Ti:sapphire-pumped deep-infrared femtosecond optical parametric oscillator based on CdSiP2

Critically phase-matched Ti:sapphire-laser-pumped deep-infrared femtosecond optical parametric oscillator based on CdSiP2

We report a high-repetition-rate femtosecond optical parametric oscillator (OPO) for the deep-infrared (deep-IR) based on type-I critical phase-matching in CdSiP₂ (CSP), pumped directly by a Ti:sapphire laser. Using angle-tuning in the CSP crystal, the OPO can be continuously tuned across 7306-8329 nm (1201-1369  cm^-1) in the deep-IR. It delivers up to 18 mW of idler average power at 7306 nm and >7  mW beyond 8000 nm at 80.5 MHz repetition rate, with the spectra exhibiting bandwidths of >150  nm across the tuning range. Moreover, the signal is tunable across 1128-1150 nm in the near-infrared, providing up to 35 mW of average power in ∼266  fs pulses at 1150 nm. Both beams exhibit single-peak Gaussian distribution in TEM₀₀ spatial profile. With an equivalent spectral brightness of ∼5.6×10²⁰photons s^-1 mm^-2 sr^-10.1% BW^-1, this OPO represents a viable alternative to synchrotron and supercontinuum sources for deep-IR applications in spectroscopy, metrology, and medical diagnostics.

30.5-μJ, 10-kHz, picosecond optical parametric oscillator pumped synchronously and intracavity by a regenerative amplifier

We have proposed a novel approach to realize a high-energy ultrafast optical parametric oscillator (OPO) by intracavity pumping in a regenerative amplifier. In this way, we have experimentally demonstrated an unprecedented pulse energy of 30.5 μJ from a 1.5-μm singly resonant synchronously pumped OPO at a pulse repetition rate of 10 kHz with a pulse width of 7.0 ps. To the best of our knowledge, this is the highest pulse energy from an ultrafast laser OPO.

Efficient, 2-5 μm tunable CdSiP2 optical parametric oscillator pumped by a laser source at 1.57 μm

We report on first demonstrations of CdSiP₂-based optical parametric oscillators that are pumped by eye-safe Q-switched nanosecond laser sources operating at 1.57 μm. One device reached 40% optical conversion efficiency generating 10 mJ of energy near degeneracy in the 3 μm region. Angle tuning of a similar device through the middle infrared was demonstrated with the signal and idler waves being tuned from 2.28 μm to 5.05 μm.

Spectral-temporal dynamics of high power Raman picosecond pulse using H2-filled Kagome HC-PCF

We report on the spectral-temporal characterization of a 1.8 μm wavelength and high power picosecond pulse Raman source. It is generated via frequency conversion to the first-order Stokes of a 27 ps chirped pulse Yb-doped fiber laser inside a molecular hydrogen-filled Kagome hollow-core photonic crystal fiber (HC-PCF). Depending on the average power and chirp of the pump laser, the average power of this Raman source can be as high as 9.3 W, and its pulse duration can be as short as ∼17  ps. In agreement with stimulated Raman scattering under the very high gain transient regime, the experimental results show the Stokes spectral structure to change following a three-stage sequence when the average pump power is increased. For a pump with a chirp corresponding to a bandwidth of 200 GHz, we found that for a pump power lower than 7 W, the Stokes spectrum is generated from the blue side of the pump spectrum, and then it exhibits a spectral replica of the pump spectrum for 7-14 W pump power range. Finally,the Stokes spectrum is chiefly generated from the red side of the pump spectrum when the pump power is further increased. Conversely, the Stokes pulse temporal profile shows a strong dependence with the pump power. For a low pump power range, the Stokes pulse exhibits a single peak with a full width at half-maximum of ∼17  ps. For higher pump powers, the Stokes pulse presents a double-peak structure with each peak having a duration of less than 15 ps. The present results can be used to develop compact and efficient frequency down-convertors to the increasingly widespread Yb-based picosecond lasers.

High-repetition-rate, deep-infrared, picosecond optical parametric oscillator based on CdSiP2

We report a high-repetition-rate picosecond optical parametric oscillator (OPO) based on CdSiP₂ (CSP) that is synchronously pumped by an Yb-fiber laser at 1064 nm and provides high average power in the deep-infrared (deep-IR) at 79.5 MHz. The OPO is tunable across 6205-6710 nm in the idler, providing as much as 105 mW of average power at 6205 nm and >55  mW over nearly the entire tuning range. The deep-IR idler output exhibits passive power stability better than 2.3% rms over 12 h in good beam quality. The near-IR signal pulses from the OPO have a Gaussian pulse duration of ∼19  ps, measured at 1284 nm. We have investigated the temperature tuning characteristics of the OPO and compared the data with the theoretical calculations using the most recent Sellmeier equations and thermo-optic coefficients for the crystal. To the best of our knowledge, this is the first picosecond OPO based on CSP operating at MHz repetition rates.

Molecular fingerprint-region spectroscopy from 5 to 12 μm using an orientation-patterned gallium phosphide optical parametric oscillator

We report a femtosecond optical parametric oscillator (OPO) based on the new semiconductor gain material orientation-patterned gallium phosphide (OP-GaP), which enables the production of high-repetition-rate femtosecond pulses spanning 5-12 μm with average powers in the few to tens of milliwatts range. This is the first example of a broadband OPO operating across the molecular fingerprint region, and we demonstrate its potential by conducting broadband Fourier-transform spectroscopy using water vapor and a polystyrene reference standard.

Pump-tuned deep-infrared femtosecond optical parametric oscillator across 6-7 μm based on CdSiP2

We report on a high-power femtosecond optical parametric oscillator (OPO) at 80 MHz repetition rate, tunable across 6318-7061 nm in the deep-infrared (deep-IR) using pump wavelength tuning. The OPO, based on CdSiP₂ (CSP), is synchronously pumped by a commercial Ti:sapphire-pumped femtosecond OPO in the near-IR, enabling rapid static tuning of the CSP OPO with minimal adjustments to its cavity length. The deep-IR CSP OPO provides as much as 32 mW of average idler power at 6808 nm with spectral bandwidth >1000  nm (at -10  dB level) across the tuning range. By implementing intracavity dispersion control, near-transform-limited signal pulses of ∼100  fs duration with smooth single-peak spectrum are achieved at 1264 nm, corresponding to an idler wavelength at 6440 nm. To the best of our knowledge, this is the first time such practical idler powers in the deep-IR have been generated from a dispersion-compensated CSP femtosecond OPO at sub-100 MHz repetition rate.