when the base 51 is a ceramic substrate, it is preferable to use an alloy such as Kovar as the constituent material of the main body 54.

  The projecting portion 55 has a hole 551 communicating with the hole 541 of the main body portion 54 described above, and a hole 552 communicating with the hole 551 on the opposite side of the hole 551 from the hole 541. Have. Each of the holes 551 and 552 allows at least a part of the light LL from the light emitting element 3 to pass therethrough. Here, the width (diameter) of the hole 552 is larger than the width (diameter) of the hole 551, whereby a stepped portion 553 is formed between the hole 551 and the hole 552. The step 553 is parallel to the plate surface of the main body 54 described above. The step portion 553 may be inclined with respect to the plate surface of the main body portion 54.

  The constituent material of the projecting portion 55 may be different from the constituent material of the main body portion 54, but it is preferable to use a metal material whose linear expansion coefficient approximates that of the constituent material of the main body portion 54. More preferably, it is the same as the constituent material. Further, the projecting portion 55 is formed separately from the main body portion 54, and may be joined (fixed) by a known joining method, or may be integrated (collectively) with the main body portion 54 using a mold or the like. It may be formed.

  In such a package 5, a window 56 made of a plate-like member that transmits the light LL is installed inside the hole 552. The window portion 56 is joined to the step portion 553 described above by a known joining method, and closes the opening on the hole 552 side of the hole 551 of the protruding portion 55 described above. Here, as described above, the stepped portion 553 is parallel to the plate surface 540 of the main body portion 54, and accordingly, the surface of the window portion 56 on the light emitting element 3 side is also the plate surface of the main body portion 54. It is parallel to 540. In addition, the window part 56 may be inclined with respect to the plate surface of the main body part 54 similarly to the step part 553 described above.

  Although it does not specifically limit as a constituent material of the window part 56, For example, various glass materials etc. are mentioned. The window part 56 may be an optical component having functions such as a lens and a neutral density filter.

  Such a lid 52 is positioned by engaging the main body portion 54 and the protruding portion 55 with a holder 304 of the optical system unit 30 described later. More specifically, the lid 52 is positioned in the emission direction of the light LL by the plate surface of the main body 54 coming into contact with the positioning surface 306 of the holder 304. Further, the side surface of the protruding portion 55 abuts against the inner wall surface of the through hole 305 in a state where the protruding portion 55 is inserted into the through hole 305 of the holder 304, whereby the lid 52 is positioned in the light LL emission direction. . In addition, since the main body 54 and the protrusion 55 come into contact with the holder 304 in this manner, the temperature of the lid 52 can be reduced by the heat radiation from the heat radiating holder 304 made of a metal material.

  The Peltier element 2 is disposed on the bottom surface of the concave portion 511 of the base 51 of such a package 5. The Peltier element 2 is fixed to the base 51 with, for example, an adhesive. The Peltier element 2 includes a pair of substrates 21 and 22 and a joined body 23 provided between the substrates 21 and 22. The substrates 21 and 22 are each made of a material having excellent thermal conductivity such as a metal material or a ceramic material. In addition, an insulating film is provided on the surfaces of the substrates 21 and 22 as necessary.

  Such a Peltier element 2 is electrically connected to a connection electrode (not shown) provided on the package 5 via a wiring (a wiring including a bonding wire) (not shown). In the Peltier element 2, one of the substrates 21 and 22 is the heat generation side and the other is the heat absorption side due to the Peltier effect generated in the joined body 23 by energization. Here, the Peltier element 2 has a state in which the substrate 21 is on the heat generation side and the substrate 22 is on the heat absorption side, and a state in which the substrate 21 is on the heat absorption side and the substrate 22 is on the heat generation side, depending on the direction of the supplied current. And can be switched. Therefore, even if the range of environmental temperature is wide, the temperature of the light emitting element 3 and the like can be adjusted to a desired temperature (target temperature). Thereby, the bad influence (for example, wavelength fluctuation of light LL) by a temperature change can be reduced more. Here, the target temperature of the light-emitting element 3 is determined according to the characteristics of the light-emitting element 3 and is not particularly limited, but is, for example, about 30 ° C. or more and 40 ° C. or less.

  The light emitting element 3 is, for example, a semiconductor laser such as a vertical cavity surface emitting laser (VCSEL). A semiconductor laser can emit two types of light having different wavelengths by superimposing (modulating) a high-frequency signal on a DC bias current. In this embodiment, the light emitted from the light emitting element 3 is linearly polarized. The light emitting element 3 is electrically connected to a connection electrode (not shown) provided on the package 5 via a wiring (a wiring including a bonding wire) (not shown).

  The temperature sensor 4 is a temperature detection element such as a thermistor or a thermocouple, for example. The temperature sensor 4 is electrically connected to a connection electrode (not shown) provided on the package 5 via a wiring (a wiring including a bonding wire) (not shown).

(Optical unit)
As shown in FIG. 2, the optical system unit 30 includes a neutral density filter 301, a condenser lens 302, a quarter-wave plate 303, and a holder 304 that holds them. Here, the holder 304 has a through-hole 305 opened at both ends. The through-hole 305 is a light LL passage region, and the neutral density filter 301, the condenser lens 302, and the quarter-wave plate 303 are arranged in this order in the through-hole 305. As shown in FIG. 3, the neutral density filter 301, the condensing lens 302, and the quarter wavelength plate 303 are each fixed to the holder 304 with an adhesive or the like (not shown). Such a holder 304 is made of, for example, a metal material such as aluminum and has heat dissipation.

