Influence of output coupling on the performance of a passively Q-switched Nd:YAG laser with intracavity optical parametric oscillator

Measurement of dynamic atomic polarizabilities of Al at 19 wavelengths from 420 nm to 680 nm in electrical exploding wire experiments

The dynamic polarizabilities of Al atom at 19 wavelengths from 420 nm to 680 nm are measured experimentally for the first time. A 15 µm diameter Al wire is heated to the gas/ microdrop stage using a 3 kA, 25 ns pulsed current, and the energy deposition when the resistive voltage reaches its peak is 4.7 eV·atom^-1, which is higher than the atomization enthalpy of Al but much lower than its first ionization potential. Two laser interferometric images of the Al gas are obtained simultaneously using a 532 nm laser and an optical parametric oscillator laser. Then an integrated phase method is used to reconstruct the Al atomic linear density distribution based on the known atomic polarizability at 532 nm, which acts as a bridge between the two interferograms to obtain the relative atomic polarizability value at a specific wavelength with respect to the value at 532 nm. The measured dynamic polarizability of Al atom decreases from 13.5×10^-24 cm³ to 9.4×10^-24 cm³ as the wavelength increases from 420 nm to 680 nm with a measurement error of approximately ±10%. The experimental result fits well with an uncoupled Hartree-Fock approximation, and the reconstructed static polarizability of 8.13 ± 0.79×10^-24 cm³ is well matched with reference measurement results.

Intracavity deformable mirror for beam quality improvement and power enhancement of a passively Q-switched laser

The performance of the passively Q-switched (PQS) laser deteriorates under high pumping power for the intracavity thermally induced wavefront distortion (thermal distortion for short). A new intracavity deformable mirror (DM) is proposed to compensate the thermal distortion of a PQS laser in this paper. The thermal distortion of the PQS laser is measured using the active deflectometry method. A simulation model is built to investigate the influences of the DM structure parameters on the surface shape of the DM (DMSS). Simulation results indicate that the DMSS matches well with the measured thermal distortion in the PQS laser at the given pumping current. Based on the simulation results, a low-cost, compact intracavity DM consisting of a mirror unit, a heater unit, a cooler unit and a base unit is built and used in the PQS laser. The DMSS is measured by a Zygo interferometer and coincides with the simulation result. In the improved PQS laser experiment, the optimum heater temperatures for the maximum output power and minimum M² at different pumping currents are measured and given. The output stability of the PQS laser with the DM is tested. By adjusting the heater temperature, the PQS laser could achieve optimum performance in different environmental temperatures with good temperature adaptability. Experiment results verify that the PQS laser with the designed DM could achieve high output power and good beam quality at high pumping currents, as the DM prominently compensates the thermal distortion in the laser.

RbTiOPO4 cascaded Raman operation with multiple Raman frequency shifts derived by Q-switched Nd:YAlO3 laser

An intra-cavity RbTiOPO₄ (RTP) cascade Raman laser was demonstrated for efficient multi-order Stokes emission. An acousto-optic Q-switched Nd:YAlO₃ laser at 1.08 μm was used as the pump source and a 20-mm-long x-cut RTP crystal was used as the Raman medium to meet the X(Z,Z)X Raman configuration. Multi-order Stokes with multiple Raman shifts (~271, ~559 and ~687 cm^-1) were achieved in the output. Under an incident pump power of 9.5 W, a total average output power of 580 mW with a pulse repetition frequency of 10 kHz was obtained. The optical conversion efficiency is 6.1%. The results show that the RTP crystal can enrich laser spectral lines and generate high order Stokes light.

Dual-loss-modulated Q-switched mode-locked laser intracavity pumped temperature-tuned subnanosecond KTiOPO4 optical parametric oscillator

Using an acousto-optic modulator (AOM) and Cr4+:YAG as the dual-loss modulation, an intracavity KTiOPO4 optical parametric oscillator (OPO) pumped by a simultaneously Q-switched and mode-locked (QML) YVO4/Nd:YVO4 laser was realized. The shortest mode-locking pulse duration of the signal wave at 1573 nm was directly measured as 450 ps at an AOM frequency of 2 kHz and a diode pump power of 10.5 W, corresponding to a peak power of 35.5 kW. The temperature tuning of the output signal wavelength was realized in the range from 1571.99 to 1572.61 nm with a blueshift ratio of 0.027  nm/°C. A set of coupled rate equations for the dual-loss-modulated QML laser pumping intracavity OPO was built for the first time to our knowledge. The numerical solutions were fitted with the experimental results.