JPH012023A - light deflection device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to an optical deflection device that generates surface acoustic waves in an optical waveguide and deflects guided light by the diffraction action of the surface acoustic waves. relates to an optical deflection device that can obtain a wide deflection angle range by combining guided light twice by two surface acoustic waves and once by one surface acoustic wave. .

(Prior Art) Conventionally, as shown in Japanese Patent Application Laid-open No. 183626/1983, light is incident on an optical waveguide formed of a material through which surface acoustic waves can propagate, and the guide propagates within the optical waveguide. A surface acoustic wave is generated in the direction intersecting the wave light, the guided light is Bragg diffracted by the surface acoustic wave, and the diffraction angle (deflection angle) of the guided light is continuously changed by continuously changing the frequency of the surface acoustic wave. A light deflection device that changes the direction of the light is known. Such optical deflection devices include, for example, mechanical optical deflectors such as galvanometer mirrors and polygon mirrors, EOD (electro-optic optical deflectors), and A
Compared to optical deflectors that use optical deflection elements such as OD (f-acoustic optical deflectors), they have the advantage of being smaller and lighter, and are highly reliable as they do not have mechanical moving parts. are doing.

(Problems to be Solved by the Invention) However, the above-described optical deflection device has a problem in that it is difficult to obtain a large deflection angle.

In other words, in an optical deflection device using this optical waveguide, the optical deflection angle is approximately proportional to the frequency of the surface acoustic waves, so in order to obtain a large deflection angle, it is necessary to increase the frequency of the surface acoustic waves to an extremely high value. It will be necessary to change. Furthermore, in addition to changing the frequency of the surface acoustic waves over a wide band in this way, in order to satisfy the Bragg condition, the traveling direction of the surface acoustic waves is continuously changed (steering). It is necessary to control the angle of incidence on the

In order to meet the above requirements, for example,
As shown in Japanese Patent No. 183628, multiple interdigitated electrode pairs (IDT: InterD 1g1ta) generate surface acoustic waves whose frequencies change in different bands.
An optical deflection device has been proposed in which IDTs are arranged such that surface acoustic wave generation directions differ from each other, and each IDT is operated by switching.

However, the optical deflection device with the above configuration has a problem in that the diffraction efficiency decreases around the crossover frequency of the surface acoustic waves emitted by each IDT, so the amount of light of the deflected light beam fluctuates depending on the deflection angle. occurs.

Furthermore, even with the above configuration, the IDT having a portion with a high deflection angle must be configured to generate a surface acoustic wave of an extremely high frequency. This point will be explained below using a specific example. When the incident angle of the guided light with respect to the traveling direction of the surface acoustic wave is θ, the deflection angle δ of the guided light due to the acousto-optic interaction between the surface acoustic wave and the guided light is δ−20. If the wavelength and effective refractive index of the guided light are λ and Ne, and the wavelength, frequency, and velocity of the surface acoustic wave are Δ, f, and v, respectively, then 2θ−2sin'(λ/2Ne −A) ~ λ/N c.
・Δ−λ・f/Nc・■・・・(1). Therefore, the deflection angle range △(2θ) is △(2θ) − △f・λ/
It becomes Ne−■. Here, for example, λ-0,78μ771. Ne-2
．． 2, deflection angle range Δ as v -350077L/s
In order to obtain (2θ)-io', the frequency range of the surface acoustic wave, that is, the frequency band of the high frequency applied to the IDT △
f = 1.72 GHz is required. If this frequency band is set to one octave so as not to be affected by the second-order diffracted light, the center frequency f(, -2,57 GHz.

The maximum frequency is f2-3.43 GHz. The period A of the IDT that obtains this maximum frequency f2 is -1.02 .mu.m, and the line width of the IDT electrode finger is W-A/4-0.255 .mu.m.

In the photolithography method and electron beam lithography, which are common techniques for forming IDTs, the current line width limits are approximately 0.8 μm and 0.5 μm, respectively, and therefore IDTs with extremely small line widths as described above. is difficult to realize. Furthermore, even if such a fine IDT could be formed in the future, a driver that generates a high frequency of about 3.43 GHz would be difficult to manufacture and extremely expensive, and such a fine IDT would require a high voltage. It becomes difficult to apply. Furthermore, if the frequency of the surface acoustic wave is increased as described above, the wavelength will naturally become shorter, so the surface acoustic wave will be more easily absorbed by the optical waveguide, resulting in a decrease in diffraction efficiency.