  As described above, the neutral density filter 301 has a function of reducing the intensity of the light LL from the light emitting element 3 described above. The neutral density filter 301 is not particularly limited, and may be either an absorption type or a reflection type. The condensing lens 302 has a function of adjusting the radiation angle of the light LL (for example, bringing the light LL closer to parallel light). Thereby, it is possible to reduce the change in the power density of the light LL in the traveling direction in the atomic cell 201 and to suppress the expansion of the line width of the EIT signal. As a result, the oscillation characteristics (particularly short-term frequency stability) of the atomic oscillator 1 can be improved. The quarter-wave plate 303 has a function of converting two types of light having different frequencies included in the light LL from linearly polarized light to circularly polarized light (right circularly polarized light or left circularly polarized light). Thereby, the strength of the EIT signal can be increased by the interaction with the magnetic field from the coil 205.

  The optical system unit 30 can omit the neutral density filter 301 depending on the intensity of the light LL from the light emitting element 3 or the like. The optical system unit 30 may include optical elements other than the neutral density filter 301, the condenser lens 302, and the quarter wavelength plate 303. Further, the order of arrangement of the neutral density filter 301, the condensing lens 302, and the quarter wavelength plate 303 is not limited to the order shown in the figure, and is arbitrary. Further, the postures of the neutral density filter 301, the condensing lens 302, and the quarter wavelength plate 303 are arbitrary.

(Atomic cell unit)
The atomic cell unit 20 includes an atomic cell 201, a light receiving element 202, a heater 203, a temperature sensor 204, a coil 205, and a package 206 that houses these.

  In the atomic cell 201, gaseous alkali metals such as rubidium, cesium, and sodium are sealed. Further, in the atomic cell 201, a rare gas such as argon or neon, or an inert gas such as nitrogen may be sealed together with an alkali metal gas as a buffer gas, if necessary.

  The atomic cell 201 includes a body portion 2011 having a columnar through-hole and a pair of window portions 2012 and 2013 forming an airtightly sealed internal space by sealing both openings of the through-hole of the body portion 2011. And having. Here, the light LL incident into the atomic cell 201 is transmitted through one window portion 2012, and the light LL emitted from the atomic cell 201 is transmitted through the other window portion 2013. Accordingly, the constituent material of each of the windows 2012 and 2013 is not particularly limited as long as it has transparency to the light LL, and examples thereof include glass materials and quartz. On the other hand, the constituent material of the body portion 2011 is not particularly limited, and examples thereof include a metal material, a glass material, a silicon material, and a crystal. From the viewpoint of workability and bonding with the windows 2012 and 2013, a glass material. It is preferable to use a silicon material. Moreover, as a joining method of the body part 2011 and each window part 2012, 2013, it is determined according to these constituent materials, and is not particularly limited. For example, a direct joining method, an anodic joining method, a melt joining method, and the like. An optical joining method or the like can be used.

  The light receiving element 202 is disposed on the side opposite to the light emitting element module 10 with respect to the atomic cell 201. The light receiving element 202 is not particularly limited as long as it can detect the intensity of the light LL (resonant light pair) transmitted through the atomic cell 201. For example, a photodetector (light receiving element) such as a photodiode. Is mentioned.

  Although not shown, the heater 203 is, for example, disposed on the above-described atomic cell 201 or connected to the atomic cell 201 via a thermally conductive member such as metal. The heater 203 is not particularly limited as long as the atomic cell 201 (more specifically, an alkali metal in the atomic cell 201) can be heated. Examples of the heater 203 include various heaters having a heating resistor, Peltier elements, and the like. It is done.

  Although not shown, the temperature sensor 204 is disposed in the vicinity of the atomic cell 201 or the heater 203, for example. The temperature sensor 204 is not particularly limited as long as the temperature of the atomic cell 201 or the heater 203 can be detected. Examples of the temperature sensor 204 include various known temperature sensors such as a thermistor and a thermocouple.

  Although not shown, the coil 205 is, for example, a solenoid type coil wound around the outer periphery of the atomic cell 201 or a pair of Helmholtz type opposed via the atomic cell 201. The coil 205 generates a magnetic field in the atomic cell 201 in a direction (parallel direction) along the optical axis of the light LL. Thereby, the gap between different energy levels in which the alkali metal atoms in the atomic cell 201 are degenerated can be widened by Zeeman splitting to improve the resolution and reduce the line width of the EIT signal. Note that the magnetic field generated by the coil 205 may be either a DC magnetic field or an AC magnetic field, or may be a magnetic field in which a DC magnetic field and an AC magnetic field are superimposed.

  Although not shown, the package 206 includes, for example, a plate-like base and a lid joined to the base, and the above-described atomic cell 201, light receiving element 202, heater 203, and temperature sensor are interposed therebetween. An airtight space for housing 204 and the coil 205 is formed. Here, the substrate directly or indirectly supports the atomic cell 201, the light receiving element 202, the heater 203, the temperature sensor 204, and the coil 205. A plurality of terminals electrically connected to the light receiving element 202, the heater 203, the temperature sensor 204, and the coil 205 are provided on the outer surface of the base. On the other hand, the lid has a bottomed cylindrical shape with one end opened, and the opening is closed by the base. In addition, a window portion 207 having transparency to the light LL is provided at the other end portion (bottom portion) of the lid.

