Power scaling of narrow-linewidth 2μm GaSb-based semiconductor disk laser

Abstract

Summary form only given. In recent years, optically pumped semiconductor disk lasers (SDLs) have attracted considerable interest, since they deliver simultaneously high output power and excellent beam quality. Recently, the realization of high-performance SDLs based on the (AlGaIn)(AsSb) material system with emission wavelengths ranging from 1.8 to 2.8 μm has been reported. Room-temperature output powers of up to 4.2 W have been demonstrated recently, making this laser source interesting for direct applications such as medical therapy or materials processing. Further applications in this wavelength regime such as high-resolution spectroscopy, long-range gas sensing, LIDAR and free-space optical data transmission via phase modulation require single-mode narrow-linewidth (kHz range) emission and output powers in the 0.1-1 W range. Higher output powers are a clear benefit since, e.g. in data transmission, fewer, or even no subsequent power amplifier stages will be required. A typical benchmark for amplifier-free airborne communications is 1 W at <;100 kHz linewidth. In this contribution we will present a 2-μm semiconductor disk laser that emits in free-running operation an output power of 1 W cw at a linewidth of 60 kHz, which is a ten-fold power increase compared to our previous reports and outperforms any other 2-μm kHz-linewidth laser demonstrated so far by a factor of 40 in output power. Using Pound-Drever Hall (PDH) stabilization significant improvements of the wavelength stability could be obtained where beat-note spectra for free-running and PDH-stabilized operation recorded at 1 W output power during a sampling time of 100 μs are shown. For further power scaling, we used an improved cavity setup, which allows larger on-chip mode diameters. This way we could demonstrate that 2 μm SDL are capable of delivering even more than 2 W cw in single-frequency operation at narrow linewidths below 2 MHz. The limitations for further power scaling of this single-frequency laser and possible solutions will be discussed in detail.