DE2436536A1 - DEVICE FOR ACOUSTOOPTIC MODULATING OF LIGHT - Google Patents

Description

Device for acousto-optic modulation of light

The invention relates to a device for acousto-optic modulation of light, with a source of monochromatic light Light, with a block of acousto-optic material that is im Has spaced apart surfaces, of which © ine as an entry surface for the incident from the light source Light is provided, and the one more surface having? which is coupled to a piezoelectric transducer, the acoustic depending on suggested electrical signals Waves generated inside the acousto-optic material.

Α devices in which light and AKU ~ "STIC waves interact in such a manner ,, that a Liehtbündel is brought by bending in different positions _ .are already known and can be operated at continuously Attfzeiehnungs." - are brought playback or ÄfotastsYstemen application sur ». ^ - ■

In the known devices, different types of light = diffractors or deflectors are used, which work according to different physical »basic principles. The operational characteristics of such devices are typically characterized by the number of resolvable _g DAB Punkte.oder positions of the light beam divided by the diffraction angle CSesamfcabfcastwinkel DES ATAS treteadea frets Is J specified,. that the access time. Cdi © Since. _e al® is required to move the light spot or the lightbindel'iia to the next or another specific position and that the optical efficiency (the ratio between the optical power ia the light spot at the relevant position of the bundle rad the power of the incident light bundle). will »Such deflectors kösmera be mechanically acting, for example Vielfaeetteraspiegol ,? dl © are stored so that

They can be set in rotation at a relatively high speed, or galvanometer mirrors. Such deflectors can indeed move a light beam into a large number of positions within a relatively short time, but operational reliability is completely inadequate for practical use in high-resolution systems short scanning times, however, can only be inserted into an associated system at high cost. Galvanometers, in contrast, are relatively cheap, but they have an ice cycle time, see above. ά & Β such a deflector for άί & most Änwendungs'zwecka is too slow.

There are already devices of the type mentioned at the beginning with mechanical deflectors known. These. Devices _ satisfy, but also not fully. Acousto-optically 'arbeitend® devices of this type have namely dem'Machteil on ,, that if _f sie.ein have sufficient high resolution, the scan time is too long to be able to use these devices in fast-working image recording and Wiedergabesystemeri "So For example, a hoel-release device of this type has become known, which enables approximately IcSOG points of oäer Bünäelsteliurgen, but requires access for 64 microseconds. the * ΐτβηη they are laid out on a kiiiTse-Ipgriffsseit ;, they are sufficient at the same time offer a sufficiently high resolution more »So, for example, * _ is further? commercially available such devices; known in Oer although the access since only 10.6 MikrosekiaiidsR _s at the but the resolution is only about 775 points, "comes In these known devices aiisfc nor the disadvantage added that no sufficient ttnd constant diffraction efficiency over the entire waste 3, enk-bereioh is obtained ur> .d that these devices do not

optimal compromise between efficiency and resolution

As is known, light waves are diffracted by sound waves, thereby causing the light waves are deflected by a certain angle or at certain angle, depending on the frequency characteristic of the sound waves "" Depending on Änwendungsfall the sound waves may be amplitude-modulated or frequency-quenzrooduliert _o If the sound Wavefronts are sent towards di @ light = wavefronts in such a direction that the angle between the wavefronts fulfills the Bragg condition, then the propagating sound waves act SO; as if they were moving mirrors »Therefore, with a given frequency ratio, the angle of incidence and the diffraction of light behave as if it were an ordinary reflection relative positions of the light beam is made, the Bragg ⁵ see reflection condition in the known apparatus © »fulfill only over a limited sound frequency range, d _o h" only over a limited frequency range is obtained a usable Bragg ⁹ shear 'angle of reflection. It is also known - that in the known devices of this type, if they are to provide a good resolution, restrictions with regard to the scanning or deflection speeds possible here, the required frequency ranges and the highest possible opening

of the kind under discussion · to create those known to us such arrangements - a better compromise between accessibility and 'resolving power', i.e. a the highest possible resolution with very short access

In a device of the type mentioned, this object is achieved according to the invention in that the block of ak us toop ti apparent material is shaped so that it forms a step row with mutually parallel steps at one end, which are connected to each other via step surfaces, and that a separate converter is attached to each stage. Because several separate transducers are arranged in a stepped arrangement on the block of acousto-optical material, a composite sound wave front is generated during operation, which advances at such an angle to the light wave front that the Bragg ¹ see reflection condition can be fulfilled over a large bandwidth range.