  The constituent material of the package 206 other than the base body and the window portion 207 of the lid is not particularly limited, and examples thereof include ceramics and metals. Moreover, as a constituent material of the window part 207, a glass material etc. are mentioned, for example. The method for joining the base and the lid is not particularly limited, and examples thereof include brazing, seam welding, energy beam welding (laser welding, electron beam welding, etc.) and the like. Further, the inside of the package 206 is preferably depressurized from the atmospheric pressure. Thereby, the temperature of the atomic cell 201 can be controlled easily and with high accuracy. As a result, the characteristics of the atomic oscillator 1 can be improved. Note that the window portion 207 may be omitted when the package 206 is not an airtight space.

(Support member)
The support member 40 has a plate shape, and the atomic cell unit 20 and the optical system unit 30 described above are placed on one surface thereof. The support member 40 has an installation surface 401 that follows the shape of the lower surface of the holder 304 of the optical system unit 30. A stepped portion 402 is formed on the installation surface 401. The step portion 402 engages with the step portion on the lower surface of the holder 304 to restrict the holder 304 from moving to the atomic cell unit 20 side (right side in FIG. 2). Similarly, the support member 40 has an installation surface 403 along the shape of the lower surface of the package 206 of the atomic cell unit 20. A stepped portion 404 is formed on the installation surface 403. This stepped portion 404 engages with an end surface (the left end surface in FIG. 2) of the package 206 to restrict the package 206 from moving toward the optical system unit 30 (the left side in FIG. 2).

  Thus, the relative positional relationship between the atomic cell unit 20 and the optical system unit 30 can be defined by the support member 40. And since the light emitting element module 10 is being fixed with respect to the holder 304, the relative positional relationship of the light emitting element module 10 with respect to the atomic cell unit 20 and the optical system unit 30 will also be prescribed | regulated. Here, the package 206 and the holder 304 are each fixed to the support member 40 by a fixing member such as a screw (not shown). The support member 40 is fixed to the package 60 by a fixing member such as a screw (not shown). Moreover, the support member 40 is comprised, for example with metal materials, such as aluminum, and has heat dissipation. Thereby, heat dissipation of the light emitting element module 10 can be performed efficiently.

(Controller unit)
As shown in FIG. 3, the control unit 50 includes a circuit board 505, two connectors 506 a and 506 b provided on the circuit board 505, a rigid wiring board 507 a connected to the light emitting element module 10, an atom A rigid wiring board 507b connected to the cell unit 20, a flexible wiring board 508a connecting the connector 506a and the rigid wiring board 507a, and a flexible wiring board 508b connecting the connector 506b and the rigid wiring board 507b. And a plurality of lead pins 509 penetrating the circuit board 505.

  Here, an IC (Integrated Circuit) chip (not shown) is provided on the circuit board 505, and the IC chip serves as the temperature control unit 501, the light source control unit 502, the magnetic field control unit 503, and the temperature control unit 504 described above. Function. The circuit board 505 has a through hole 5051 through which the support member 40 described above is inserted. The circuit board 505 is supported with respect to the package 60 via a plurality of lead pins 509. Each of the plurality of lead pins 509 penetrates the inside and outside of the package 60 and is electrically connected to the circuit board 505.

  In addition, the structure which electrically connects the circuit board 505 and the light emitting element module 10, and the structure which electrically connects the circuit board 505 and the atomic cell unit 20 are the connector 506a, 506b of illustration, and the rigid wiring board 507a. 507b and flexible wiring boards 508a and 508b, other known connectors and wirings may be used.

  The package 60 is made of, for example, a metal material such as Kovar, and has a magnetic shielding property. Thereby, it is possible to reduce the external magnetic field from adversely affecting the characteristics of the atomic oscillator 1. Note that the inside of the package 60 may be decompressed or atmospheric pressure, but is preferably an airtight space.

  In the atomic oscillator 1 as described above, the light LL emitted from the light emitting element 3 passes through the window portion 56, the neutral density filter 301, the condenser lens 302, the quarter wavelength plate 303, and the atomic cell 201 in this order. The light receiving element 202 receives the light. At that time, a part of the light LL is reflected by at least one of the window 56, the neutral density filter 301, the condenser lens 302, the quarter wavelength plate 303, the atomic cell 201, and the light receiving element 202 as return light. When the light is incident on the light emitting element 3 with high intensity, there is a risk of causing output fluctuation (wavelength fluctuation, intensity fluctuation) of the light emitting element 3. Therefore, the atomic oscillator 1 of the present invention has a configuration that can reduce the intensity of such return light. Hereinafter, this configuration will be described in detail.

(Light path of light source)
FIG. 4 is a schematic diagram for explaining an optical path when the light source unit is arranged on the focal point of the condenser lens. FIG. 5 is a schematic diagram for explaining the optical path of the atomic oscillator shown in FIG. 2 (when the light source unit is arranged at a position shifted from the focal point of the condensing lens). FIG. 6 is a graph showing the relationship between the distance (position) from the optical axis shown in FIGS. 4 and 5 and the intensity of the return light (return light considering only the light collected by the condenser lens).

