CN102402024A - Integrated electro-optic phase modulator capable of realizing no temperature effect - Google Patents

Abstract

The invention discloses an integrated electro-optical phase modulator capable of realizing no temperature effect. The bottom surface of the shell of the integrated electro-optical phase modulator is equipped with a Peltier refrigerator and a waveguide in sequence from bottom to top. The upper surface of the waveguide is provided with a modulation electrode, a thermometer and a thermometer electrode of the integrated electro-optic phase modulator. Output fiber optic connection, secured by two bar bars. According to the analog output of the thermometer, the invention adjusts the input current of the Peltier refrigerator to obtain the constant temperature control of the integrated electro-optic phase modulator, so that its performance is consistent in different temperature environments. The invention solves the problems of large volume, high cost and difficult use in the background technology.

Description

An Integrated Electro-optic Phase Modulator Realizing No Temperature Effect

technical field

The invention relates to an integrated electro-optic phase modulator, in particular to an integrated electro-optic phase modulator capable of realizing no temperature effect.

Background technique

The integrated electro-optic phase modulator is based on the electro-optic effect, and the phase modulation is obtained by changing the voltage. It usually uses lithium niobate (LiNbQ ₃ ) crystals, mainly because the transmittance of the transparent band from visible light to infrared light in the crystal reaches 98%, and the crystal has good physical and thermal stability. The current integrated electro-optic phase modulator also integrates the depolarizer and the coupler together to form an integrated optical device.

Integrated electro-optic phase modulators generally form interferometers with optical fibers and are widely used in optical fiber sensing. In particular, it is a key component in fiber optic gyroscopes based on the Signac effect. The main parameters of the integrated electro-optic phase modulator include additional loss, splitting ratio, extinction ratio, and half-wave voltage. Fiber optic gyroscopes have high requirements for the latter two, but these parameters of the integrated electro-optical phase modulator are not constant and will be affected by temperature, among which the change of the half-wave voltage will directly affect the scaling factor of the fiber optic gyroscope.

In order to solve the stability problem of the integrated electro-optic phase modulator, there are two commonly used measures. One is to add a feedback loop in the signal processing of the interferometer, and adjust the modulation gain of the response in real time according to the change of the integrated electro-optic phase modulator. This needs to add another loop in the system solution, the system is complicated and brings about the increase of cost; the other is to provide a constant temperature environment for the interferometer at the system level, but this solution means that the volume increases, the cost increases, and it is not easy use.

Contents of the invention

Aiming at the problem that the characteristic parameters of the integrated electro-optic phase modulator vary with temperature, the purpose of the present invention is to provide an integrated electro-optic phase modulator capable of realizing no temperature effect.

Invention principle:

The integrated electro-optic phase modulator is based on the electro-optic effect of the crystal, and lithium niobate crystal LiNbO3 is commonly used as the substrate. Lithium niobate crystals belong to the trigonal crystal system. According to the linear electro-optic effect of Y-waveguide lithium niobate, it adopts the working mode of z-direction passing and lateral voltage application. When an external voltage V is applied, the corresponding phase shift

           (1)

(1)

Among them, γ is the electro-optic coefficient of the crystal, Γ is the effective overlap coefficient of the light field and the electric field, b is the electrode spacing, λ is the wavelength of the transmitted light wave, L is the modulation wavelength length, and n is the refractive index. When Δφ=π, the input voltage at this time is the half-wave voltage Vπ:

                                    (2)

(2)

The integrated electro-optic phase modulator has a series of characteristic parameters, among which the half-wave voltage is the parameter most affected by temperature, and the variation within the entire operating temperature range (-40°C~+65°C) is usually 6%~8%. It can be seen from the above formula that the half-wave voltage of the integrated electro-optic phase modulator is related to the material and manufacturing process of lithium niobate, and the device itself cannot overcome the changes of L, b, ne caused by temperature changes. The most effective and simple way is to control the temperature of its working environment in the integrated electro-optic phase modulator to keep it constant.

A Peltier cooler is a semiconductor device based on the thermoelectric effect. When electric current passes through two dissimilar conductors that are in contact, a temperature difference appears across the conductors. The maximum temperature difference of semiconductor refrigeration depends on its cold junction temperature Tc, thermoelectric coefficient α, thermal conductivity λ and electrical conductivity σ.

(T _h - T _c ) _max =(α ² σ/λ) T _c ² /2 (3)

According to the temperature of the integrated electro-optic phase modulator, changing the driving current of the Peltier cooler and adjusting the conductivity can obtain different ambient temperatures, so as to achieve the purpose of keeping the ambient temperature of the integrated electro-optic phase modulator constant.