On the other hand, the literature
s on C1rcuUs and 5yste
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12, p1072 [Guided-Wave
AcoustoopticBragg Module
ators ror Wide-Band Inte
gratcd 0pNcCommunication
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cessing] by C, S, TSA I, as mentioned above, multiple IDTs are not operated by switching, but one IDT is a curved finger whose electrode finger line width changes continuously and each electrode finger has an arc shape. An optical deflection device configured as a chirped IDT is shown in which the frequency and traveling direction of surface acoustic waves are continuously changed over a wide range using this single IDT. In such a configuration, the problem of the amount of light beam fluctuating depending on the deflection angle as described above can be solved, but the problem remains that the frequency of the surface acoustic wave must be set extremely high. , which causes exactly the same problem as described above.

Therefore, the present inventors have previously proposed an optical deflection device that does not cause the above-mentioned fluctuation in the light intensity of the light beam and can obtain a wide deflection angle range without setting the frequency of the surface acoustic wave to be extremely high. (Gan Sho 61-283648).

As described above, this optical deflection device allows guided light to travel through an optical waveguide formed of a material that allows surface acoustic waves to propagate.
In an optical deflection device that diffracts and deflects the guided light using a surface acoustic wave, a first surface acoustic wave that travels in a direction intersecting the optical path of the guided light and diffracts and deflects the guided light is applied to the optical waveguide. a first surface acoustic wave generating means for generating; 7- Proceeding in a direction intersecting the optical path of the guided wave diffracted as described above, diffracting and deflecting the guided light in a direction that further amplifies the deflection due to the diffraction; a second surface acoustic wave generating means for generating a second surface acoustic wave in the optical waveguide;
The wave number vectors of the guided light before and after being diffracted by the second surface acoustic wave are lk, lk2, and the wave number vectors of the guided light diffracted by the second surface acoustic wave are respectively 3 and 1.
, the wave number vector of the second surface acoustic wave is lKt, 1 to 2
The first and second surface acoustic waves are formed so as to continuously change their frequencies and traveling directions while satisfying the following conditions: J + lK1-1 = 2 IJ + IKz-1 = 3. It is something to do.

The first and second surface acoustic wave generating means described above are, for example, a pair of tilted chirped interdigitated comb-shaped electrodes (T
1lted-Finger ChirpedID
T) and a driver that applies an alternating voltage whose frequency changes continuously to this electrode pair.

In the above configuration, since the guided light that has been deflected by the first surface acoustic wave is deflected again by the second surface acoustic wave, the frequency bands of each of the first and second surface acoustic waves are set to be very wide. Even without this, a wide deflection angle range can be obtained as a whole.

The present invention is based on the patent application filed in 1981-28 having the above-mentioned features.
It is an object of the present invention to further develop the optical deflection device of No. 3848 and to provide an optical deflection device that can obtain a wider deflection angle range.

(Means for Solving the Problems) The optical deflection device of the present invention is the optical deflection device disclosed in Japanese Patent Application No. 61-283648, which includes an optical waveguide as described above, a first surface acoustic wave generating means, and a second surface acoustic wave generating means. In this optical deflection device, a deflection angle range δ2 to δ3'(δz<δ3) is obtained by twice diffraction of the guided light, and the deflection angle is smaller than this lower limit deflection angle δ2. In the range in which δ1
<δ2) is characterized in that it is configured to deflect continuously in the range of <δ2).

(Function) When a light beam is deflected by the light deflection device having the above configuration, the deflection angle range is expanded to the lower angle side, compared to the case where the light beam is deflected only by two-time diffraction.

In this case, the deflection angle δ2. Depending on the setting of δ3,
In the expanded low deflection angle range, guided light that cannot be diffracted by the second surface acoustic wave during second diffraction will proceed. In other words, unnecessary light is generated within the deflection angle range that is intended to be used as an effective scanning range. However, the diffraction efficiency of surface acoustic waves can currently be secured at around 90%, so if the amount of guided light before intersecting with the first surface acoustic wave is 1, the amount of twice-diffracted light used for optical scanning is Light intensity is 0
．． 9 Xo, 9-0.81. On the other hand, the amount of unnecessary light above is 0
. , 9
For example, although it is difficult to record high-gradation images, it is quite possible to record binary images using photosensitive materials that are currently in practical use.