  As described above, the condensing lens 302 reduces the change in the power density of the light LL in the traveling direction in the atomic cell 201 by bringing the light LL closer to parallel light, and the oscillation characteristics of the atomic oscillator 1 (particularly, This contributes to improving short-term frequency stability.

  However, as in the case of the atomic oscillator 1X shown in FIG. 4 (comparative example), when the light LL emitted from the condenser lens 302 becomes parallel light (optical path indicated by a solid line), that is, the light emitting portion (light) of the light emitting element 3 When the position P of the light emitting element 3 side of the condenser lens 302 coincides with the focal point F that is the focal point of the condenser lens 302 on the light emitting element 3 side, When reflected by the light receiving element 202, the return light LL1, which is the reflected light, returns on the same optical path as the original optical path (optical path indicated by a solid line) and is collected at the focal point F. That is, in this case, the focal point P1 (beam waist) of the return light LL1 coincides with the focal point F. Therefore, in the case shown in FIG. 4, there is a problem that the return light LL <b> 1 enters the light emitting portion of the light emitting element 3 with high intensity, and the output fluctuation of the light emitting element 3 occurs.

  Therefore, as shown in FIG. 5, the atomic oscillator 1 is configured such that the light LL emitted from the condenser lens 302 enters the atomic cell 201 in a non-parallel manner. That is, the atomic oscillator 1 is configured such that the position P of the light emitting portion (the portion from which the light LL is emitted) of the light emitting element 3 does not coincide with the focal point F that is the focal point of the condenser lens 302 on the light emitting element 3 side. . More specifically, the position P is shifted from the focal point F in the direction along the optical axis ax of the condenser lens 302. Thus, even if the light LL is reflected by the quarter-wave plate 303, the windows 2012 and 2013 of the atomic cell 201, or the light receiving element 202, the return light LL1 (indicated by a two-dot chain line) that is reflected is emitted. The light beam LL returns on a different optical path from the light LL, and is condensed at a position opposite to the position P with respect to the focal point F (condensing point P1). Therefore, as shown in FIG. 6, the light emitting element 3 is positioned in a low light density region shifted in the optical axis ax direction from the condensing point P <b> 1 of the return light LL <b> 1. The intensity of the return light (a indicated by a two-dot chain line in FIG. 6) is significantly smaller than that of the atomic oscillator 1X described above (b indicated by a solid line in FIG. 6). Note that “the portion from which the light LL of the light emitting element 3 (light source unit) emits” is an end surface on the side of the resonator that the light emitting element 3 (light source unit) emits light LL. The horizontal axis in FIG. 6 is based on the center (0) of the portion of the light emitting element 3 (light source unit) from which the light LL is emitted.

  As shown in FIG. 5, in the present embodiment, the position P of the light emitting element 3 is located on the condenser lens 302 side with respect to the focal point F of the condenser lens 302. Therefore, the condensing point P <b> 1 is located on the opposite side of the condensing lens 302 with respect to the position P of the light emitting element 3. Thereby, the light LL is diverged (non-parallel) and emitted from the condenser lens 302 toward the atomic cell 201 side. Note that the position P of the light emitting element 3 may be located on the opposite side of the condenser lens 302 with respect to the focal point F of the condenser lens 302. In this case, the condensing point P <b> 1 is located on the condensing lens 302 side with respect to the position P of the light emitting element 3. As a result, the light LL is converged (non-parallel) and emitted from the condenser lens 302 toward the atomic cell 201 side. Here, the spot diameter of the return light LL1 in the plane h perpendicular to the optical axis ax and passing through the position P is such that the position P of the light emitting element 3 is located on the condenser lens 302 side with respect to the focal point F of the condenser lens 302. In this case, the position P of the light emitting element 3 is larger than the case where the position P of the light emitting element 3 is located on the side opposite to the condenser lens 302 with respect to the focal point F of the condenser lens 302. Therefore, when the position P of the light emitting element 3 is located on the condenser lens 302 side with respect to the focal point F of the condenser lens 302, the position P of the light emitting element 3 is relative to the focal point F of the condenser lens 302. Thus, it is possible to reduce the incident amount of the return light LL1 to the light emitting element 3 as compared with the case where it is located on the side opposite to the condenser lens 302.

  In the present embodiment, the position P of the light emitting element 3 is located on the optical axis ax of the condenser lens 302. Thereby, the symmetry of the light LL with respect to the optical axis ax can be increased. Therefore, it is easy to make the power density of the light LL in the atomic cell 201 uniform, and as a result, there is an advantage that it is easy to improve the oscillation characteristics (particularly short-term frequency stability) of the atomic oscillator 1. Note that the position P of the light emitting element 3 may be shifted (separated) from the optical axis ax of the condenser lens 302. In this case, the center of the return light LL1 can be shifted from the light emitting element 3, so that the amount of the return light LL1 incident on the light emitting element 3 is reduced even if the distance between the focal point F and the position P is relatively small. can do.

