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Ultraviolet acoustooptic device and optical imaging device

Inactive Publication Date: 2005-06-02
PANASONIC CORP
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] Hence, the present invention provides an acoustooptic device in which no laser damage nor optical damage is caused, and is intended to provide an ultraviolet acoustooptic device and optical imaging apparatus using the same that require low driving power, allow heat to dissipate well, and thus do not necessarily require water-cooling.

Problems solved by technology

Furthermore, the acoustooptic device in which quartz glass, a quartz crystal, or a KDP crystal is used delivers poor acoustooptic performance, requires a large radio-frequency power source for driving the device, and has to be water-cooled to control the heat generated therein.
In the acoustooptic device in which the KDP crystal is used, it is difficult to have a moisture resistant structure since the KDP crystal is a water-soluble crystal.
Moreover, since the quartz crystal is a hard crystal, it takes a considerable time for processing it when it is used as an acoustooptic medium.
It has been conceived that the acoustooptic device in which a LN crystal is used is not suitable as an acoustooptic device that handles light with a short wavelength due to optical damage and laser damage caused therein.
As a result, a considerably deteriorated beam shape is observed because of the Pockels effect.
In an optical imaging apparatus using a conventional ultraviolet acoustooptic device, there have been problems in that its acoustooptic medium has to be provided with moisture resistance, heat has to be dissipated by water-cooling, and a large driving circuit is required.

Method used

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  • Ultraviolet acoustooptic device and optical imaging device

Examples

Experimental program
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Effect test

example 1

[0058] In order to examine laser damage and optical damage caused by ultraviolet light, various kinds of single crystal materials were evaluated with respect to their light resistance using a laser having a light source of third harmonics of a YAG laser. The result is shown in Table 1. The crystal materials evaluated herein were a TeO2 crystal that had been used conventionally, and LN, MgO:LN, Li2B4O7, (GdY)1Ca4O(BO3)3, and CsLiB6O10 that were used for the acoustooptic device of the present invention.

TABLE 1Absolute ValuePresence orof Laser DamageRelative ValueAbsence ofThresholdof Laser DamageOpticalMaterial(kW / mm2)ThresholdDamageTeO2291AbsentLN873PresentMgO:LN57-872-3AbsentLi2B4O7At least 120At least 4Absent(GdY)1Ga4O(BO3)3At least 120At least 4AbsentCsLiB6O10At least 120At least 4Absent

[0059] From the result, it is understood that among these materials, the TeO2 crystal has the lowest relative value of the laser damage threshold and therefore is the most susceptible to the lase...

example 2

[0066] Acoustooptic devices like the one shown in FIG. 1 were produced and their acoustooptic performance was evaluated as in Example 1 using a GaN-based LED that emitted light having a wavelength in the range of 360 nm to 380 nm. The LED used herein had a maximum output of about 2 mW.

[0067] In this case, the diffraction efficiency was about 4% to 15% as shown in Table 3, with the input power of an RF signal being 2 W. The reason why the diffraction efficiency decreased as compared to that in Example 1 conceivably is that the wavelength of the incident light was slightly longer and the monochromaticity of the light source was poorer. When using the incident light having power in this range, no optical damage was found even in the case of using a common LN single crystal.

TABLE 3DiffractionMaterialEfficiency (%)LN15MgO:LN15Li2B4O74(GdY)1Ga4O(BO3)35CsLiB6O104

example 3

[0068] Acoustooptic devices like the one shown in FIG. 1 were produced and their acoustooptic performance was evaluated with respect to fourth harmonics of a YAG laser having a wavelength of 266 nm. In this case, it was not possible to use LN and MgO:LN for the acoustooptic devices since they do not transmit ultraviolet light having a wavelength of 266 nm. The diffraction efficiency of the acoustooptic devices produced using the Li2B4O7 crystal, the (GdY)1Ca4O(BO3)3 crystal, and the CsLiB6O10 crystal was 6% to 8% as shown in Table 4. In addition, deteriorations in transmittance and beam pattern were not found even after these acoustooptic devices were irradiated with ultraviolet light having a wavelength of 266 nm for 10 hours continuously.

TABLE 4DiffractionMaterialEfficiency (%)LN—MgO:LN—Li2B4O76(GdY)1Ga4O(BO3)38CsLiB6O107

[0069] With respect to the (GdY)1Ca4O(BO3)3 crystal, in the case of using light having a wavelength of 266 nm, higher light transmittance was obtained when YCa4...

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Abstract

The present invention provides an ultraviolet acoustooptic device including: a radio-frequency signal input part; a transducer unit for converting a radio-frequency signal into a mechanical vibration; and an acoustooptic medium whose optical characteristic varies according to the mechanical vibration. In the ultraviolet acoustooptic device, light entering the acoustooptic medium is ultraviolet light having a wavelength of 380 nm or shorter, and the acoustooptic medium is formed of an oxide single crystal containing at least boron as a component of its unit cell, a LiNbO3 crystal, or a LiNbO3 crystal doped with MgO. Thus, an acoustooptic device can be obtained in which no laser damage nor optical damage is caused, and an ultraviolet acoustooptic device and an optical imaging apparatus using the same can be provided that do not necessarily require to be water-cooled.

Description

BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] The present invention relates generally to acoustooptic devices such as acoustooptic modulators, acoustooptic deflectors, acoustooptic filters, acoustooptic frequency shifters, etc. Particularly, the present invention relates to ultraviolet acoustooptic devices, such as acoustooptic modulators, acoustooptic deflectors, acoustooptic filters, acoustooptic frequency shifters, etc. that utilize ultraviolet light with a wavelength of 380 nm or shorter, and to optical imaging apparatuses using the same. [0003] 2. Related Background Art [0004] Conventionally, a TeO2 crystal or a PbMoO4 crystal has been used for acoustooptic media for visible light emitted from an argon laser or a helium-neon laser. On the other hand, recently, it has been studied to combine an acoustooptic device with various types of ultraviolet sources that emit lights with shorter wavelengths, i.e. ultraviolet light, such as, for example, a YAG laser em...

Claims

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Application Information

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IPC IPC(8): G02F1/00G02F1/33
CPCG02F1/33G02F1/0009
Inventor MINEMOTO, HISASHINISHIYAMA, TOSHIMISHIBUYA, KIMIHIKO
Owner PANASONIC CORP
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