Wide bandgap photoconductor (SiC:V)-based optically addressed light valve for high fluence operation

Area of Science:

• Optoelectronics
• Materials Science
• Semiconductor Devices

Background:

• Optically Addressable Light Valves (OALVs) are crucial for optical modulation.
• Existing Bismuth Silicon Oxide (BSO) based OALVs have limitations in laser-induced damage threshold.
• Wide bandgap semiconductors offer potential for improved device performance under high laser fluences.

Purpose of the Study:

• To design and fabricate optically addressable light valves using wide bandgap 4H- and 6H-Silicon Carbide (SiC) as photoconductors.
• To enhance the operational laser fluence tolerance compared to state-of-the-art BSO-based devices.
• To characterize the photoresponsivity and laser-induced damage threshold of SiC-based photoconductors.

Main Methods:

• Vanadium-doped 4H- and 6H-SiC were selected as photoconductive materials.
• Laser-induced damage threshold was measured using a Nd:YAG laser (1064 nm) at ~200 sites per sample.
• Photoconductive switches were characterized for photoresponsivity at 380, 405, and 447 nm.
• Devices were fabricated by bonding SiC to BK7 glass with microsphere spacers and filling with liquid crystal.
• Device modulation and transmission were tested using address beams at specific wavelengths.

Main Results:

• SiC samples exhibited significantly higher laser-induced damage thresholds (1.75 J/cm² for 4H-SiC, 1.8 J/cm² for 6H-SiC) compared to BSO (0.4 J/cm²).
• Peak photoresponsivity was observed under 380 nm for 4H-SiC and 405 nm for 6H-SiC.
• Fabricated OALVs achieved >90% transmission with a sinusoidal voltage waveform, meeting device lifetime requirements.

Conclusions:

• Wide bandgap 4H- and 6H-SiC are promising photoconductors for optically addressable light valves requiring high laser fluence tolerance.
• SiC-based OALVs demonstrate superior laser damage resistance and effective optical modulation capabilities.
• The developed SiC/LC devices meet performance and lifetime criteria for advanced optical applications.