As has been shown, this makes an extraordinarily high one Resolving power achieved with extremely short access time. In addition, there is an improved efficiency a large bandwidth, i.e. a large frequency range. aside from that larger deflection angles can be achieved compared to the known devices.

The device according to the invention enables a resolution of at least 1,500 points or positions of the bundle in one Diffraction efficiency of at least 10% over the entire bandwidth. The time-bandwidth product is 1,665. However, if a ramp-down time of 10% is used with linear scanning, the effective resolution is 1,500 Positions back. The device operates at a low power density and can also be operated at a high power level if the diffraction efficiency is increased should be achieved.

There is a need for such a device obvious, because such a device for image recording and / or playback systems of high resolution can be used, which is the case with the known devices of this type.

509808/0797

is not the case. As mentioned above, known devices of this type allow a resolution of approximately 775 positions of the light beam or less with a return time of 10 microseconds or more. With other people known device is achieved, although a resolution of 1600 points. However, there is a flyback time of 64 microseconds necessary. None of these known devices can be used in a high resolution recording or playback system Are used because here at least 1500 bundle positions with a return time of 14 microseconds or less must be given.

The block of acousto-optical material can be used in the inventive Device made of lead molybdate, on one side or surface of which a series of piezoelectric transducers is cemented. The acoustic waves that the transducers emit change the refractive index in the area of the opening of the block and bend some of the incident light at an angle

V '

where A is the wavelength of the incident light in a vacuum, f is the frequency of the acoustic wave and ν is the speed of the acoustic wave. In order to achieve operation over a large bandwidth, it is necessary to determine the direction of the acoustic propagation Wave, to be controlled in such a way that Bragg's condition at least, an-, This is achieved in the series of stages of the device according to the invention in that each stage has one has a certain step width and step height which correspond to the wavelength of the acoustic wave at the nominal frequency in Relationship, i.e. at the frequency for which the

50980870797

fende device is designed. As detailed below Will be explained in more detail, can be made by the special graduated arrangement of the transducers on the block of acousto-optical Material to provide a device applicable to high-speed, high-definition image recording and playback systems is.

As far as the terms "light" and "sound" are used here, these terms are intended to encompass light and sound in the broadest sense. In other words, “light” means both normal electromagnetic waves in the visible spectrum and electromagnetic radiation at wavelengths above or below the visible spectral range. "Sound" (and "acoustic") means any propagating physical or mechanical wave energy, not only that in the audible range, but also those vibrations that have frequencies such as those found in radio waves in the VHF range or VHF and / or UHF range are common. By "access time ^11" is meant the time that must elapse before a transmitted sound wave at the relevant frequency is fully effective in the acousto-optic material. The term "scanning time" refers to the time that elapses until the light beam covers an entire scanning line The term "flyback time" refers to the time it takes for the bundle to return to the home position from the end of the scanned line and this time can be considered to be equivalent to the access time.

509808/0797

The invention is explained in detail below with reference to the drawing nen explained. .:. ■; ·. ·.

Show it

Fig. 1 is a schematically drawn perspective View of an optical scanning system. with a light deflector;

; Fig. 2 shows a -: schematically drawn perspective - ' : see view of a preferred embodiment. example of an acousto-optic deflector;

Fig. 3 is a schematically drawn sketch of the

the deflector according to FIG. 2 associated elek-. ; ■ · tric circuit;

Fig; 4 and 5 enlarged and partly cut open and broken off; drawn top views

on the deflector according to FIG. 2 and "-: - .. ■■ ■■■■■■" .- 'S - ■' '· - ■ Fig. 6 a broken-off drawn top view

on the deflector provided with heat sinks.