  Thus, the condensing point P1 of the return light LL1 is a position corresponding to the position P of the light emitting element 3 with respect to the focal point F of the condensing lens 302. Further, the parallelism of the light LL emitted from the condenser lens 302 varies depending on the position P of the light emitting element 3 with respect to the focal point F of the condenser lens 302. From such a viewpoint, the distance between the focal point F of the condenser lens 302 and the position P of the light emitting element 3 is the focal length of the condenser lens 302 (the distance between the center of the condenser lens 302 and the focal point F). On the other hand, it is preferably 0.01 times or more and 0.2 times or less, and more preferably 0.05 times or more and 0.1 times or less. Accordingly, it is possible to reduce the incident amount of the return light LL1 to the light emitting element 3 while preferably exhibiting the effect of making the light LL parallel light by the condenser lens 302 described above.

  From the same viewpoint, it is preferable that the light LL emitted from the condenser lens 302 diverges or converges within the range of ± 5 ° (excluding 0 °) with respect to the parallel light in the atomic cell 201. More preferably, the light is diverging or focusing within a range of ± 3 ° (excluding 0 °). Thereby, the intensity (incident amount) of the return light LL1 to the light emitting element 3 can be reduced while exhibiting to some extent the effect of making the light LL parallel light by the condenser lens 302 described above. .

  The positional relationship between the focal point F of the condenser lens 302 and the position P of the light emitting element 3 can be adjusted by changing at least one of the installation position of the light emitting element 3 and the focal length of the condenser lens 302. . Here, the focal length of the condenser lens 302 can be changed by changing the constituent material (refractive index) and the curvature of the condenser lens 302.

  As described above, the light LL emitted from the condensing lens 302 is made non-parallel, that is, the position P of the light emitting element 3 is not matched with the focal point F of the condensing lens 302, thereby returning light to the light emitting element 3. The intensity (incident amount) of LL1 can be reduced. In order to confirm such an effect, the intensity of the return light incident on the light emitting element 3 was measured by simulation. The results are shown in FIGS.

  FIG. 7 shows the relationship between various conditions (A to M) when the transmittance of the neutral density filter is 2% and the intensity of the return light (condensation by the condenser lens and return light in consideration of reflection by other elements). It is a graph which shows. FIG. 8 shows the relationship between various conditions (A to M) when the transmittance of the neutral density filter is 10% and the intensity of the return light (condensation by the condensing lens and return light in consideration of reflection by other elements). It is a graph which shows. FIG. 9 shows various conditions (A to M) when the refractive index of the condenser lens is 1.51 and the intensity of the return light (condensation by the condenser lens and return light in consideration of reflection by other elements). It is a graph which shows a relationship. FIG. 10 is a schematic diagram showing a modification of the atomic oscillator shown in FIG.

  Here, in FIG. 7 to FIG. 9, “A” denotes an antireflection film on any of the window portion 56, the neutral density filter 301, the condenser lens 302, the quarter wavelength plate 303, the atomic cell 201, and the light receiving element 202. The case where (AR coating) is not provided is shown. “B” indicates a case where an antireflection film is provided on the surface of the window 56 on the light emitting element 3 side. “C” indicates a case where an antireflection film is provided on the surface of the neutral density filter 301 on the light emitting element 3 side. “D” indicates a case where an antireflection film is provided on the surface of the condenser lens 302 on the light emitting element 3 side. “E” indicates a case where an antireflection film is provided on the surface of the quarter wavelength plate 303 on the light emitting element 3 side. “F” indicates a case where an antireflection film is provided on the surface of the window portion 2012 of the atomic cell 201 on the light emitting element 3 side. “G” indicates a case where an antireflection film is provided on the light receiving surface of the light receiving element 202. “H” indicates a case where antireflection films are provided on the surface of the window portion 56 on the light emitting element 3 side and on both surfaces of the neutral density filter 301, respectively. “I” indicates a case where an antireflection film is provided on the surface of the window 56 on the light emitting element 3 side and on the surface of the neutral density filter 301 on the light emitting element 3 side. “J” indicates a case where an antireflection film is provided on the surface of the window 56 on the light emitting element 3 side and the surface of the condenser lens 302 on the light emitting element 3 side. “K” indicates a case where an antireflection film is provided on the surface of the window portion 56 on the light emitting element 3 side and on the surface of the quarter wavelength plate 303 on the light emitting element 3 side. “L” indicates a case where an antireflection film is provided on the surface of the window portion 56 on the light emitting element 3 side and the surface of the window portion 2012 of the atomic cell 201 on the light emitting element 3 side. “M” indicates a case where an antireflection film is provided on each of the surface of the window 56 on the light emitting element 3 side and the light receiving surface of the light receiving element 202. Here, the reflectance of each antireflection film is 0.05%.

  As shown in FIGS. 7 and 8, when the refractive index of the condenser lens 302 is 1.51 (“lens n1.51” in the figure), and when the refractive index of the condenser lens 302 is 1.63 Compared to “lens n1.63” in the drawing, the intensity of the return light incident on the light emitting element 3 is small. Here, when the refractive index of the condenser lens 302 is 1.51, the position P of the light emitting element 3 is located on the condenser lens 302 side with respect to the focal point F of the condenser lens 302. In addition, when the refractive index of the condenser lens 302 is 1.63, the position P of the light emitting element 3 coincides with the focal point F of the condenser lens 302.

