A research team led by Dr. ZHANG Tianshu at the Anhui Institute of Optics and Fine Mechanics, the Hefei Institutes of Physical Science of the Chinese Academy of Sciences, has successfully developed a fiber–solid hybrid single-frequency Innoslab amplification system that boosts single-pulse energy from the microjoule level to 1.8 mJ while maintaining excellent beam quality and polarization.
This achievement, published in Optics Express, provides a powerful new solution for high-performance pump sources used in OHx radical detection.
Detection of OHx radicals requires a single-frequency 308 nm laser, typically generated through optical parametric amplification (OPA). However, current OPA pump sources struggle with multiple limitations, including power loss in continuous-wave seed sources after pulse modulation, nonlinear effects and low damage thresholds in all-fiber amplifiers, limited small-signal gain in traditional solid-state amplifiers, and bulky multi-stage architectures. These issues prevent the realization of compact, high–single-pulse-energy pump sources.
To solve this, the team developed a fiber–solid hybrid architecture integrated with Innoslab beam-combining amplification, enabling the conversion of a single-frequency continuous-wave seed laser into a millijoule-level single-frequency pulsed laser. In the setup, the seed laser is coupled into a polarization-maintaining fiber via a half-wave plate and fiber coupler, modulated into pulses by an Electro-Optic Modulator, and then amplified through a two-stage fiber amplifier. The output is collimated and injected into an Innoslab amplifier to boost the small-signal pulse to high energy.
Experiments showed that the system preserves high horizontal beam quality while enhancing vertical beam quality, indicating an optimized optical design. The amplified laser maintains a polarization extinction ratio of about 30 dB, and the Innoslab amplifier increases pulse energy from 5 μJ to 1.8 mJ in a single stage, reflecting excellent gain performance. The system also demonstrated the ability to amplify nJ-level single-frequency pulses to the μJ range, offering a promising approach for amplifying extremely weak solid-state laser signals.
The results provide a key enabling technology for advanced environmental-monitoring instruments, supporting applications in air pollution analysis, greenhouse gas detection, and broader research on atmospheric protection and climate change.
Schematic of the Innoslab fiber solid hybrid amplifier (Image by ZHANG Tianshu)
Three-dimensional thermal effect simulation of laser crystal (Image by ZHANG Tianshu)