Hybrid Q-switched laser with MoS2 saturable absorber and AOM driven sub-nanosecond KTP-OPO

Investigations of 2D PtS2’s Saturable Absorption Characteristic and Its Optimization to OPO’s Operation

A 6.2 nm-thickness platinum disulfide (PtS₂) film was prepared by electron beam evaporation with post vulcanization. The nonlinear transmittance was measured by power scanning method and the modulation depth is fitted to be 13%. Based on the transmittance curve, saturable absorption parameters of PtS₂ are calculated with inhomogeneously broadening mechanism, including 6.4298 × 10⁻¹⁹ cm⁻² ground-state absorption cross-section, 2.5927 × 10⁻¹⁹ cm⁻² excited-state absorption cross-section, and 1.043 ms excited-state lifetime. The PtS₂ film combined with active time management was implemented to modulate the fundamental light of optical parametric oscillator (OPO). Owing to the nonlinear absorption property of PtS₂, the operation of Q-switched OPO was optimized in both the experiment and dynamical theory. In particular, the conversion efficiency was experimentally improved by 13.2%. The pump-to-signal conversion efficiency went up to 3.29%, which is the highest conversion value reported so far. The theoretical values fit the experiment well, which are from the Gaussian rate equations with PtS₂’s saturable-absorption characteristic.

High-peak-power 786 nm and 452 nm lasers based on 1064 nm intracavity-driven cascaded nonlinear optical frequency conversion

We demonstrated high-peak-power 786 nm and 452 nm lasers based on 1064 nm intracavity-driven cascaded nonlinear optical frequency conversion (CNOFC). The 1064 nm fundamental wave generated from the LD-side-pumped Nd:YAG was first intracavity converted to 1572 nm by a noncritically phase-matched KTP OPO. Then a LBO-based second harmonic generation of 1572 nm was served as cascaded process to produce 786 nm laser radiation. The maximum average output power at 786 nm was 1.34 W, corresponding to a pulse peak power of 14.2 kW with 11.2 ns pulse width and 8 kHz pulse repetition rate. Furthermore, a third stage of sum frequency mixing between 786 nm and 1064 nm was designed to achieve the blue emission at 452 nm. The 452 nm blue laser delivers 263 mW, 6.2 ns pulses with a peak power of 5.3 kW, paving the way for achieving high-peak-power blue lasers.

Experimental and dynamical study of a dual Q-switched intracavity OPO based on few-layer MoSe2 SA

A 2.5nm-thickness molybdenum diselenide (MoSe₂) saturable absorber (SA) is prepared by electron beam evaporation (EBE) method. Applying the prepared MoSe₂ SA to an acousto-optic (AO) Q-switched fundamental laser, a dual-loss-modulated intra-cavity optical parametric oscillator (IOPO) has been experimentally realized. The signal-pulse train from this IOPO has 0.0053 standard deviation (SD) of pulse amplitude. When the MoSe₂ SA is applied to IOPO, the signal pulse is compressed by maximum 68%, the peak power increases by 274%, and the nonlinear conversion increases by 12.6%. To solve the established rate equation of IOPO, the ground-state and excited-state absorption cross section of MoSe₂ are rationally estimated to be 1.04×10^-18cm^-2 and 6.25×10^-19cm^-2 from the measured transmittance curve, and the excited-state lifetime is 275.6µs. The numerical solution of the equations fits the experimental data well.