Increasing the output energy of MID-IR laser system for muounic-hydrogen spectroscopy

In this paper we describe a promising approach to increase the output energy of a laser system emitting infrared radiation in the spectral range 6.78μm based on direct difference frequency generation in non-oxide nonlinear crystals using single-mode Nd:YAG laser and tunable Cr:forsterite laser, which was developed for the muonic-hydrogen experiment. The investigated system is based on lithium thioindate (LiInS₂) crystal cut for type II difference frequency generation. The pulses of the Nd:YAG laser (1,064 μm) are combined with the pulses at ~ 1.262 μm of the Cr:forsterite laser through a dichroic mirror and sent to the nonlinear crystals in different optical geometries. The generated radiation reaches an output energy more than 90 μJ in a single pass optical geometry, has 10 ns long pulses at 50 Hz frequency repetition rate and is tunable in the range 6695 - 6870 nm. These results prove the suitability of such an approach for building the laser system for the muonic-hydrogen experiment.