  Further, as shown in FIGS. 7 and 8, when the conditions “A” to “G” when the refractive index of the condenser lens 302 is 1.51, the antireflection film is provided in the window portion 56. (Condition “B”), it can be seen that the effect of reducing the intensity of the return light incident on the light-emitting element 3 is significant compared to other conditions. Further, comparing the conditions “H” to “M” when the refractive index of the condenser lens 302 is 1.51, an antireflection film is provided on the window portion 56, and the anti-reflection filter 301 further has an antireflection effect. In the case where a film is provided (conditions “H” and “I”), it can be seen that the effect of reducing the intensity of the return light incident on the light emitting element 3 is significant compared to the other conditions.

  As shown in FIG. 9, when the refractive index of the condenser lens 302 is 1.51, the transmittance of the neutral density filter 301 is 10 for the conditions “A” to “G” and “J” to “M”. % (“ND10%” in the figure), the intensity of the return light incident on the light emitting element 3 as compared with the case where the transmittance of the neutral density filter 301 is 2% (“ND2%” in the figure). It can be seen that the effect of reducing is remarkable. On the other hand, for the conditions “H” and “I”, when the transmittance of the neutral density filter 301 is 2% (“ND 2%” in the figure), the transmittance of the neutral density filter 301 is 10%. It can be seen that the effect of reducing the intensity of the return light incident on the light emitting element 3 is more remarkable than in the case (“ND 10%” in the figure).

  Therefore, when an antireflection film is provided on the window 56 and no antireflection film is provided on the neutral density filter 301 (condition “B”), the intensity of the return light incident on the light emitting element 3 is effectively reduced. It is preferable to decrease the output intensity of the light emitting element 3 and increase the transmittance of the neutral density filter 301. In other words, when the output intensity of the light emitting element 3 is relatively small and the transmittance of the neutral density filter 301 is comparatively large, an antireflection film is provided on the window 56 and the antireflection film is provided on the neutral density filter 301. (Condition “B”) is preferable, whereby the intensity of the return light incident on the light emitting element 3 can be effectively reduced.

  On the other hand, when an antireflection film is provided on both the window 56 and the neutral density filter 301 (conditions “H” and “I”), the intensity of the return light incident on the light emitting element 3 is effectively reduced. It is preferable to increase the output intensity of the light emitting element 3 and reduce the transmittance of the neutral density filter 301. In other words, when the output intensity of the light emitting element 3 is relatively large and the transmittance of the neutral density filter 301 is relatively small, an antireflection film is provided on both the window portion 56 and the neutral density filter 301 (condition “ H ”and“ I ”) are preferable, whereby the intensity of the return light incident on the light emitting element 3 can be effectively reduced.

  Further, it can be seen that the conditions “H” and “I” have a remarkable effect of reducing the intensity of the return light incident on the light emitting element 3 as compared with the other conditions. This is because the following a. And b. This is presumed to be due to this reason. a. Since the window part 56 is very close to the light emitting element 3 as compared with other optical elements (the condensing lens 302, the quarter wavelength plate 303, the atomic cell 201, and the light receiving element 202), the reflected light at the window part 56 is different from the other light elements. The influence on the return light to the light emitting element 3 is larger than the reflected light from the optical element. b. Since the intensity of the light LL transmitted through the neutral density filter 301 is greatly attenuated, the reflected light from other optical elements closer to the atomic cell 201 than the neutral density filter has an influence on the return light to the light emitting element 3. Few.

  As described above, the atomic oscillator 1 includes the atomic cell 201 in which an alkali metal is enclosed, the light emitting element 3 that is a “light source” that emits the light LL that irradiates the alkali metal in the atomic cell 201, and the atomic cell. A light receiving element 202 that is a “light receiving portion” that receives the light LL transmitted through 201 and outputs a signal corresponding to the received light intensity, and a “lens” disposed between the light emitting element 3 and the atomic cell 201. A certain condensing lens 302. In particular, the focal point F of the condensing lens 302 is shifted in the optical axis ax direction (optical axis direction) with respect to the portion of the light emitting element 3 that emits the light LL. Thereby, the condensing lens 302 diverges (or focuses) the light LL toward the atomic cell 201, that is, emits the light LL in a non-parallel manner.

  According to such an atomic oscillator 1, the condensing lens 302 disposed between the light emitting element 3 and the atomic cell 201 diverges (or focuses) the light LL from the light emitting element 3 toward the atomic cell 201. (In other words, the light LL has a focal point at a position shifted in the optical axis ax direction with respect to the portion of the light emitting element 3 that emits light), so that the light LL is reflected by the atomic cell 201, the light receiving element 202, etc. However, the reflected light can be condensed at a position different from that of the light emitting element 3 (particularly, the portion that emits the light LL). Therefore, the amount of the reflected light incident on the light emitting element 3 as the return light LL1 can be reduced, and output fluctuation (wavelength fluctuation, intensity fluctuation) of the light emitting element 3 due to the return light LL1 can be reduced. As a result, the frequency characteristics (particularly, short-term frequency stability) of the atomic oscillator 1 can be improved.

  Thus, the condensing lens 302 diverges the light LL toward the atomic cell 201. Thereby, compared with the case where the condensing lens 302 focuses light toward the atomic cell 201, the intensity (incident amount) of the return light LL1 to the light emitting element 3 can be easily reduced.

  In addition, the atomic oscillator 1 includes a neutral density filter 301 disposed between the light emitting element 3 (light source unit) and the condenser lens 302. Thereby, the intensity | strength of the light LL irradiated to the alkali metal in the atomic cell 201 can be optimized easily. Further, since the return light LL1 also passes through the neutral density filter 301, the intensity (incident amount) of the return light LL1 to the light emitting element 3 can be further reduced.

