Silicon Wafer: a Direct Output Coupler in Tm:YLF Laser**Supported by the Science and Technology Project of Shenzhen under Grant Nos JCYJ20140509172609175 and JSGG20140519104809878, and the Science and Technology Project of Guangdong Province under Grant No 2014B010131006.

Abstract

We present a high power diode-pumped continuous-wave Tm:YLF (Tm3+-doped lithium yttrium fluoride) laser with apiece of silicon wafer as the output coupler (Si-OC laser) directly. Under the pump power of 40 W at 793 nm, a maximum output power of 12.1 W is obtained with a beam quality of M2 ≤ 1.55 at 1887 nm, corresponding to an optical-to-optical efficiency of 30.25% and a slope efficiency of 33.21%. To the best of our knowledge, this is the first report on directly utilizing silicon as an output coupler (Si-OC) in the solid Tm:YLF laser system. Due to the intriguing characteristics of silicon, such as negligible absorption in the wavelength region around 2 μm, high damage threshold, low cost and long-pass filter properties, double-side polished monocrystalline silicon wafer is considered as an outstanding candidate output coupler in the high-power laser system 2 μm spectral region, which may dramatically reduce the total manufacturing costs of the 2 μm laser system.