(Example) Hereinafter, the present invention will be described in detail based on an example shown in the drawings.

FIG. 1 shows an optical deflection device according to an embodiment of the present invention. This optical deflection device IO includes an optical waveguide 12 formed on a substrate 11 and a condensing diffraction grating (F oeustlg) for light beam incidence formed on the optical waveguide 12.
grating coupler (hereinafter referred to as FCC) 13, a light beam output FGC 14, and a surface acoustic wave 15.1B that travels in a direction intersecting the optical path of the guided light that travels between these FCCs 13 and 14. The first and second inclined finger chirps are generated by a pair of interdigitated interdigitated electrodes (T1ted-Flnger Chirpe).
d InterD 1g1tal T ransd
ucer, hereinafter referred to as inclined finger chive IDT) 17
．． 18, a high frequency amplifier 19 that applies a high frequency alternating voltage to T17.18 from these inclined finger chirps in order to generate the surface acoustic waves 15.16, and continuously changes (sweeps) the frequency of the voltage. It has a sweeper 20.

In addition, a second inclined finger chirp IDT18 and a high frequency amplifier I
A swing switch 30 is provided between the IDT 9 and the IDT 8 to appropriately cut off the application of an alternating voltage to the IDT 8, and this switch 30 is opened and closed by a control circuit 31 in synchronization with the frequency sweep timing of the sweeper 20. It looks like this.

In this embodiment, as an example, the substrate 11 has LiNbO
The optical waveguide 12 is formed by using three wafers and providing a Ti diffusion film on the surface of the wafer. Note that substrate 1
1 may also be a crystalline substrate made of sapphire, Si, or the like. Furthermore, the optical waveguide 12 is not limited to the above-mentioned Ti diffusion, but can also be formed by sputtering or vapor depositing other materials on the substrate II. Regarding optical waveguides, for example, Ta1Ilr (T, Ta1Ilr
) ed. “Ingrated Optics (I nte
rated 0ptics ) J (Topics in Applied Physics (Topics
in Applied Physics) Volume 7) Springer-
Verlag) (1,975), Nishihara, Haruna,
A detailed description can be found in published works such as "Optical Integrated Circuits" by Suhara, published by Ohmsha (1985), and any of these known optical waveguides can be used as the optical waveguide 12 in the present invention.

However, this optical waveguide I2 must be formed from a material such as the above-mentioned Ti diffusion film that allows surface acoustic waves to propagate, which will be described later. Further, the optical waveguide may have a laminated structure of two or more layers.

The inclined finger chirp IDT17.18 is, for example, an optical waveguide 1.
A positive electron beam resist is applied to the surface of 2, an Au conductive thin film is further deposited on top of it, an electrode pattern is drawn with an electron beam, the Au thin film is peeled off and developed, and then a Cr thin film and an AI thin film are deposited. After that, it can be formed by performing lift-off in a six-layer solvent. Incidentally, when the substrate 11 and the optical waveguide 12 are made of a piezoelectric material, the inclined finger chirp IDTL 7.18 generates a surface acoustic wave 15.16 even if it is installed directly inside the optical waveguide 12 or on the substrate 11.
However, if this is not the case, a piezoelectric thin film made of, for example, ZnO may be formed on a part of the substrate 11 or the optical waveguide 12 by vapor deposition, sputtering, etc., and the IDTL 7.18 may be installed there. .

The light beam L to be deflected is emitted from a light source 21, such as a semiconductor laser, toward the FGC13.

This light beam L (divergent beam) is made into a parallel beam by the FGCL 3 and then taken into the optical waveguide 12,
Wave is guided within the optical waveguide 12. This waveguide light is the first
Due to the acousto-optic interaction with the first surface acoustic wave 15 emitted from the inclined finger chirp IDT 17, it is diffracted (B rag diffraction) as shown in the figure.