The technical scheme adopted in the present invention is:

The bottom surface of the tube shell of the integrated electro-optic phase modulator is equipped with a Peltier cooler and a waveguide in sequence from bottom to top. The two ends of the Peltier cooler are equipped with a positive electrode for the power input of the Peltier cooler, and the power supply of the Peltier cooler is The input ground electrode, the modulation positive electrode of the integrated electro-optic phase modulator, the modulation ground electrode of the integrated electro-optic phase modulator, the modulation negative electrode of the integrated electro-optic phase modulator, the positive electrode of the thermometer power supply input, the thermometer and the thermometer power supply ground electrode, The temperature output electrode of the thermometer, the input optical fiber and the output optical fiber are respectively connected with the waveguide, and two bar blocks are respectively pressed on the two ends of the input optical fiber and the output optical fiber; The power input pin, the thermometer power output pin, and the modulation ground pin of the integrated electro-optic phase modulator are connected, the modulation positive electrode of the integrated electro-optic phase modulator, the modulation ground electrode of the integrated electro-optic phase modulator, and the modulation of the integrated electro-optic phase modulator The negative electrode is respectively connected to the modulation positive pin of the integrated electro-optic phase modulator, the modulation ground pin of the integrated electro-optic phase modulator, and the modulation negative pin of the integrated electro-optic phase modulator. The power input ground electrode of the pasted refrigerator is respectively connected to the positive terminal pin of the power input of the Peltier refrigerator and the power input ground pin of the Peltier refrigerator.

The waveguide is a Y-shaped waveguide or an X-shaped waveguide.

The beneficial effects that the present invention has are:

The invention includes a coupled waveguide made based on lithium niobate crystal, a thermometer with analog output, and a Peltier cooler. According to the analog output of the thermometer, the input current of the Peltier cooler is adjusted to obtain phase modulation of the integrated electro-optic The constant temperature control of the device makes it perform consistently in different temperature environments. The invention solves the problems of large volume, high cost and difficult use in the background technology.

Description of drawings

Figure 1 is the overall package diagram of the integrated electro-optic phase modulator.

Fig. 2 is a schematic diagram of a three-dimensional structure of a chip in an integrated electro-optic phase modulator.

Fig. 3 is a cross-sectional view of the installation of the integrated electro-optic phase modulator chip.

FIG. 4 is a curve diagram of the half-wave voltage of the integrated electro-optical phase modulator chip in the background technology at 20°C to 50°C.

Fig. 5 is a diagram showing the change of the half-wave voltage at a temperature of 20° C. to 50° C. after the integrated electro-optic phase modulator chip adopts temperature adjustment and can realize no temperature effect.

Fig. 6 is a schematic diagram of a temperature regulation loop of an integrated electro-optical phase modulator capable of realizing no temperature effect.

In the figure: 1. Tube shell of integrated electro-optic phase modulator, 2. Waveguide, 3. Thermometer, 4. Peltier cooler, 5. Input optical fiber, 6. Output optical fiber, 7. Bar block, 8. Bar Block, 9, thermometer power input pin, 10, thermometer power output pin, 11, modulation positive pin of integrated electro-optic phase modulator, 12, modulation ground pin of integrated electro-optic phase modulator, 13, integrated electro-optic phase modulation 14. Peltier cooler power input positive pin, 15. Peltier cooler power input ground pin, 16. Modulation positive electrode of integrated electro-optic phase modulator, 17. Integrated electro-optic phase modulator The modulation ground electrode of the phase modulator, 18, the modulation negative electrode of the integrated electro-optic phase modulator, 19, the thermometer power supply input positive electrode, 20, the thermometer power supply ground electrode, 21, the thermometer temperature output electrode, 22, the Peltier refrigerator power supply Input positive electrode, 23, Peltier refrigerator power input ground electrode, 24, Peltier refrigerator controller.

Detailed ways

Below in conjunction with accompanying drawing and embodiment the present invention will be further described:

As shown in Fig. 1, Fig. 2 and Fig. 3, the bottom surface of the shell 1 of the integrated electro-optic phase modulator of the present invention is sequentially equipped with a Peltier refrigerator 4 and a waveguide 2 from bottom to top, and the Peltier refrigerator 4 is two The positive electrode 22 for the power input of the Peltier refrigerator is set at the end, the ground electrode 23 for the power input of the Peltier refrigerator is arranged, and the modulation positive electrode 16 of the integrated electro-optical phase modulator, the modulation ground electrode 17 of the integrated electro-optic phase modulator are arranged on the waveguide 2, The modulation negative electrode 18 of the integrated electro-optic phase modulator, the thermometer power supply input positive electrode 19, the thermometer power supply ground electrode 20, the thermometer temperature output electrode 21 and the thermometer 3, the input optical fiber 5 and the output optical fiber 6 are respectively connected to the waveguide 2, two strips Blocks 7 and 8 are respectively pressed on both ends of the input optical fiber 5 and the output optical fiber 6; the thermometer power input positive electrode 19, the thermometer power ground electrode 20, and the thermometer temperature output electrode 21 are respectively connected to the thermometer power input pin 9 and the thermometer power output pin 10. The modulation ground pin 12 of the integrated electro-optic phase modulator is connected, the modulation positive electrode 16 of the integrated electro-optic phase modulator, the modulation ground electrode 17 of the integrated electro-optic phase modulator, and the modulation negative electrode 18 of the integrated electro-optic phase modulator are respectively connected to the integrated The modulation positive pin 11 of the electro-optic phase modulator, the modulation ground pin 12 of the integrated electro-optic phase modulator, and the modulation negative pin 13 of the integrated electro-optic phase modulator are connected, and the positive electrode 22 of the power input of the Peltier refrigerator is connected. The power input ground electrode 23 of the refrigerator is respectively connected with the power input positive pin 14 of the Peltier refrigerator and the power input ground pin 15 of the Peltier refrigerator.

