CC BY
15ALT'22
LS-I-5
LASER SYSTEMS AND MATERIALS
Mid-Infrared Ultrashort Pulse Raman Lasers based on Gas-Filled Revolver Silica Fibers
A.V. Gladyshev, A.F. Kosolapov, I.A. Bufetov
Prokhorov General Physics Institute of the Russian Academy of Sciences, Dianov Fiber Optics Research Center, 38
Vavilov st., Moscow, Russia, 119991.
*Corresponding author: [email protected]
Mid-infrared (mid-IR) ultrashort pulse (USP) lasers are required for a wide range of applications. One of the promising approaches to generate USP in the mid-IR is the concept of gas fiber Raman lasers, which has been successfully used to generate USP at 1.8 and 2.68 mm [1-3]. Here, we extend this approach to longer wavelength and demonstrate efficient USP Raman conversion to wavelength as long as 3.9 mm in a gas-filled hollow-core silica fiber (HCF).
The experimental setup and the HCF properties were reported elsewhere [3]. The HCF was filled by H2/D2 gas mixture and pumped by 1.03-mm 250-fs-long pulses that were stretched to 12 ps in duration to promote efficient stimulated Raman scattering (SRS). Total pressure of the mixture was fixed at 30 bar.
At H2 partial pressure of 25 bar two-cascade SRS based on H2 and D2 vibrations was achieved via two complementary schemes 1.03—>1.8—>3.9 mm and 1.03—1.49—3.9 mm, thus generating a vibrational Stokes component at 3.9 mm. Quantum efficiency about 10 % was demonstrated for 1.03—3.9 mm conversion, and pulse energy as high as 5 mJ was achieved at 3.9 mm.
The results obtained may be used to develop mid-IR laser sources of various types, such as frequency combs, super-continuum and few-cycle pulse sources, which are promising for a wide range of applications.
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Fig. 1. (a) Spectrum measured at the output of the 2.9-m-long silica HCF that was filled by H2/D2 gas mixture and pumped by 80-pJ 12-ps-long pulses at A=1.03 mm. Partial pressures of H2 and D2 were 25 and 5 bar, respectively. The spectrum includes the following vibrational Stokes components: 1st and 2nd Stokes in deuterium (S1(D2) and S2(D2)), 1st Stokes in hydrogen (S1(H2)) and two-cascade Stokes that involves both deuterium and hydrogen (S2(H2+ D2)). (b) The output number of photons at pump (black dots), 1st Stokes (blue dash-dots) and 2nd Stokes (red solid line) wavelengths as a function of coupled pump pulse energy. The curves are normalized to the number of coupled pump photons. The total photon number is also shown (dashed black line).
This work is supported by Russian Science Foundation (grant №19-12-00361).
[1] S. Loranger et al., "Sub-40 fs pulses at 1.8 (im and MHz repetition rates by chirp-assisted Raman scattering in hydrogen-filled hollow-core fiber," J. Opt. Soc. Am. B, 37, 3550-3556 (2020).
[2] N. V. Didenko et al., "On the possibility of generation of few-cycle 1.8 mm pulses based on SRS in hydrogen," Laser Phys. Lett., 18, 125001 (2021).
[3] A. Gladyshev et al., "Mid-infrared 10-(J-level sub-picosecond pulse generation via stimulated Raman scattering in a gas-filled revolver fiber," Opt. Mater. Express 10, 3081-3089 (2020).