In? 1 shows a typical optical system for one-dimensional scanning. In this optical system, a laser 10 is provided as a source for monochromatic light; Spherical lenses 11 and 12 pull the light bundle apart or collimate the bundle of the light emerging from the laser. A cylindrical lens 13 focuses the bundle in a line in the central area of a deflector designated as a whole by 14. The entire width of the opening of the deflector 14 is therefore used, but only a small one

509808/0797

Height (of the opening) required so that an increased efficiency is obtained for the beam diffraction, based on a given converter input power. A second cylindrical lens 15 is used to convert the bundle emerging from the deflector 14 back into a collimated bundle. This collimated light beam is then thrown through a lens 16 onto an image-receiving or information-receiving plane 17. In plane 17, S denotes the area of the positions of the beam or the extent of the deflection when the frequency is varied over the full frequency range. On the other hand, Z indicates the position of the undiffracted light beam of the zeroth order in the same plane. Such a system can be used as a recording or a playback system. In the first case, a photosensitive material, for example a photographic or electrophotographic material, can be arranged in the plane 17 and displaced in the x and / or y direction and in synchronism with the deflection movement of the deflected beam by means of a suitable device, so that a recording system is obtained . In the second case, a suitable visual display device can be arranged in the plane 17, for example a television screen, a display screen and the like. In the latter case, again depending on the intended use, further elements and / or electrical circuits may be required in order to obtain a complete system. The optical system shown above is insensitive to aberrations of the cylindrical lenses. Other possible optical systems, which may be of shorter length and have a different arrangement of lenses, prisms or mirrors, can also be used to achieve the same result. A more detailed description of the deflector itself is given below.

As can be seen from Fig. 2, the deflector 14 consists of a rectangular block 20 of acousto-optic material, each step 23 (Fig. 4) one on a side surface

509808/0797

■ - 9 -

24 formed step row 22 of the block 20 is a piezoelectric Converter 21 is cemented. The acoustic wave emitted from each of the transducers 21 causes a Change in the refractive index of the block 20 over the area of the opening depending on the number of steps 23.

Each of these acoustic waves diffracts part of the illuminating light by an angle ^θ = Α - ,, where Λ-

is the wavelength of the illuminating light in a vacuum, f is the frequency of the acoustic wave and ν is the speed of the mean acoustic wave. To get a work over a large bandwidth or a large frequency range is it is necessary to control the direction of propagation of the acoustic wave so that the Bragg condition approximates is satisfied. One method suitable for accomplishing this is shown in FIG. 2 and, in greater detail, in FIG 4 "and 5 shown.

With reference to FIGS. 2, 4 and 5, it should be noted that the series of steps 22 formed from the steps 23 is cut into the acousto-optic block 20. Each of the steps 23 has a width D and a height P_a_ / 2, where P is an integer greater than zero and ^ a. mean the wavelength of the acoustic wave at the nominal frequency f, ie the frequency for which the construction was designed. At frequencies that are greater or less than this frequency f _A , each of the transducers 21 emits a wave which is propagated perpendicular to the surface of the transducer. The result is a composite, stepped wave front, which corresponds in its effect to a single wave which advances at an angle. If the ratio of the width D to the height is chosen correctly, the Bragg's condition is approximately fulfilled by this angle of propagation, so that operation over an extended bandwidth or an enlarged frequency range is made possible. Even more important is the fact that, with a correct design of the series of stages, an operation over

509808/07 97

special frequency ranges is made possible with a greater total length L of the step series than would otherwise be possible.

