Highly efficient, ultra-broadband mid infrared generation driven by a Tm-doped fiber laser system

Abstract

We present on the nonlinear downconversion of a post-compressed Tm-doped fiber laser system via intrapulse difference frequency generation. In a preliminary experiment, with sampled 15 fs driving pulses and a 3 mm Gallium Selenide crystal, we achieved an octave spanning spectrum (5-16 µm) with a conversion efficiency of 3.6%. Utilizing the full 100 W driving laser power, we believe that this approach can pave the way towards W-class emission in the molecular fingerprint region enabling unprecedented sensitivity and precision in future spectroscopic applications.

Multi-octave coherent mid-infrared supercontinuum generation out to 11 µm via intra-pulse difference frequency generation in ZGP

“…Thulium (Tm) doped fiber lasers operating around 2 μm enable the use of readily available nonlinear crystals such as gallium selenide (GaSe) and zinc germanium phosphide (ZGP), which have broadband transmission in the MIR. IPDFG with conversion efficiency as high as 3.6% has been reported using GaSe pumped by a mJ-level Tm-doped fiber laser [4]. We have already demonstrated supercontinuum in the molecular fingerprint region based on a fiber laser and IPDFG in ZGP with 5.8% internal efficiency [6].…”

“…Alternatively, MIR pulses with super-octave spectra can be generated via intrapulse difference frequency generation (IPDFG). In this process, few-cycle pulses from a near infrared (NIR) laser pass through a non-linear crystal and different spectral components within the same pump pulse interact with each other, resulting in emission of longer wavelengths in the MIR region [1][2][3][4]. Several few-cycle pump sources and nonlinear crystals have been proposed and demonstrated.…”

“…Several few-cycle pump sources and nonlinear crystals have been proposed and demonstrated. But systems pumped by femtosecond (fs) fiber lasers are particularly attractive due to their robust and low-cost architecture [1,3,4]. Thulium (Tm) doped fiber lasers operating around 2 μm enable the use of readily available nonlinear crystals such as gallium selenide (GaSe) and zinc germanium phosphide (ZGP), which have broadband transmission in the MIR.…”

“…We demonstrate that efficient IPDFG signals with output powers as large as 39 mW and conversion efficiencies as high as 8.2%. It is worth noting that this conversion efficiency is obtained without using powerful pumps (μJ or mJ pulses) with complex architectures [2,4] or employing elaborate pump pulse compression techniques [4].…”