Continuously Pumped All-Solid-State Laser Systems with Fiber Phase Conjugate Mirror

摘要

All-solid-state laser sources are required for numerous applications in industry and science. Scaling of average output power while preserving a diffraction limited beam quality results in high brightness operation. However, conventional laser systems suffer from thermally induced phase distortions in the active medium, which considerably reduce their beam quality. Advanced pumping geometry, diode pumping, as well as active media with high quantum efficiency can reduce the thermal load. But the remaining phase distortions result in a reduction of beam quality. Optical phase conjugate mirrors are suitable to compensate for phase distortions in master oscillator power amplifier systems (MOPA). Stimulated Brillouin scattering in conventional, commercially available silica fibers facilitates reliable and stable phase conjugation. These all-solid state devices reveal an energy reflectivity of almost 90percent and require low financial efforts. Moreover, the SBS threshold is determined by the appropriate fiber core diameter. Therefore fiber phase conjugators can be applied in continuously pumped, repetitively q-switched laser systems which usually exhibit smaller peak power in comparison with pulsed pumped systems. A four-pass amplifier arrangement with birefringence compensation was developed. Nearly diffraction limited output with 32 W average power has been achieved at 10 kHz repetition rate. Power scaling up to 100 W seems to be possible.