The following results for the diffraction efficiency:

Π = sin

here is

χ = fT

² fe J—

L2nv ²

y = f L - ^ ~ 2 2nv

L ² PLP

(f - f) + 0.443 ^A

0.443

SIn (TTy) "y Nsin Ory / N) J

2 Λ 1/2

1 P ^(f - ^f A>

LfA ⁺ 2D ff,

In the above equations, f | the relationship between the optical performance in the diffracted bundle and the performance in the incident bundle.

M ₂ is the figure of merit of the acoustooptic material n ⁶ p ² / yv ³ , where f is the density and ρ is the photoelastic constant of the material. L is the total length of the row of steps, P is the effective acoustic power density in the deflecting medium. T is the width of each transducer, which is usually slightly smaller than the step width, n the refractive index of the acousto-optic medium, ν the speed of the acoustic wave, D the step width and P the integer indicating how many half-wavelengths the step height at the Frequency is f.

When setting up the above expressions, it was assumed that the angle of incidence of light is selected to be greater than the angle which results in an output maximum at the nominal frequency f. By choosing an angle that at f _{A is} 3 dB lower

509808/0797

the average 3dB bandwidth, by the factor Y? expand.

From the above equations it can also be shown that at a given bandwidth Δ £ = kf, where k rei the E in ze Ib at db te of the series of steps means that the greatest possible length of the series of steps results:

L = 7.1 nv ² / k ² f _A ² .

So that the largest 3 dB frequency of the individual elements is greater than is the upper 3 dB frequency of the step series, the following results for the parameter P:

P =

1 k <1.3

2 k <0.75

3 k <"0.5.

The following results for the number of levels:

N = 6.6 / Pk ²

The correct angle of incidence of light, measured outside the medium, is:

The effective acoustic power density P i is not equal to the electrical power supplied to the transducers 21, there some performance due to reflection due to electrical and mechanical impedance mismatch, due to scattering in the transducers, the electrodes and cement layers and in the acousto-optic Medium is lost in itself. These appearances were

509 808/0797

- 1 *) -

2 ^ 36536

calculated and taken into account in the overall design.

It is important that the illuminating beam the correct diameter and their correct position in the mouth of the deflector 14 aufweist- The effect of the acoustic attenuation in the deflecting medium causes the center of the Gaussian ¹ see the laser beam is moved against the transducer back and that as a result, the outgoing beam is no longer centered and the focused spot width is enlarged, which reduces the resolution. Although this shifting of the bundle has already become known, so far neither a teaching nor a suggestion has been made as to how this could be remedied. It should be noted that by intentionally moving the illuminating beam towards the row of transducers, diffraction efficiency can be increased at the expense of resolution and, more importantly, by moving the beam away from the row of transducers, resolution can be increased the efficiency can be improved. At a certain shift:

S _c / A = B (D / A) ² /69.5,

^s c ^the shift of the center,

where A is the width of the opening, / d is the diameter of the laser

Bundle with a radiation level of 1 / e and B the acoustic Attenuation over the area of the opening in decibels means the outgoing bundle is centered and the resolution corresponds that of a centered bundle without attenuation. It can be shown that for most purposes the optimal construction condition is D / A = 1, so that the diameter of the laser beam corresponds to the opening width and the following applies to the shift:

(S - Sc) A = 0.15,
where S is the displacement.

509808/0797

With such a choice of collar, oil diameter and displacement the resolution is only slightly worse than for the case without attenuation (the spatial frequency at which the normalized modulation transfer function has dropped to 1 / e, is approximately 95% of the value that is without attenuation and without displacement results), and the effect of damping the acoustic wave is P / 2 decibels. Such an interpretation can can be used up to values of the attenuation which amount to 2OdB over the area of the opening; beyond such attenuation values begins the. Resolution to fall off.

Reference is now again made to FIGS. 2 to 5. The deflector 14 is preferably made from lead molybdate. This material is currently the most important and most useful of those in recent years for acousto-optic use in materials developed in the visible light range. This stuff

- 18

has a high figure of merit IL · = 35.8 χ 10 cgs units, has a high transparency in the visible range, a low one

acoustic attenuation (11 dB / cm-GHz) and is not soluble in water.

