Femtosecond-laser pumped CdSiP_2 optical parametric oscillator producing 100  MHz pulses centered at 62  μm

Abstract

We report the first, to the best of our knowledge, femtosecond-laser-pumped optical parametric oscillator (OPO) based on the newly developed nonlinear crystal, CdSiP₂. The OPO was synchronously pumped by a mode-locked Yb:KYW/Yb:fiber master-oscillator power amplifier, providing 1.053 μm pump pulses with durations of 130 fs at a repetition rate of 100 MHz. The 0.5-mm-thick CdSiP₂ crystal was cut for a type-I noncritical interaction, providing a broad phase-matching bandwidth and ensuring excellent temporal overlap among the pump, signal, and idler pulses. The OPO generated signal pulses with a spectral coverage over 1260-1310 nm and mid-infrared idler pulses with a broad spectral coverage at 5.8-6.6 μm (6.2 THz). With a 2% output coupler (OC), the threshold pump power was 600 mW. At the maximum pump power of 1.6 W, 0.55 W was absorbed due to two-photon absorption and residual linear absorption in the CdSiP₂ crystal, 0.75 W was transmitted, and 53 mW signal power was extracted through the OC. We estimate that the generated idler power was 24 mW.

High-power femtosecond mid-infrared optical parametric oscillator at 7 μm based on CdSiP_2

“…Using a simple two-photon absorption model, we fitted the measured data for two-photon absorption coefficient (β), resulting in a value of β o 0.27 cm∕GW for o-polarization and β e 0.22 cm∕GW for e-polarization. These values of the two-photon absorption coefficient are lower than those measured using high-repetition-rate picosecond pulses at 1064 nm [8] and significantly lower than the value measured for the e-polarization using femtosecond pulses at 1053 nm [9]. This difference in the transmission characteristics could be attributed to the low repetition rate of the pump laser used in the present experiment.…”

“…The corresponding drop for e-polarization is from 95% to 90%, implying better transmission for the required pump polarization for phase-matching. These measurements indicate better transmission characteristics than those previously reported [8,9], despite operating at very high intensities. Using a simple two-photon absorption model, we fitted the measured data for two-photon absorption coefficient (β), resulting in a value of β o 0.27 cm∕GW for o-polarization and β e 0.22 cm∕GW for e-polarization.…”

“…Very importantly, CSP can also be pumped near 1 μm under noncritical phase-matching (NCPM) to generate mid-IR radiation in the 6-8 μm wavelength range. Earlier reports on ultrafast frequency conversion sources based on CSP include optical parametric generators [7] and OPOs [8] in the high-energy picosecond as well as femtosecond time-scales [9]. However, achieving high average output powers in the mid-IR wavelength range has been challenging.…”

Synthesis and Crystal Structures of the Calcium Silicon Phosphides Ca2Si2P4, Ca3Si8P14 and Ca3Si2P4

“…Therefore, it can be pumped by commercially available 1 μm laser. [15,16] However, it still requires more efficient NLO crystals that can be pumped by 1 μm laser.…”

Long-wave infrared generation from femtosecond and picosecond optical parametric oscillators based on orientation-patterned gallium phosphide

“…GaSe, the only material with a comparable figure of merit, has limited applications as the crystal is impossible to cut at certain phase-matching angles and it suffers from high linear absorption [36]. [11] with additional information added on OPGaAs [12,13], OPGaP [14,15], ZGP [16], CSP [17,18], PPLN [19] and PPKTP [20]. Greyed out regions show transmission which cannot be used for an OPO due to two-photon absorption or a lack of phasematching As this summary illustrates, practical choices for longwave mid-IR generation with an optimal choice of pump laser and tuning range are very limited.…”