Ho3+:LLF MOPA pumped RISTRA ZGP OPO at 3-5 µm

Georg Stoeppler; Martin Schellhorn; Marc Eichhorn

doi:10.1117/12.2004021

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12 March 2013 Ho³⁺:LLF MOPA pumped RISTRA ZGP OPO at 3-5 μm

Georg Stoeppler, Martin Schellhorn, Marc Eichhorn

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Proceedings Volume 8604, Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XII; 86040I (2013) https://doi.org/10.1117/12.2004021
Event: SPIE LASE, 2013, San Francisco, California, United States

Abstract

High pulse energies in the mid-IR with a comfortable tuning possibility are required in a number of areas, including remote sensing, medicine and counter measure applications. Frequency converters based on the crystal ZnGeP₂ (ZGP) are widely used for generating tunable IR radiation in the 2.5 μm - 12 μm region. ZGP possesses high nonlinearity, however, due to its limited transparency range it requires pump wavelengths longer than 2 μm. A significant drawback of ZGP and of most other IR non-linear crystals is a low damage threshold of ~ 1 J/cm² for nanosecond pulses. Therefore nanoseconds OPOs at pulse energies in the 10 mJ – 100 mJ range require large diameter pump beams to reduce the risk of optical damage to the crystal. We used the “Rotated-Image, Singly resonant, Twisted-RectAngle” (RISTRA) ring cavity concept to improve the beam quality of the OPO stage. A Tm³⁺ fiber laser pumped Ho³⁺:LuLiF₄ (Ho³⁺:LLF) MOPA system was developed delivering > 100 mJ at 2053 nm in TEM₀₀ operation at a repetition rate of 100 Hz. Using a RISTRA as a single OPO stage we demonstrated an overall OPO pulse energy of 23.8 mJ in the wavelength region 3 μm - 5 μm at a pump energy of about 45.6 mJ and a repetition rate of 100 Hz. The beam quality was measured to be M² ~ 2.5.

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Georg Stoeppler, Martin Schellhorn, and Marc Eichhorn "Ho³⁺:LLF MOPA pumped RISTRA ZGP OPO at 3-5 μm", Proc. SPIE 8604, Nonlinear Frequency Generation and Conversion: Materials, Devices, and Applications XII, 86040I (12 March 2013); https://doi.org/10.1117/12.2004021

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