A passively Q-switched dual-wavelength laser with coaxial diode end-pumping configuration is demonstrated. A theoretical model was built to simulate the dynamic process of dual-wavelength laser pulse generation. The experiment was performed with Nd:YVO4/Nd:GdVO4 composite laser crystals and a Cr4+:YAG absorber. The continuous-wave and Q-switched output power reached 3.48 W and 607 mW, respectively, under the maximum LD pump power of 8.0 W, corresponding to optical-to-optical conversion efficiencies of 43.5% and 7.6%. The power ratio between 1064.4 nm and 1063.5 nm could be tuned by varying the pump wavelength to balance the gains in two laser crystals.
A multi-wavelength green laser is presented based on a coaxial diode-end-pumping configuration by intracavity frequency doubling with a nonlinear crystal. The composite gain media (Nd:YVO4 and Nd:GdVO4) are placed coaxially and share one pump diode around 808 nm to generate two competition-free fundamental laser at 1064.4 nm and 1063.2 nm. The nonlinear crystal (KTP or LBO) are satisfactory for second-harmonic generation (SHG) and sum-frequency generation (SFG) with different fundamental wavelengths. Stable multi-watt green lasers at 532.2 nm, 531.6 nm and 531.9 nm are simultaneously obtained. Through gain controlling by tuning the pump focusing depth and pump absorption, the power ratio for those wavelengths and pulse interval can be manipulated actively. A rate-equation model is proposed and the experimental results coincide with the simulations. By replacing the gain media (Nd:YAG, Nd:GSGG, Nd:YAP, etc), various green lasers with multiple and selectable wavelengths are possible, which have great potential in practical applications.
A compact and flexible dual-wavelength eye-safe intracavity optical parametric oscillator (IOPO) configuration driven by a coaxially end pumped laser was proposed. Two fundamental waves were provided by a coaxially end pumped Qswitched dual-wavelength laser with combined two laser crystals, and the OPO cavity was placed inside the laser cavity for efficient conversion. Theoretical simulations showed that the power ratio for each signal wave, as well as the time interval between two pulses at different wavelengths, were both tunable by tuning the pump focusing depth or pump wavelength. Experimental results were performed with combined laser crystals (Nd:YAG and a-cut Nd:YLF) and a nonlinear crystal (KTA), demonstrating coincident conclusions. The maximum OPO output power was 724 mW (388 mW at 1506 nm and 336 mW at 1535 nm) with the LD pump power of 10 W at 6 kHz, corresponding to the opticaloptical conversion efficiency of 7.24%. As there was no gain competition between two fundamental waves, stable signal output could be obtained. Moreover, various wavelength pairs can be generated by using different laser crystal combinations. It is believed that this is a promising method for simultaneously generating dual-wavelength eye-safe lasers pulses.
Theoretical simulations were carried out to evaluate the properties of terahertz (THz) generation in β-BaTeMo2O9 (βBTM) crystal by stimulated polariton scattering (SPS) process. The effects of different polariton modes on THz generation were analyzed, from which we determined the optimal crystal design and polarizations of the coupled waves. The dispersion and absorption characteristics of these vibration modes were also given based on the first-principle calculation and correlation Raman spectrum. Finally, the angle phase matching property and THz-wave gain were calculated. Simulation results showed that β-BTM is a kind of potential material for high-power tunable THz generation.
A compact and flexible dual-wavelength laser with combined two laser crystals (a-cut and c-cut Nd:YLF) as the gain media under coaxially laser-diode (LD) end-pumping configuration was demonstrated and μW-level THz wave was generated based on difference frequency generation (DFG) in a GaSe crystal. The dynamics of coaxial pumping dualwavelength laser was theoretically investigated, showing that the power ratio and pulse interval for both wavelengths could be tuned by balancing the gains at both wavelengths via tuning pump focal position. Synchronized orthogonal 1047/1053 nm laser pulses were obtained and optimal power ratio was realized with the total output power of 2.92W at 5 kHz pumped by 10-W LD power. With an 8-mm-long GaSe crystal, 0.93 μW THz wave at 1.64 THz (182 μm) was generated. Such coaxially LD end-pumped lasers can be extended to various combinations of neodymium doped laser media to produce different THz wavelengths for costless and portable applications.