Milliwatt-level frequency combs in the 8–14 μm range via difference frequency generation from an Er:fiber oscillator

Abstract

We report on the generation of mid-infrared (mid-IR) pulses with a maximum average optical power of 4 mW and wide tunability in the 8-14 μm range via difference frequency generation (DFG) in GaSe from an Er:fiber laser oscillator. The DFG process is seeded with self-frequency shifted Raman solitons that are shown to be phase coherent within the whole tuning range, from 1.76 to 1.93 μm. Interference measurements between adjacent pulses at the idler wavelengths attest coherence transfer to the mid-IR.

High-power frequency comb source tunable from 27 to 42 μm based on difference frequency generation pumped by an Yb-doped fiber laser

“…While the lack of fCEO is a drawback in detection schemes using tight lock of the comb to an enhancement cavity [6], it is advantageous in other cavityenhanced techniques, like continuous-filtering Vernier spectroscopy [7]. The variety of nonlinear crystals available today enable generation of radiation up to 13-17 μm using GaSe [8], AgGaSe2 [9], CdSiP2 [10], or OP-GaAs [11] with output power at the level of few to tens of mW. However, DFG comb sources based on PPLN crystals are still very attractive because of high conversion efficiency and wide availability of the crystals, even though the transmission window of lithium niobate is limited to 5 μm.…”

Frequency comb generation in continuously pumped optical parametric oscillator

“…Applications such as molecular spectroscopy [21,22] would greatly benefit from a technology that allows for more straightforward and efficient generation of mid-IR frequency combs than existing solutions based on nonlinear transfer of near-IR OFCs [23][24][25][26][27][28][29][30][31][32][33]. Indeed, direct generation of frequency combs in the mid-IR region is hindered by the lack of available mode-locked lasers and nonlinear fibres.…”

Direct generation of optical frequency combs in χ(2) nonlinear cavities

“…More recently, mid-infrared OFCs have been observed in quantum cascade lasers, both in the mid-infrared and terahertz ranges [9][10][11], and attempts at modeling their dynamics are in progress [12][13][14][15]. Materials with second-order susceptibility, χ (2) , have been used to indirectly replicate or extend an existing frequency comb, otherwise generated, to different spectral regions, exploiting different χ (2) processes, like difference frequency generation [16][17][18][19][20][21][22][23], parametric generation in synchronously pumped optical parametric oscillators (OPOs) [24][25][26][27][28], and harmonic up-conversion [29][30][31]. Quadratic nonlinear crystals have been exploited in laser cavities for mode-locked emission: acting as electro-optic modulator in active mode-locking schemes [32,33], and as nonlinear mirror or nonlinear lens in passive schemes [34][35][36].…”