Other substances with higher M_ values are known. Lead molybdate, however, from eq ^en these materials, they are readily available in good optical quality für.eine using visible light, the most satisfactory material. The block 20 is cut to size and its entry surface 25 and its exit surface 26 are optically polished. The axes of the block 20 per se can be arranged in a variety of ways. In this case, when the longitudinal acoustic wave propagates in the c-axis direction as shown in Fig. 2, the optical wave travels along the b-axis and polarizes along the a-axis, or the optical wave travels along the C-axis and polarized along the b-axis. In the latter cases the figure of merit is

- ι ft
smaller, M ₂ = 24 χ 10. cgs units. This cut results

Although it is less efficient, it can be manufactured more easily because the crystal is normal to the c-axis having running cleavage plane.

509808/0797

2 ^ 36536

The steps 23 are cut into the side surface 24 of the block 20 which is finely ground at the opposite end 27 and on its upper and lower surfaces 28 and 29, respectively. An acousto-optical absorber 30 made of lead, aluminum or an epoxy resin, which is provided with tungsten powder in order to achieve an acoustic impedance which is substantially the same as that of the lead molybdate, is cemented to the end 27. The absorber 30 is used to prevent the acoustic waves generated inside the block 20 by the transducers 21 from being reflected. Panels 31 and 32 of aluminum or copper are cemented to the top and bottom surfaces 28 and 29, respectively, by means of an epoxy resin or other adhesive. These plates 31 and 32 serve as heat sinks and can also serve to support the deflector 14 or, together with plates 33 and 34, can also serve to arrange the deflector 14, as shown in FIG. 2, in an insulated manner in the associated system, if necessary. In the latter case the plates 33 and 34 would be made of insulating material.

Each of the steps of the step series 22 is provided with a transducer 21 which is designed in the form of a rectangular plate and preferably consists of lithium niobate, a known transducer material which is easily available in good quality. This transducer material has a high electromechanical coupling factor (0.49) when cut as a 35 Y-cut and has an acoustic impedance that is well matched to that of lead molybdate (34.8 and 26, respectively). Lithium niobate also has a low dielectric constant (39).

With each stage 23 of the series of stages 22 is a converter 21 by means an adhesive layer 35 made of indium cemented. Bonding techniques using indium are known. The usage of indium or some other metallic adhesive is required to have a good impedance match as well

509808/0797

a good acoustic transmission - to get. However would the high acoustic damping of indium, you wouldn't compensate, degrade the diffraction efficiency of the system at high frequencies unacceptably. In addition, the Open-air resonance frequency of a converter to a lower one Decreased value when the converter is using a different medium is cemented. For these reasons, the transducers 21 are thinner cut / as it is for a resonance at the nominal frequency of the Deflector 14 is required. By doing this the sensitivity of the transducer 21 by about 30% in the direction of higher frequencies can be shifted towards higher frequencies Frequencies given higher sensitivity are used to increase the attenuation of the adhesive layer 35 made of indium to compensate. This creates a flatter curve of the overall sensitivity related to the deflection efficiency obtain.- : ' -.··.·-

The numeric parameters of a. .Example of an Deflectors of the type described above are the following:

Lead molybdate: M- = '36 χ 10 cgs units (acoustic propagation ■ - ■■ - ■ · ■■■■ - ■ -, 'direction of planting along the

- "'c-axis) V' · - '3 " f 75 mm / t (.s ·

η = 2.27 at a wavelength of 0.64 ^ m.

Row of transducers; · f ^ = 175 MHz
'' L = 1.81 cm

N = 6 converters
P = 2

Af = 125 MHz

2
P, = 0.5 w / cm

5 0 9 8 0 8/0797

Transducer: strength 15.6 <i.m (resonance frequency 236 MHz) Adhesive: indium, 5 <<. M or less thick. Optical efficiency: 10% or more over the full bandwidth, 25% at the apex.