  Here, the neutral density filter 301 preferably contains a substance that absorbs light, that is, is a so-called absorption type neutral density filter. Thereby, it can be reduced that the light LL from the light emitting element 3 is reflected by the neutral density filter 301 and becomes return light.

  Further, it is preferable that a reflection reducing layer 307 that is an antireflection film (such as an optical thin film) is provided on the neutral density filter 301 as in the atomic oscillator 1A shown in FIG. That is, the atomic oscillator 1 is preferably provided with a reflection reducing layer 307 that is disposed on the neutral density filter 301 (on the surface on the light emitting element 3 side in the drawing) and reduces the reflection of the light LL. Thereby, it can be reduced that the light LL from the light emitting element 3 is reflected by the neutral density filter 301 and becomes return light.

  Further, the atomic oscillator 1 includes a package 5 that houses the light emitting element 3 (light source unit), and the package 5 has a window portion 56 through which the light LL is transmitted. Thereby, the temperature of the light emitting element 3 can be adjusted independently of the atomic cell 201, and as a result, the output fluctuation due to the temperature fluctuation of the light emitting element 3 can be easily reduced.

  Further, on the surface of the window 56 closest to the light emitting element 3 among the plurality of optical elements between the light emitting element 3 and the light receiving element 202, as in the atomic oscillator 1 </ b> A shown in FIG. 10, It is preferable that a reflection reduction layer 57 that is an antireflection film (such as an optical thin film) is provided. That is, the atomic oscillator 1 is preferably provided with a reflection reducing layer 57 that is disposed on the surface of the window portion 56 on the light emitting element 3 (light source portion) side and reduces the reflection of the light LL. Thereby, it can reduce that the light LL from the light emitting element 3 reflects in the window part 56, and becomes return light. Here, since the window part 56 of the package 5 that houses the light emitting element 3 is located at a position very close to the light emitting element 3, the light LL from the light emitting element 3 is reflected by the window part 56 as return light. It is easy to enter. Therefore, reducing the reflected light at the window 56 is particularly effective in reducing the amount of return light to the light emitting element 3.

  Further, the window portion 56 may have a dimming function similar to that of the neutral density filter 301. That is, the window part 56 may be a neutral density filter. In this case, it can be reduced that the light LL from the light emitting element 3 is reflected by the neutral density filter and becomes return light. In addition, the neutral density filter 301 provided outside the package 5 can be omitted, and the configuration of the atomic oscillator 1 can be simplified and reduced in cost.

2. Electronic Device The atomic oscillator 1 as described above can be incorporated into various electronic devices. Hereinafter, the electronic apparatus of the present invention will be described.

  FIG. 11 is a diagram showing a schematic configuration when the atomic oscillator of the present invention is used in a positioning system using a GPS satellite.

  A positioning system 1100 shown in FIG. 11 includes a GPS satellite 1200, a base station device 1300, and a GPS receiver 1400.

The GPS satellite 1200 transmits positioning information (GPS signal).
The base station device 1300 receives the positioning information from the GPS satellite 1200 with high accuracy via, for example, the antenna 1301 installed at the electronic reference point (GPS continuous observation station), and the reception device 1302 receives the positioning information. A transmission apparatus 1304 that transmits positioning information via an antenna 1303.

  Here, the receiving device 1302 is an electronic device including the above-described atomic oscillator 1 (light emitting element module 10) of the present invention as its reference frequency oscillation source. In addition, the positioning information received by the receiving device 1302 is transmitted by the transmitting device 1304 in real time.

  The GPS receiver 1400 includes a satellite receiver 1402 that receives positioning information from the GPS satellite 1200 via the antenna 1401, and a base station receiver 1404 that receives positioning information from the base station device 1300 via the antenna 1403. Prepare.

  The receiving device 1302 that is an “electronic device” included in the positioning system 1100 described above includes the atomic oscillator 1. Thereby, the effect (for example, the excellent frequency characteristic) of the atomic oscillator 1 can be enjoyed and the excellent characteristic can be exhibited.

  Note that the electronic apparatus of the present invention is not limited to the above-described ones. For example, a smartphone, a tablet terminal, a watch, a mobile phone, a digital still camera, an ink jet type ejection device (for example, an ink jet printer), a personal computer (a mobile personal computer). , Laptop personal computer), TV, video camera, video tape recorder, car navigation device, pager, electronic organizer (including communication function), electronic dictionary, calculator, electronic game device, word processor, workstation, video phone, TV monitor for crime prevention, electronic binoculars, POS terminal, medical equipment (for example, electronic thermometer, blood pressure monitor, blood glucose meter, electrocardiogram measuring device, ultrasonic diagnostic device, electronic endoscope), fish detector, various measuring devices, instruments ( Example If, vehicle, aircraft, gauges of a ship), flight simulators, terrestrial digital broadcasting, can be applied to a mobile phone base station or the like.

3. Mobile Object FIG. 12 is a diagram showing an example of a mobile object of the present invention.

  In this figure, a moving body 1500 has a vehicle body 1501 and four wheels 1502, and is configured to rotate the wheels 1502 by a power source (engine) (not shown) provided in the vehicle body 1501. In such a moving body 1500, the atomic oscillator 1 is built.

