•It comparative studied intra-cavity THG between single- and multi-pass operations.•The first THG plays a key role, which accounts for more than 70% of all power.•The single-pass operation will be more useful in efficient THG laser.Intra-cavity third harmonic generation was investigated comparatively in both single- and multi-pass operations from a side-pumped acousto-optic Q-switched Nd:YAG laser. Under the pump current of 19 A, 1.68 W and 2.2 W output power at 355 nm were obtained at 9.5 kHz in single and multi-pass THG operation respectively, with a power ratio of 76%. It clarified that the first THG process in multi-pass operation played a key role in the whole frequency-tripling process. The result provided the issue that efficient third harmonic laser could be achieved via optimizing the intra-cavity single-pass THG operation due to its high beam quality.

•Transparent Yb3+ and Er3+ co-doped Y3Al5O12 (Yb, Er:YAG) ceramics have been synthesized simply.•The structural, optical, and spectroscopic properties were investigated in detail.•The 1.6 μm laser was realized with the commercial laser diode at 970 nm.We reported a kind of Yb3+ and Er3+ co-doped Y3Al5O12 (Yb, Er:YAG) transparent ceramics fabricated by using one-step vacuum sintering. The decent optical properties of the samples, e.g., high in-line transmittance up to 83.4% (at 1.6 μm), are benefit from their fine structures, in which the average grain size is 15 μm, without any pores spotted within the scope. The absorption around 970 nm of this co-doped ceramic reaches nearly 4.8 times that of the single Er3+ doped YAG. Laser operation at 1645 nm was evaluated by using a commercial laser diode emitting at 970 nm. The maximum output power of 155 mW was acquired with an optical-to-optical efficiency of 2.8%.

•We experimentally investigated the performance of diode-wing-pumped Tm:YAG laser.•We compared the laser performance between composite and non-composite crystals.•We compared laser spectra features between composite and non-composite crystals.•Red-shift of the laser spectra was experimentally observed.•Power scaling can be realized by using composite crystal with short doped segment.We experimentally investigated the performance of diode-wing-pumped Tm:Y3Al5O12 crystalline laser operating at around 2 μm. By systematically making comparisons of laser performance in addition to the laser spectra features between composite and non-composite crystals with two different active segments length, we believed that using diffusion-bonded crystal with shorter Tm3+-doped active segment would be a feasible approach for simultaneously up-scaling the output power and slope efficiency in terms of reducing the reabsorption loss and thermal lensing effects.

In this study, a compact and efficient Nd:YLF laser at 1053 nm has been reported without inserting optical intracavity element to suppress the stronger line of 1047 nm. According to theoretical analysis and calculation, the thermal focal length of 1047 nm is negative while that of 1053 nm is positive in plane-parallel resonator. Hence 1053 nm laser was stable in this cavity. In our experiment, 7.5 W laser output at σ-polarized 1053 nm has been obtained with optical–optical efficiency of 38.8%. As the pulse repetition rate is 20 kHz, the pulse width is 50 ns and the peak power is calculated to be 7.5 kW.

In this paper, a practical method for obtaining the exact absorption coefficient of optical media was presented, which can be applied to amend the error attributed to multi-reflections. According to the materials' transmissivities and refractive indices, a formula was derived, which can be used for calculating the absorption coefficient. The feasible region with the relative error lower than 10% was represented by a mathematical expression. The calculated formula was confirmed to be applicable to optical materials with strong-absorbent (>0.1 cm−1), especially laser or Raman media. This study can provide a useful approach for getting exact absorption coefficients of new optical materials and other derivative parameters.Highlights► The systematic study for obtaining the exact absorption coefficient of solid material is reported. ► The relative error distribution in the calculation of the absorption coefficients is analyzed. ► The feasible region of the calculation is got with the relative error lower than 10%. ► This is a practical method for strong-absorbent materials, especially for laser or Raman mediums.

In this paper, a continuous-wave (CW) diode-side-pumped Nd:YAlO3 (Nd:YAP) laser operating at the weak line of 1339 nm has been achieved and investigated. The output of the 1339 nm laser was realized based on the polarization selection and reasonable transmittance design. The relationship between the output powers and resonator lengths of the 1339 nm Nd:YAP laser has been studied and the optimum resonator length was adopted to improve the output power. As high as 31.3 W output power of the a-axis polarized 1339 nm laser has been obtained at the pumping power of 555 W with the optical–optical and slope efficiencies to be 5.6% and 13%, respectively. This work will provide an effective way to obtain the weak line lasers for potential applications in spectroscopy, coherent terahertz generation, etc.

