Design of a double-pass shear mode acousto-optic modulator

Area of Science:

• Optics and Photonics
• Acousto-Optics
• UV Technology

Background:

• Acousto-optic modulators (AOMs) are crucial for light manipulation.
• High-power UV operation presents challenges due to material limitations and beam stability.
• Shear mode AOMs offer advantages but suffer from spectral leakage caused by strain-induced birefringence.

Purpose of the Study:

• To design and demonstrate a compact double-pass shear mode acousto-optic modulator for high-power UV operation.
• To eliminate beam deflection and angular changes during frequency tuning.
• To analyze and minimize spectral leakage caused by strain-induced birefringence.

Main Methods:

• A double-pass configuration with a spherical mirror retroreflector was employed to correct beam deflection.
• Analysis of strain-induced birefringence and beam polarization to mitigate spectral leakage.
• Heterodyne interferometry with two AOMs and offset acoustic frequencies was used to measure leakage intensity.

Main Results:

• The designed modulator achieved a peak double-pass efficiency of 42.6% at lambda=351.1 nm.
• A bandwidth of 28 MHz was demonstrated.
• Spectral leakage was reduced to a relative intensity of approximately 0.01%-0.04% over the operational bandwidth.

Conclusions:

• The developed double-pass shear mode AOM effectively addresses beam deflection and spectral leakage issues in UV applications.
• The design enables stable, high-efficiency modulation with minimal signal loss.
• This technology is suitable for demanding high-power UV optical systems.