Design and Performance Study of Two-Dimensional Acousto-Optic Q-Switch with New Geometric Structure

doi:10.16553/j.cnki.issn1000-985x.2025.0248

Abstract

Abstract: The two-dimensional acousto-optic Q-switch is a key component in laser Q-switching systems. Traditional devices based on a right-angle triangular prism geometry suffer from inherent drawbacks， including return acoustic wave interference， diffraction spot distortion， stepped distortion in the modulation waveform， and a complex three-sided water-cooling structure. This work proposes a new geometric structure for a two-dimensional acousto-optic Q-switch to fundamentally eliminate return acoustic wave interference， simplify thermal management， and achieve high diffraction efficiency with clean modulation waveforms， while maintaining compactness and reliability for high-power laser applications. In this paper， a fused silica acousto-optic crystal with a non-symmetrical wedge geometry was designed. Unlike the conventional right-angle prism， the new geometry structure ensured that after the first orthogonal acousto-optic interaction of the acoustic wave， the reflected acoustic paths were spatially offset from the main working region， thereby avoiding return wave interference. Two orthogonal y-36° LiNbO₃ transducers were bonded onto the crystal， with a center frequency of 27.12 MHz and an operating wavelength of 1 064 nm. The effective aperture is 3 mm×3 mm （rectangular） and the acousto-optic interaction length was 42 mm. The water-cooling structure was simplified from three-sided water-cooling structure to two main water-cooling blocks， reducing assembly complexity. Experimental results show that with dual-channel radio frequency （RF） drive power of 47 W per channel， the two-dimensional diffraction efficiency reaches 98.5%， and the diffraction spot pattern exhibits a regular grid distribution without distortion. The modulation waveform shows a steep rising edge （~307.7 ns） and falling edge （~774.8 ns） with a flat top， free from the stepped distortion observed in conventional devices. The impedance curve at 27.12 MHz is smooth and close to 50.2 Ω， matching standard RF systems. Thermal imaging reveals a steady-state crystal temperature of approximately 69.7 ℃ under dual-channel RF drive power of 47 W per channel （compared to 54.4 ℃ for the conventional design）， which is well below the softening point of fused silica. A 4 h continuous aging test confirms excellent thermal stability. The temperature stabilizes at （71±1） ℃， the diffraction efficiency remains between 97.5% and 98.7% （standard deviation ~0.28）， and the modulation waveform shows no degradation. In this paper， the proposed two-dimensional acousto-optic Q-switch with new geometric structure successfully eliminates return acoustic wave interference through spatial path control， providing a universal design approach applicable to other acousto-optic materials （e.g.， TeO₂， SiO₂， Ge） for different laser wavelengths. Although the new geometry structure imposes slightly higher precision requirements on crystal fabrication， the simplified two water-cooling block structure reduces overall assembly cost and complexity， while maintaining high performance and long-term reliability. This work offers a practical and innovative pathway for developing advanced acousto-optic devices.

Key words: two-dimensional acousto-optic Q-switch; geometric structure; acousto-optic crystal; transducer; fused silica; diffraction efficiency; waveform; return acoustic wave

CLC Number:

O734

XU Zhihong, ZHANG Xuefeng, WANG Chengqiang, WANG Shuaihua, WU Shaofan. Design and Performance Study of Two-Dimensional Acousto-Optic Q-Switch with New Geometric Structure[J]. Journal of Synthetic Crystals, 2026, 55(4): 584-593.

Figures/Tables 12

Fig.1 Structural diagram of traditional two-dimensional acousto-optic Q-switch （a） and schematic diagram of its diffraction spot （b）

Fig.2 Acoustic paths of traditional two-dimensional acousto-optic Q-switch. （a） Ideal situation；（b） failure caused by processing deviation；（c） failure caused by acoustic field side lobes

Fig.3 Actual anomalous phenomena of traditional two-dimensional acousto-optic Q-switch. （a） Diffraction spot when transducer 1 operates independently；（b） diffraction spot when transducer 2 operates independently；（c） stepped waveforms when working simultaneously

Fig.4 Acoustic path design of two-dimensional acousto-optic Q-switch with new geometric structure. （a） Main reflected path of acoustic wave propagation；（b） path considering acoustic divergence characteristics

Fig.5 Comparison diagram of mechanical structure of two-dimensional acousto-optic Q-switches. （a） Traditional structure；（b） new design

Fig.6 Thermal simulation comparison diagram of two-dimensional acousto-optic Q-switches. （a） Traditional structure；（b） new design

Fig.7 Physical photos of two-dimensional acousto-optic Q-switch with new geometric structure. （a） Acousto-optic crystal；（b） device

Fig.8 Diffraction efficiency curve and diffraction spot distribution of two-dimensional acousto-optic Q-switch with new geometric structure

Fig.9 Modulation waveforms of a two-dimensional acousto-optic Q-switch with new geometric structure

Fig.10 Impedance curve of two-dimensional acousto-optic Q-switch with new geometric structure

Fig.11 Temperature thermal imaging comparison diagram of two-dimensional acousto-optic Q-switches. （a） Traditional structure；（b） new design

Fig.12 Long-term stability test results of two-dimensional acousto-optic Q-switch with new geometric structure. （a） Crystal temperature and modulation waveform；（b） diffraction efficiency

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