The waveguide 2 is a Y-shaped waveguide or an X-shaped waveguide.

A waveguide 2 made of a lithium niobate wafer, a thermometer 3 based on a silicon wafer and a Peltier cooler 4 constitute a chip of an integrated electro-optic phase modulator. In terms of waveguide design, there are many shapes of waveguides. The most commonly used one is Y-shaped as shown in Figure 2, also known as Y-waveguide; there are also waveguides of other shapes, such as X-shaped; these can be generated by computer software. The corresponding photolithography mask is produced, and the waveguide and electrode patterns are generated on the wafer and the electronic circuit is generated on the silicon wafer through the standard semiconductor photolithography process. The waveguide is generated by annealing proton exchange technology, and after completion, it is annealed at high temperature. The input and output optical fibers 5, 6 and the Y waveguide are precisely aligned end-to-end, and are fixed with strip blocks 7, 8 made of the same lithium niobate crystal as the waveguide material; the thermometer 3 and the waveguide 2 are permanently bonded with ultraviolet glue Knot solidifies.

The cooling surface of the Peltier cooler 4 and the bottom of the waveguide 2 are bonded with silicone glue to fill the gap between them. On the other side, the heat dissipation surface of the Peltier cooler 4 and the package surface of the integrated electro-optic phase modulator 1 are directly bonded closely with heat-conducting silicone glue. The power supply ground of the thermometer 3 is connected to the modulation ground electrode of the waveguide 2 through a wire.

When in use, the driving current of the Peltier cooler 4 is adjusted according to the output of the thermometer 3 through a hardware circuit or a digital circuit, and the operating temperature of the integrated electro-optic phase modulator is adjusted to achieve constant temperature control of the integrated electro-optical phase modulator and eliminate the integrated electro-optic phase Modulator temperature effects for purposes. The schematic diagram of monitoring and regulation is shown in Figure 6. The input of the Peltier cooler controller 24 is the temperature output from the thermometer 3, generally an analog voltage signal; the output of the Peltier cooler controller 24 is the driving current of the Peltier cooler 4, according to the analog algorithm or The temperature compensation model changes the driving current, adjusts the cooling temperature of the Peltier cooler, and realizes the constant temperature control of the waveguide 2 in the integrated electro-optic phase modulator.

Figure 4 is the variation curve of the half-wave voltage of the integrated electro-optic phase modulator chip in the background technology between 20°C and 50°C. up 1.1%. In contrast, Figure 5 is a temperature-adjusted integrated electro-optic phase modulator chip that can realize the temperature-adjusted half-wave voltage change curve at a temperature of 20°C to 50°C, and the half-wave voltage is between 3.319V and 3.322V Randomly change between, the range of change is 3mV, which is an order of magnitude lower than the range of change in Figure 5.

Claims (2)

1. An integrated electro-optical phase modulator capable of realizing no temperature effect, characterized in that: a Peltier cooler (4) and The waveguide (2), the positive electrode (22) for the power input of the Peltier cooler (4) is arranged at both ends of the Peltier cooler (4), the ground electrode (23) for the power input of the Peltier cooler, and the upper surface of the waveguide (2) is provided with The modulation positive electrode (16) of the integrated electro-optic phase modulator, the modulation ground electrode (17) of the integrated electro-optic phase modulator, the modulation negative electrode (18) of the integrated electro-optic phase modulator, the thermometer (3) and the thermometer power input positive electrode ( 19), thermometer power supply ground electrode (20), thermometer temperature output electrode (21), input optical fiber (5) and output optical fiber (6) are respectively connected to waveguide (2), and two strip blocks (7, 8) are respectively pressed At both ends of the input optical fiber (5) and the output optical fiber (6); the thermometer power input positive electrode (19), the thermometer power ground electrode (20), and the thermometer temperature output electrode (21) are respectively connected to the thermometer power input pin (9) , the thermometer power supply output pin (10), and the modulation ground pin (12) of the integrated electro-optic phase modulator; the modulation positive electrode (16) of the integrated electro-optic phase modulator, and the modulation ground electrode (17) of the integrated electro-optic phase modulator , the modulation negative electrode (18) of the integrated electro-optic phase modulator and the modulation positive pin (11) of the integrated electro-optic phase modulator, the modulation ground pin (12) of the integrated electro-optic phase modulator, and the modulation pin (12) of the integrated electro-optic phase modulator Negative pin (13) connected; Peltier refrigerator power input positive electrode (22), Peltier refrigerator power input ground electrode (23) and Peltier refrigerator power input positive terminal pin (14), The power input ground pin (15) of the Peltier cooler is connected. 2. An integrated electro-optical phase modulator capable of realizing no temperature effect according to claim 1, characterized in that: the waveguide (2) is a Y-shaped waveguide or an X-shaped waveguide.

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