The associated electrical circuit and the connections between the transducers are shown in Figs. As a voltage source, which have a predetermined frequency range available represents, an oscillator 36 can be provided to which a transformer 37 is assigned, which is shown schematically in FIG. 3 is indicated, so that an oscillator unit designated as a whole by 38 is formed. The transducers 21 are through Lines 40 connected in series with the oscillator unit 38. The lines 40 are, as shown in Fig. 4, alternate arranged on step surfaces 39. The lines 40 connect the adhesive layers 35 made of indium, which the transducers 21 cement with the respectively assigned level 2 3. Alternatively, however, the transducers 21 can also be connected to one another in this way be that, as shown in Fig. 5, the surfaces 28 and

29 of the block 20 are coated with connecting layers 41, which are formed as thin film layers rather than a compound to be provided along the step surfaces (as shown in FIG. 4 using the example of the lines 40). If the latter alternative Solution is used, the plates 31 and 32 serving as heat sinks are cut short in such a way that that the connecting layers 41 remain free and thereby the adhesive layers 35 are not short-circuited with one another can. The transducers 21 are polarized in opposite directions and radiate in phase, although they are connected in series. Therefore changes the direction of the electric field. The transformer 37 matches the impedance of the transducer 21 to that of the Oscillator unit 38 or the power source and transmission lines at. Part of the transformer acts as an inductance, to the static capacity of the transducer 21 in the

50 9 8 08/0797

To neutralize the nominal frequency f of the same.

In Fig. 6 the external electrical connections are shown, which are designed to form heat sinks in conjunction with the acousto-optic deflector 14. With this arrangement is a block 45 of insulating material near the side surface 2 4 of the block 20 in a suitable manner with the plates 31, 32 or 33, 34 connected. The block 45 of insulating material carries a number of rods 46 and 50, from each of which is feathered at one end 47 and touches an associated transducer 21 with its other end 48, if the block 45 is attached to the side surface 24. The rods can be made of aluminum, copper or brass, a rectangular one or round cross-section and are blackened so that they have good radiation. Such bars or Feathered elements can also be attached to other surfaces of the deflector 14 if they are only used as heat sinks Apply, except for the entry surface and the exit surface. 25 or 26. ',

As can be seen from FIGS. 3 and 6, the bars 46 are connected to the transformer 37 via lines 51 and 52. The rods 50 also serve as they form contiguous pieces with two spaced apart ends 48a as connecting lines, the adjacent transducers 21 to each other associate. The rods therefore serve both to connect the transducers 21 in series and as heat sinks.

In operation, the laser 10 produces a small monochromatic beam Light that passes through the optical system of the lenses ^ 11, 12 and 13 as a narrow slit of light within the deflector is focused. In fact, the bundle is focused in the center or in the median plane of the deflector 14. «, Die

The oscillator unit 38 is connected in series with each of the converters 21 via the transformer 37. At the predetermined acoustic frequency f, each transducer emits a wave of the corresponding frequency from the side surface 2 4 towards the opposite end 27. The series of waves radiated from each transducer 21 is out of phase. A composite wavefront is therefore generated by the step series 22 of the transducers. The included angle between this composite wavefront and the incident light changes with the frequency f in such a way that the Bragg ¹ see condition is maintained over the frequency range Λ f of the deflector. When the frequency is changed over the entire frequency range, the wavefront shifts and the included angle changes, so that the exiting light moves through an angle which can be used for recording or scanning purposes. As described above, this angle results in at least 1500 different positions of the bundle.

The device described here is used to deflect a monochromatic light beam of a laser in at least 1500 resolvable layers with a return time of 13.3h see, with a diffraction efficiency over the full frequency range or the entire range of at least 10% guaranteed is. The time-bandwidth product is 1665. When used for linear scanning with a flyback time however, from 10% the effective resolution is reduced to 1500 bundle layers or points. The facility works with

a low power density of 0.5 w / cm. With good training the heat sinks can be operated at high power levels to achieve higher diffraction efficiency receive. The overall weighing shown, in which one intentionally off-center lighting g with a suitable bundle Form is made in order to find an optimal compromise

509808/0797

to obtain from resolving power and efficiency, is novel compared to the teachings conveyed by the prior art. Also the use of high frequency converters, that can process a higher frequency * than the the nominal frequency of the construction design Device, results in a compensation of the attenuation in the individual adhesive layers, which are necessary for to hold the acousto-optic element together.

