Abstract
In this paper, we present a high-energy, narrow pulse-width, long-wave infrared laser based on a ZnGeP2 (ZGP) optical parametric oscillator (OPO). The pump source is a 2.1 μm three -stage Ho:YAG master oscillator power-amplifier (MOPA). At a repetition frequency of 1 kHz, the Ho:YAG MOPA system outputs the maximal average power of 52.1 W, which corresponds to the shortest pulse width of 14.40 ns. By using the Ho:YAG MOPA system as the pump source, the maximal average output powers of 3.15 W at 8.2 μm and 11.4 W at 2.8 μm were achieved in a ZGP OPO. The peak wavelength and linewidth (FWHM) of the long-wave infrared laser were 8156 nm and 270 nm, respectively. At the maximal output level, the pulse width and beam quality factor M2 were measured to be 8.10 ns and 6.2, respectively.
Highlights
As an important atmospheric transmission window, long-wave infrared lasers (8–12 μm) have been extensively applied in many fields, such as lidar, spectroscopy, and national defense [1,2]
We demonstrate a high-energy, narrow-pulse-width, long-wave infrared laser with repetition frequency of 1 kHz based on a ZGP crystal
The experimental setup of the Ho:YAG master oscillator power-amplifier (MOPA) system is shown in Figure 1, which contains a Q-switched Ho:YAG oscillator and a three-stage Ho:YAG MOPA system
Summary
As an important atmospheric transmission window, long-wave infrared lasers (8–12 μm) have been extensively applied in many fields, such as lidar, spectroscopy, and national defense [1,2]. Among the many ways to obtain a long-wave infrared laser, the optical parametric oscillator is an attractive approach due to its wide wavelength-tuning range and high conversion efficiency [3]. Nonlinear crystals suitable for generating a long-wave infrared laser mainly include OP-GaAs, AgGaSe2 , CdSe, BaGa4 Se7 , and ZnGeP2 (ZGP). The nonlinear coefficient of OP-GaAs is very large (d14 = 94 pm/V), and it was used to achieve an average pulse energy of 0.18 mJ at 8.5 μm [4] and 16.2 μJ at 10.6 μm [5], corresponding to the repetition frequencies of 2 and 50 kHz, respectively. AgGaSe2 has a low damage threshold (18 MW/cm2 ), which limits its ability to obtain a large-energy long-wave infrared laser. The highest energy of a long-wave infrared laser by AgGaSe2 was about hundreds of microjoules [6,7,8].
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