Abstract
We have demonstrated a tunable mid-infrared tandem optical parametric oscillator (OPO) based on BaGa4Se7 (BGSe) crystal, which was intracavity-pumped by the tunable signal wave at ∼1 μm generated from a KTiOPO4-OPO (KTP-OPO) in doubly-resonant oscillator (DRO) configuration. Wavelength tuning of the mid-infrared tandem OPO was realized by tuning the pump wavelength at the fixed phase matching angle to reduce the effects of beam cutting and Fresnel reflection loss. Together with pump-tuning method, angle-tuning method was supplied to extend tuning range. A tuning range of 4.1–4.5 μm was obtained with just 5 individual phase matching angles of the BGSe crystal. The maximum output energy of 1.92 mJ/pulse was obtained at 4.26 μm with an estimated slope efficiency of 9.5%.
Highlights
The tunable mid-infrared wave sources in the wavelength range of 3–5 μm are especially important for wide applications, such as remote sensing, chemical detection, medicine, and national defense [1], [2]
The tunable λ1 generated by near degenerate point KTP-Optical parametric oscillator (OPO) in the first stage was adopted to pump the BGSe-OPO in the second stage
When the tandem OPO system was pumped at input 532 nm energy of 135 mJ/pulse, the maximum output energy of 1.92 mJ/pulse at 4.26 μm was obtained in the tandem OPO with M5
Summary
The tunable mid-infrared wave sources in the wavelength range of 3–5 μm are especially important for wide applications, such as remote sensing, chemical detection, medicine, and national defense [1], [2]. The newly developed BGSe crystal with high performances is considered as a very promising NLO crystal for widely tunable and high-energy mid-infrared wave generation, especially pumped at 1 μm [12]–[16]. BGSe crystals with long length (14.5–30 mm) have been employed in the widely tunable and high-energy mid-infrared OPO sources, which were pumped by different fixed wavelengths of 1.053 μm, 1.064 μm, 2.1 μm and 2.79 μm under type I and type II phase-matching (PM) conditions [17]–[22] with angle-tuning method. Pump-tuning method is an efficient method to realize tunable mid-infrared source, with the advantages of wide tuning range, stable output energy and easy tuning [23]. The characteristics of the output energy, wavelength tuning, temporal width and the beam divergence of the generated mid-infrared wave were investigated
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