The guided light L2 diffracted and deflected in this way is transferred to the switch 3.
0 is closed and an alternating voltage is applied to the second tilted finger chirp IDT 18, the above deflection is further amplified by acousto-optic interaction with the second surface acoustic wave 1B emitted from this IDT 18. Diffract in the direction. As described above, since the frequency of the alternating voltage applied to the first inclined finger chirp IDT 17 changes continuously, the frequency of the first surface acoustic wave 15 changes continuously. As is clear from the above equation (1), the deflection angle of the guided light L2 diffracted by the surface acoustic wave 15 is approximately proportional to the frequency of the surface acoustic wave 15.
By changing the frequency of , the guided light L2 is continuously deflected as shown by arrow A. This guided light L2 is then deflected by the second surface acoustic wave 16, but since the frequency of this second surface acoustic wave 1B also changes continuously like the first surface acoustic wave 15, the second The guided light L3 after passing through the surface acoustic wave 16 is continuously deflected as shown by arrow B.

As will be described in detail later, the alternating voltage output from the high frequency amplifier 19 is continuously swept by the sweeper 20 from the maximum frequency to the minimum frequency, and after the minimum frequency, it is returned to the maximum frequency and the same sweep is repeated. However, the aforementioned control circuit 31 opens the switch 30 during every other sweep described above. That is, when the swept alternating voltage is applied to IDTLs 7 and 18, this alternating voltage is then applied only to the first IDT 17, and then to both IDTs 17 and 18 as described above. 4 is repeated. Therefore, as described above, the guided light L1 is transmitted to the first and second surface acoustic waves 15.
Since the surface acoustic wave 16 is no longer generated after being diffracted and deflected by the surface acoustic wave 16, the guided light L1 is deflected only by the first surface acoustic wave 15, and then the guided light L1 is deflected by the first and second surface acoustic waves 15 again. Deflected by .16. Note that the deflection angle range of the guided light L1 caused only by the first surface acoustic wave 15 and the deflection angle range of the guided light L1 caused by the first and second surface acoustic waves 15.1G are adjacent to each other. The final deflection angle range is the sum of these two deflection angle ranges (this point will be explained in detail later).

Guided light L deflected only by the first surface acoustic wave 15
The guided light L3 deflected by the second surface acoustic wave I5.1B or the first and second surface acoustic waves I5.1B is emitted to the outside of the optical waveguide 12 by the FGC14, and is focused at one point by its condensing action.

Next, the deflection angle range Δδ of the light beam L emitted from the optical waveguide 12 will be explained with reference to FIG. FIG. 2 shows the detailed shape and arrangement of the first slanted finger chirp IDT17 and the second slanted finger chirp IDT18. First slanted finger chirp ID as shown
T17 and the second inclined finger chirp ID71g are each formed such that the interval between the electrode fingers changes stepwise at a constant rate of change, and the direction of each electrode finger also changes stepwise at a constant rate of change. 1st inclined finger chirp IDT1
7 and the second inclined finger chirp IDT 18 are arranged so that the one with the narrower spacing between the electrode fingers (the upper end in the figure) is located on the guided light side, and as described above, the frequency of the applied voltage is swept. , the upper end of which is the maximum frequency f
2-2 GHz s and the lower end is the minimum frequency fl-
It is designed to generate a surface acoustic wave 15.1B of IGH2. The first inclined finger chirp IDT 17 has electrode fingers at the upper end and the lower end inclined by 3 degrees to each other,
The electrode fingers at the upper end are arranged at an angle of 6'' with respect to the traveling direction of the guided light L1, and the electrode fingers at the lower end are arranged at an angle of 3@. - Inclined finger chirp IDT 18 of the force tube 2
The electrode fingers at the upper end and the lower end are inclined by 9 degrees with respect to the traveling direction of the guided light L1, and the electrode fingers at the lower end are at an angle of 18 degrees with respect to the traveling direction of the guided light L1. are arranged to form an angle.

Note that the ground electrodes of both inclined finger chirp IDTs 17 and 18 may be integrated with each other. Furthermore, regarding the inclined finger chirp IDT as described above, for example, the above-mentioned C, S,
A detailed explanation is given in the literature by TSAI.