50980 8/0797

Claims (1)

- 20 claims [1.J Device for acousto-optic modulation of light / with a source for monochromatic light, with a block of acousto-optic material which has surfaces running at a distance from one another, one of which is provided as an entry surface for the light incident from the light source, and which has a further surface which is coupled to a piezoelectric transducer which, in response to supplied electrical signals, generates acoustic waves inside the acousto-optic material, characterized in that the block (20) of acousto-optic material is shaped to be at one end a row of steps (22) with mutually parallel steps (23) which are connected to one another via step surfaces (39), and that a separate transducer ( ²¹ ) is attached to each step (23). 2. Device according to claim 1, characterized in that the transformer (2X) is formed substantially rectangular in shape and are cemented to the interconnected via the step faces (39) surfaces of the steps (23) and that the transducer (21) electrically connected in series and connected to an electrical oscillator unit (38), so that the transducers (21) emit acoustic waves in phase to form a composite wave front. 3. Apparatus according to claim 2, characterized in that the surfaces connected to one another via the step surfaces (39) of the stages (2 3) essentially. perpendicular to the Step surfaces (39) run. _ .4. Device according to one of Claims 1 to 3, characterized in that that at the end of the row of steps (22) opposite (27) of the block (20) an absorber (30) for absorbing and dispersing those which have passed through the block (20) acoustic waves is provided. 5. Apparatus according to claim 4, characterized in that the absorber (30) has essentially the same acoustic Has impedance like the acousto-optic material of the Blocks (20) .. 6. Device according to one of claims 1 to 5, characterized in that that, entry surface (25) and exit surface (26) except on at least one surface of the Blocks (20) a heat sink (31, 32, 46, 50) for the removal of generated by the propagation of acoustic waves Heat is provided. ■ 7. Device according to one of claims 1 to 6, characterized in that that the acousto-optic block (20) is mounted in material on a support (31 to 34). 8. Device according to one of claims 1 to 7, characterized in that that one with the light source (10) cooperating optical device is provided, which is a first cylindrical lens (13) for focusing the light in a narrow straight line within the acousto-optic material and a second cylindrical lens (15) to recirculate the light emerging from the acousto-optic material to spread a wider beam of light. 9. Device according to one of claims 1 to 8, characterized in that that the light beam of the light source (10) relative to the entrance surface (25) of the block (20) opposite the centered Position is shifted to improve the efficiency and resolution of the acousto-optic material, and that the beam . on the entry surface (25) at such an angle. falls that the Bragg ¹ see condition is met. 509808/0797 10. Device according to one of claims 1 to 9, characterized in that that lead molybdate is provided as acousto-optical material and that the transducer (21) is made of lithium niobate are made. 11. The device according to claim 10, characterized in that the thickness of the lithium niobate of the transducer (21) is approximately IS ₁ Gt ^ m and that the lithium niobate by means of a layer of indium, the thickness of which is not more than 5 ^ m, with the acousto-optical Material is cemented. 12. Device according to one of claims 1 to 11, characterized in that that the resonance frequency of the transducer (21) is higher than a predetermined nominal frequency of the device. 13i device according to claim 12, characterized in that the height of the steps (2 3) with the nominal frequency expressed in half wavelengths in an integer Relationship stands. 14. Device according to one of claims 1 to 13, characterized in that that the series of steps (22 ^ six steps (23) having. . 15. Device according to one of claims 1 to 14, characterized in that that at a predetermined nominal frequency of the device on the order of about 175 megahertz the resonance frequency of a piezoelectric transducer approximately 236 megahertz. 509808/0797