In this paper, a stable end-pumped intracavity-frequency-doubled green laser was demonstrated. The interaction length of different pump systems before setting up the experiment was analyzed in order to find out an effective pump system. The experimental results indicate that the pump system in our configuration is beneficial to the efficient CW Nd lasers. A continue-grown composite crystal YVO4/Nd:YVO4, with Nd3+ concentration doping of 0.3 at.%, is used as laser medium. With an incident pump power of 27.5 W, as high as 7.2 W of CW output power at 532 nm was achieved. The optical-to-optical conversion efficiency of 26.2% was obtained in CW modes with a flat–flat cavity design.

An eye-safe, high peak power optical parameter oscillator (OPO) intracavity pumped by electro-optic Q-switched Nd:YAG laser is presented. This OPO is based on a 20 mm length KTiOAsO4 crystal with non-critical phase matching (θ = 90°, ϕ=0°ϕ=0°) cut. An aperture ∅3 mm acted as limiting diaphragm to get good beam quality of pumping laser. The output energy of 25 mJ at the signal wavelength 1.53 μm was obtained with repetition rate of 1 Hz. The highest peak power intensity was up to 88 MW/cm2 with pulse width of 4 ns. Without diaphragm, the maximum output energy of 90 mJ was achieved with area of light spot (∅6 mm) four times larger, but the peak power intensity was lower.

The laser oscillating at a weak line of Nd:YAP around 1.3-μm realized though selecting polarization is described. The energy level transitions of Nd:YAP crystal and their polarization properties were analyzed. A thin-film polarizer was adopted to restrain the oscillating of the c-axis strong polarized spectral lines and a reasonable transmittance was designed to suppress the a-axis polarized 1064 nm strong line lasing, and then a-axis polarized 1339 nm pulse laser of 336 mJ for free running mode and 64 mJ for electro-optic Q-switched mode were successfully achieved, corresponding to pulse widths of 180 μs and 35 ns, respectively. This method of selecting polarization to realize weak line oscillating is significant for anisotropic laser crystals doped with Nd3+ ions to select the particular transitions.

The principal refractive indices of Ca9La(VO4)7 crystal for wavelengths of 0.488, 0.6328, 1.064 and 1.338 μm under the temperature range from 30 °C to 170 °C were measured by auto-collimation method. The Sellmeir-equations of Ca9La(VO4)7 crystal at different temperatures have been obtained based on the experimental data, and the refractive indices of some wavelengths in different temperatures are calculated by the Sellmeir-equations and compared with the corresponding measured values in order to check their reliability. As a result, the difference between the calculated results and the measured results is not more than 1 × 10−4. The theoretical PM (phase matching) angles of SHG (second harmonic generation) built on the experimental refractive indices are also given.

In this paper, the study of a switchable electro-optic Q-switched Nd:YAlO3 laser emitting 1080 and 1342 nm wavelength was demonstrated. The two-wavelength lasers were eradiated by a Nd:YAlO3 crystal pumped by a xenon lamp. Two KD*P Pockels cells were adopted as Q-switches. The output energy of 277.2 mJ at 1080 nm wavelength with a pulse width of 20 ns and that of 190.67 mJ at 1342 nm wavelength with a pulse width of 40 ns was obtained, respectively, in our experiment. By switching on or off the voltages applied to the Pockels cells, the operation of the two-wavelength lasers can be selected in free running mode or Q-switching mode.

In this paper, a flash-lamp pumped 1.3414 μm Nd:YAP Q-switched pulse laser are presented. The experimental results for about 45 ns of pulse duration and more than 300 mJ of output energy have been obtained and discussed.

Through reasonable coating design to suppress the 1064 nm strongest emission line as well as the 1318.8 nm one, a 1338 nm high-power Nd:YAG quasi-continuous wave (QCW) laser pumped with a Kr lamp has been successfully developed. As high as 102 W of average output power at the 1338 nm single wavelength has been obtained with the overall and slope efficiencies of 4.6% and 6.3%, respectively, when the average pump power is 2200 W. Its threshold power is about 400 W.

The relationships between the temperatures and the principal refractive indices of 7.5 mol% Nb:KTP crystal is achieved from the measured refractive indices. The cutoff wavelengths of noncritical phase matching at different temperatures are calculated. Compared with the KNbO3 crystal, the Nb:KTP crystal shows the better performance for generating the blue light.