2 GHz surface acoustic waves 15.
The diffraction state of the light beam when 1B is emitted is the state shown by ■ in FIG. That is, in this case, the guided light L1 is incident on the 2 GHz surface acoustic wave 15 at an incident angle of 6 degrees, and this angle satisfies the Bragg condition. That is, the wave number vector of the guided light L2 after diffraction of the guided light LL1 is kl and lk2, and the wave number vector of the surface acoustic wave 15 is Xl.
Then, as shown in FIG. 3 (1), Ikl + [Kl -1 becomes 2. In other words, the traveling direction of the diffracted waveguide light L2 is the direction of vector 2 (deflection angle -20-12'
). At this time, a 2 GHz surface acoustic wave! 6 is the second
Since it is excited by the electrode finger at the upper end of the inclined finger chirp IDT 1g in FIG. Guided light L2 for surface acoustic wave 16
The incident angle is also 6°, and since the surface acoustic wave IB has the same wavelength as the surface acoustic wave 15, the Bragg condition is satisfied. That is, if the wave number vector of the guided light L3 after diffraction by the surface acoustic wave 16 is 3, and the wave number vector of the surface acoustic wave 16 is 2, then 1, 21, and 2 are given as shown in FIG. 3(1).
It is blatantly 3. At this time, the guided light L3 with respect to the guided light L1
When the deflection angle of is 63, it is δ3-24°.

From the above state, the frequency of surface acoustic wave 15.16 is 1GH
It is gradually lowered to z. Each wave number vector of surface acoustic waves 15.16 [K 1 , IK 2 magnitude 1lK11
Since 11 Kzl is 2π/A if its wavelength is 8, it is ultimately proportional to the frequency of the surface acoustic wave 15.16. Therefore, the frequency of the surface acoustic wave 15.16 is IGH
When z, the wave number vector lK1 of the surface acoustic wave 15.16
．． The size of 2 in 1 is 1/2 of the frequency when the frequency is 2 GHz.
becomes. Also, in this case, surface acoustic wave 15, surface acoustic wave 1
6, that is, the directions of the wave number vectors IKr and IK2 are the first inclined finger chirp IDT17 and the second inclined finger chirp ID which excite the IGHz surface acoustic wave 15.18.
As mentioned above, the electrode finger part of T18 is 3.
Since it is tilted by 9", 2 GHz surface acoustic wave 15.
3″ each from the direction of the 16 wave number vectors IK1 and IKz
, changes by 9°. Also, in Fig. 3 (1), Bz b
Therefore, when the frequency of the surface acoustic waves 15' and 1B is IGHz, the wave number vectors IK1 and IK2 are as shown in FIG. 3(2). Then, the guided light L at this time
If the deflection angle of the guided light L3 with respect to 1 is δ2, then δ2−
It is 12°.

As explained above, the frequency of the surface acoustic wave 15.16 is I
Even in the case of GHz, the above-mentioned relationship 1, +lKl -1 and 2 1k 2 + IK 2-1k 3 hold true.

The size of the wave number vector lkl, 1lktl, is n·2π/λ (n is the refractive index), where λ is the wavelength of the guided light L1.
Since this wavelength is the same for the guided lights L2 and L3, it is always 1lk x l -11 to 2 l -11 to 3 l, and - the wave number vector IK of the blade surface acoustic wave 15 is 8 times the wavelength. Then, it is 2π/A, and this wavelength is always equal to the wavelength of the surface acoustic wave 16, so 1 lK! l −l [K2 l . In addition, the directions of the wave number vectors IK1 and IK2 are such that the frequency of the surface acoustic wave 15.16 is 2G, as explained earlier.
When changing from Hz to IGHz, each changes at its own constant rate of change. Therefore, the surface acoustic wave 15.18
While the frequency of changes from 2 GHz to IGHz as described above, the above-mentioned relationship of +, +lK1 leakage 1 to 2 1 to 2+1K2-1 to 3 holds true, and the Bragg condition between the guided light L1 and the surface acoustic wave 15 is satisfied. , the Bragg condition between the guided light L2 and the surface acoustic wave 16 is always satisfied.

As is clear from the above explanation, surface acoustic waves15.16
When the frequency of is 2 GHz and IGHz, the traveling directions of the guided wave L3 diffracted twice are the vector lk3 in FIG. 3 (1) and the direction of the vector lk3 in FIG. ), and the difference is 24-12-
It is 12°. In other words, a wide deflection angle range of 12'' is obtained by diffraction of the guided light twice by the surface acoustic waves 5 and 16.