  As described above, the moving object 1500 includes the atomic oscillator 1. Thereby, the effect (for example, the excellent frequency characteristic) of the atomic oscillator 1 can be enjoyed and the excellent characteristic can be exhibited.

  As described above, the atomic oscillator, the electronic device, and the moving body of the present invention have been described based on the illustrated embodiments, but the present invention is not limited to these.

  Moreover, the structure of each part of this invention can be substituted by the thing of the arbitrary structures which exhibit the same function of embodiment mentioned above, and arbitrary structures can also be added.

  In the above-described embodiment, the case where the present invention is applied to an atomic oscillator that resonantly transitions cesium or the like using the quantum interference effect of two types of light having different wavelengths has been described. However, the present invention is not limited to this. In addition, the present invention can be applied to an atomic oscillator that makes a resonance transition of rubidium or the like by utilizing a double resonance phenomenon caused by light and microwaves.

  In the above-described embodiment, the case of having two packages, that is, a package for storing the light source unit and a package for storing the atomic cell and the light receiving unit has been described as an example. You may store in the package of two common internal spaces.

DESCRIPTION OF SYMBOLS 1 ... Atomic oscillator, 1A ... Atomic oscillator, 1X ... Atomic oscillator, 2 ... Peltier element, 3 ... Light emitting element (light source part), 4 ... Temperature sensor, 5 ... Package, 10 ... Light emitting element module, 20 ... Atomic cell unit, DESCRIPTION OF SYMBOLS 21 ... Board | substrate, 22 ... Board | substrate, 23 ... Assembly body, 30 ... Optical system unit, 40 ... Supporting member, 50 ... Control unit, 51 ... Base, 52 ... Lid, 53 ... Seal ring, 54 ... Main-body part, 55 ... Projection , 56 ... Window, 57 ... Reflection reduction layer, 60 ... Package, 61 ... External mounting electrode, 201 ... Atomic cell, 202 ... Light receiving element (light receiving part), 203 ... Heater, 204 ... Temperature sensor, 205 ... Coil, 206: Package, 207: Window, 301: Neutral filter, 302 ... Condensing lens, 303 ... 1/4 wavelength plate, 304 ... Holder, 305 ... Through hole, 306 ... Position Surface: 307: Reflection reduction layer, 401: Installation surface, 402: Stepped portion, 403 ... Installation surface, 404 ... Stepped portion, 501 ... Temperature control unit, 502 ... Light source control unit, 503 ... Magnetic field control unit, 504 ... Temperature Control unit 505... Circuit board 506 a. Connector, 506 b. Connector, 507 a. Rigid wiring board, 507 b. Rigid wiring board, 508 a. Stepped portion, 540 ... Plate surface, 541 ... Hole, 551 ... Hole, 552 ... Hole, 553 ... Stepped portion, 1100 ... Positioning system, 1200 ... GPS satellite, 1300 ... Base station device, 1301 ... Antenna, 1302 ... Receiver device, 1303 ... Antenna, 1304 ... Transmitter, 1400 ... GPS receiver, 1401 ... Antenna, 1 DESCRIPTION OF SYMBOLS 02 ... Satellite receiving part, 1403 ... Antenna, 1404 ... Base station receiving part, 1500 ... Mobile body, 1501 ... Car body, 1502 ... Wheel, 2011 ... Body part, 2012 ... Window part, 2013 ... Window part, 5051 ... Through-hole, F: Focus, LL: Light, LL1: Return light, P: Position, P1: Condensing point, S: Internal space, W: Width, ax: Optical axis, h ... Plane

Claims (11)

An atomic cell encapsulating an alkali metal;
A light source unit that emits light to irradiate the alkali metal;
A light receiving unit that receives the light transmitted through the atomic cell and outputs a signal corresponding to the received light intensity;
A lens disposed between the light source unit and the atomic cell,
The atomic oscillator, wherein the lens diverges or focuses the light toward the atomic cell and emits the light. An atomic cell encapsulating an alkali metal;
A light source unit that emits light to irradiate the alkali metal;
A light receiving unit that receives the light transmitted through the atomic cell and outputs a signal corresponding to the received light intensity;
A lens disposed between the light source unit and the atomic cell,
An atomic oscillator in which a focal point of the lens is shifted in an optical axis direction with respect to a portion of the light source that emits the light.   The atomic oscillator according to claim 1, further comprising a neutral density filter disposed between the light source unit and the lens.   The atomic oscillator according to claim 2, wherein the neutral density filter contains a substance that absorbs the light.   The atomic oscillator according to claim 2, further comprising a reflection reduction layer disposed on the neutral density filter to reduce reflection of the light.   The atomic oscillator according to claim 1, wherein the lens diverges the light toward the atomic cell. A package containing the light source unit;
The atomic oscillator according to claim 1, wherein the package has a window portion through which the light is transmitted.   The atomic oscillator according to claim 7, further comprising a reflection reduction layer that is disposed on a surface of the window portion on the light source unit side and reduces reflection of the light.   The atomic oscillator according to claim 7 or 8, wherein the window portion is a neutral density filter.   An electronic apparatus comprising the atomic oscillator according to claim 1.   A moving body comprising the atomic oscillator according to claim 1.

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