After the frequencies of the surface acoustic waves 15 and 1B are changed continuously as described above, the generation of the second surface acoustic wave 1B is suppressed and only the first surface acoustic wave 15 is generated. The frequency changes continuously from 2 GHz to IGHz. Therefore, in this case, the surface acoustic wave 1
5 is 2 GHz, the deflection direction of the light beam L4 emitted from the optical waveguide 12 is the deflection direction of the guided light L2, which is the direction of the vector Ik2 in FIG. 3(1). This direction is the direction of ■゛ in Figure 3 (2), that is, the surface acoustic wave 1
This is the same as the deflection direction of the light beam L4 when both 5 and 16 are IGHz. When the frequency of the first surface acoustic wave 15 is continuously changed from this state to IGHz, the guided light L2 is continuously deflected as shown by arrow A in FIG. 1, and the frequency of the surface acoustic wave 15 changes. The deflection direction of the guided light L2 (that is, the deflection direction of the light beam L1) at IGHz is the direction of the vector Ik2 in (2) of FIG.

At this time, the deflection angle of the guided light L2 with respect to the guided light is δl
Then, δ m 6 a. In other words, due to the diffraction of the guided light L1 only by the first surface acoustic wave 15, δ1-6
A deflection angle range of ° is obtained. Therefore, the surface acoustic wave 1
Double diffraction of guided light by 5 and 16 and surface acoustic wave 1
By combining the one-time diffraction of the guided light only by 5, an extremely wide deflection angle range of 12+6-18 degrees is obtained in this device. By the way, the frequency is I
When optical beam deflection is performed using only one surface acoustic wave varying from GHz to 2 GHz (with a frequency band of one octave so as not to be influenced by second-order diffracted light), the deflection angle range is 6''.

Note that when the first surface acoustic wave 15 and the second surface acoustic wave 16 are traveling at a distance from each other, the optical path of the guided light L2 deflected only by the 2 GHz surface acoustic wave 15 is as shown in FIG. This is the position indicated by black square in , and is slightly shifted from the optical path of the guided light L3 deflected by the IGHz surface acoustic waves 15 and 16. However, this optical path deviation can be eliminated to the extent that there is no practical problem by making the travel paths of the first and second surface acoustic waves 15, tS as close as possible. Furthermore, by lowering the maximum frequency of the surface acoustic wave 15 during one-time diffraction slightly below 2 GHz while leaving the above deviation, the light beam scanning position on the scanned surface is the same as the one with the minimum deflection angle during second-time diffraction. It is also possible to adjust so that the light beam scanning position with the maximum deflection angle during one diffraction is adjacent to each other.

In addition, the deflection angle range obtained by diffraction only once, that is, the range from ■° to ■° in FIG. Although a small amount of unnecessary light is emitted, this unnecessary light does not pose any problem as long as this apparatus is used for optical scanning recording or reading of binary images, as described above.

In the above description, the frequency of the surface acoustic waves 15.16 is continuously changed from 2 GHz to IGHz, but on the contrary, it may be changed from IGHz to 2 GHz. In this case, only the direction of deflection of the light beam L4 is reversed. Also, change the above frequency to 2→1−
If the frequency is changed from 2 to IGHz, the light beam L4
is now deflected back and forth, making it possible to scan the light beam back and forth.

Furthermore, in the embodiment described above, the incident angle of the guided light L1 with respect to the surface acoustic wave 15 with a frequency of 2 GHz (that is, the angle formed by the electrode finger that excites 2 GHz of the first inclined finger chirp IDT 17 and the traveling direction of the guided light L1) is 6 degrees, and the angle between the electrode finger of the first inclined finger chirp IDT 17 that excites 1 GHz and the traveling direction of the guided light L1 is 3 degrees, and the electrode finger of the second inclined finger chirp IDT 18 that excites 2 GHz and IGHz. The angles it makes with the above direction of travel are each 181'
, 9°, but generally the minimum and maximum frequencies of surface acoustic waves 15.1B are fl Sr1 (f2-2fl)
In the above example, 6″, 3″, 18″
, 90 and the angles set as θ, θ/2.3θ, and 3, respectively.
If θ/2 is used, the above-mentioned Bragg condition can always be satisfied in any case. This will be obvious by referring to FIGS. 3(1) and 3(2).

Note that even when the shape of the inclined finger chirp IDT17.18 is defined by the above θ, the surface acoustic wave 15
．． 1B minimum and maximum frequency rl, f'2 as f2-2r,
It is not necessarily necessary to set the maximum frequency r2 to 21. You may set it slightly smaller than the value. However, as long as the inclined finger chirp IDT17.18 is formed in the shape described above, this IDT
Taking full advantage of the shape, the surface acoustic wave frequency between fl and [2-2f'1 is obtained so that the maximum deflection angle range can be obtained without the second-order diffracted light generated at the minimum frequency rl entering the deflection angle range. It is preferable to change the

Furthermore, in the present invention, the minimum and maximum frequencies flsf2 of the surface acoustic waves 15.1B are set to be f2-2fl, and the frequencies of the surface acoustic waves 15.16 are always changed so that they are equal to each other. Although it is not necessary, even if the frequencies and traveling directions of the surface acoustic waves 15 and te are changed individually, the first and second inclined finger chirp IDT
17. Depending on the shape and arrangement of 18, it is possible to satisfy the above-mentioned relationship of kl + lK5 - to 2 + lK2 - to 3. Further, the minimum frequency of the first surface acoustic wave 15 when diffracted only once does not necessarily have to be set equal to the minimum frequency f1 of the first surface acoustic wave 15 when diffracted twice.

However, as in the above embodiment, surface acoustic waves 15.
By changing the frequencies of 16 in the same way, it becomes possible to drive two tilted finger chirp IDTs with a common driver.
This is convenient because only one expensive driver is required.

In addition, in the device of the present invention, instead of the inclined finger chirp IDT17. , the frequency and traveling direction of the second surface acoustic wave may be continuously changed. FIG. 4 shows an example of the arrangement of this curved finger chirp IDT. In this example, the first curved finger chirp IDT1
．． 17 and the second curved finger chirp IDT 118, the rightmost electrode finger portion in the figure is a surface acoustic wave 15.1 with a maximum frequency r2.
6, and the left end electrode finger portion is configured to generate a surface acoustic wave 15.16 (indicated by a broken line in the figure) with a minimum frequency r1. In this case as well, if "2-2"l is used, the incident angle of the guided light L1 with respect to the first surface acoustic wave 15 with the maximum frequency f2 is θ, and the electrode finger portion at the left end of the first curved finger chirp IDT 117 are at an angle of θ/2 with respect to the traveling direction of the guided light Ll, while the right and left end electrode finger portions of the second curved finger chirp IDT18 are at an angle of 3θ and 3θ/2 with respect to the traveling direction of the guided light L1, respectively. 2
Both IDTs 117 and 118 may be created and arranged so as to form an angle of .

Further, when the optical waveguide 12 is replaced with the above-mentioned T1 diffusion LINbO3 and is made of ZnO, for example, the maximum and minimum frequencies of the surface acoustic waves 15 and 16 are set to 1. O.G.
Hz, 0.5 GHz, a deflection angle range of about Δδ-12° is obtained.

Furthermore, in order to make the light beam enter the optical waveguide 12 and emit it to the outside, the above-mentioned FGC 13,
In addition to 14, a coupler prism or the like may be used, or a light beam may be made to enter and exit directly from the end face of the optical waveguide 12. Further, in order to convert the diverging light beam L into a parallel beam or to focus the light beam L4 emitted from the optical waveguide 12, a waveguide lens or a normal external lens can be used.

(Effects of the Invention) As explained in detail above, in the optical deflection device of the present invention, a light beam that has been diffracted once by a surface acoustic wave is further diffracted by another surface acoustic wave, and a light beam that has been diffracted once by a surface acoustic wave is further diffracted by another surface acoustic wave. Since diffraction and single diffraction are combined, an extremely wide deflection angle range can be obtained. Therefore, by using the optical deflection device of the present invention, it is possible to shorten the distance from the optical deflection device to the surface to be scanned, thereby achieving miniaturization of the optical scanning recording device and the reading device.

In the device of the present invention, a wide deflection angle range can be obtained as described above without setting the frequency of each surface acoustic wave extremely high, so when using an IDT as a surface acoustic wave generating means, There is no need to set the line width extremely small, and this IDT can be easily manufactured using currently established technology. Further, as described above, there is no need to set the frequency of the alternating voltage applied to the IDT to be extremely high, and therefore the driver of the IDT can be easily and inexpensively formed.

[Brief explanation of the drawing]

Fig. 1 is a schematic perspective view showing an embodiment of the device of the present invention, Fig. 2 is a plan view showing an enlarged part of the above-mentioned embodiment device, and Fig. 3 explains the mechanism of light beam deflection in the present invention. FIG. 4 is a plan view showing another example of the surface acoustic wave generating means used in the present invention. 10... Light deflection device 11... Substrate 12.
...Optical waveguide 13...FGC for light beam incidence
14... FCC for light beam emission 15... First surface acoustic wave 16... Second surface acoustic wave 17... First inclined finger chirp IDT 18...
Second slope finger chirp IDT19...high frequency amplifier
20...Sweeper 21...Light source 117...First curved finger chirp IDT118...
Second curved finger chirp IDTL! ... Guided light L2 before entering the first surface acoustic wave... Guided light L3 that has passed through the first surface acoustic wave... Guided light that has passed through the second surface acoustic wave 1...・Wave number vector Ik2 of the guided light...wave number vector 1 of the guided light L2...wave number vector IK of the guided light L3...wave number vector IK2 of the first surface acoustic wave...second Wave number vector of surface acoustic wave Figure 1 Figure 2 Figure 3

Claims (6)

[Claims] (1) An optical waveguide formed of a material through which surface acoustic waves can propagate, and a first surface elastic member that propagates in a direction intersecting the optical path of the guided light traveling within the optical waveguide and diffracts and deflects the guided light. a first surface acoustic wave generating means for generating a wave in the optical waveguide; diffracting the guided light in a direction that travels in a direction intersecting the optical path of the diffracted guided light and further amplifies the deflection due to the diffraction; second surface acoustic wave generating means for generating a second surface acoustic wave to be deflected in the optical waveguide, and the first and second surface acoustic wave generating means
The wave number vectors of the guided light before and after being diffracted by the second surface acoustic wave are respectively |k_1 and |k_2, and the wave number vector of the guided light diffracted by the second surface acoustic wave |k_3
, the wave number vectors of the first and second surface acoustic waves are |K_1,
|K_2, the deflection angle of the guided light by the first and second surface acoustic waves is δ_2 to δ_3 (δ_2<δ_
In the range of 3), it operates to continuously change the frequency and traveling direction of the first and second surface acoustic waves, respectively, while satisfying the following conditions: |k_1+|K_1=|k_2 |k_2+|K_2=|k_3 , and in a range where the deflection angle is smaller than δ_2, the second surface acoustic wave generating means stops operating;
An optical deflection device, wherein the first surface acoustic wave generating means operates to continuously deflect the guided light within a deflection angle range of δ_1 to δ_2 (δ_1<δ_2). (2) The first and second surface acoustic wave generating means each include a pair of inclined-finger chirped interdigitated electrodes in which the electrode finger spacing changes stepwise and the direction of each electrode finger changes stepwise; 2. The optical deflection device according to claim 1, further comprising a driver that applies an alternating voltage whose frequency changes continuously to the electrode pair. (3) The first and second surface acoustic wave generating means each include a curved-finger chirped interdigitated electrode pair in which the electrode finger spacing changes stepwise and each electrode finger has an arc shape; 2. The optical deflection device according to claim 1, further comprising a driver that applies an alternating voltage whose frequency changes continuously. (4) When the deflection angle of the guided light is in the range of δ_2 to δ_3, the first and second surface acoustic wave generating means both take the same value between frequencies f_1 and f_2 (f_2≒2f_1), and the frequency increases. The guided light L_ is configured to generate a varying surface acoustic wave and is incident on the first surface acoustic wave having a frequency f_2.
1, the chirped interdigitated electrode pair constituting the first surface acoustic wave generating means has a frequency f_
1, the electrode fingers of the first surface acoustic wave generating portion form an angle of θ/2 with respect to the traveling direction of the guided light L_1, and the chirped crossed comb shape constitutes the second surface acoustic wave generating means. The electrode pair is formed such that the electrode fingers of the portions that generate surface acoustic waves of frequencies f_2 and f_1 form angles of 3θ and 3θ/2 with respect to the traveling direction of the guided light L_1, respectively, and the electrode fingers are formed on the first surface. When the second surface acoustic wave generating means is inactive, the elastic wave generating means generates a frequency f_0 to f_2 (
4. The optical deflection device according to claim 2, wherein the optical deflection device is formed to generate a surface acoustic wave whose frequency changes between f_0<f_2. (5) The optical deflection device according to claim 4, wherein the frequency f_0=f_1. (6) Optical deflection according to claim 5, wherein each pair of chirped interdigitated electrodes constituting the first and second surface acoustic wave generating means is driven by a common driver. Device.