Xueyuan Hou

Passively Q-switched 1.34 μm Nd:Y x Gd 1-x VO 4 laser with Co 2+ :LaMgAl 11 O 19 saturable absorber

The static and dynamic 1.34 mum laser output performance of the Nd:Y(x)Gd(1-x)VO(4) mixed crystal pumped by flash-lamp is investigated with different transmissions of output couplers (T=15%, 30% and 40%) in a plano-concave laser cavity. With the output coupler transmission of T=30%, the static output energy of 62 mJ is obtained when the pump energy is 24.2 J, and the corresponding electric-optical conversion efficiency is 0.26%. By using a new saturable absorber: Co(2+):LaMgAl(11)O(19) (Co:LMA), the passive Q-switching at 1.34 mum is realized when the second threshold condition of passive Q-switching is satisfied. With the cavity length of 245 mm and pump energy of 24.2 J, the single-pulse output energy, pulse width and peak power are obtained to be 3.5 mJ, 45 ns and 77.8 kW, respectively.

Plasma properties of a laser-ablated aluminum target in air

The optical emission spectra of the plasma generated by a 1.06-μm Nd:YAG laser irradiation of Al target in air was recorded and analyzed in a spatially resolved manner. Electron temperatures and densities in the plasma were obtained using the relative emission intensities and the Stark-broadened linewidths of Al(I) emission lines, respectively. The dependence of the electron density and temperature on the distance from the target surface and on the laser irradiance were manifested. We also discussed how the air takes part in the plasma evolution process and confirmed that the ignition of the air plasma was by the collisions between the energetic electrons and the nitrogen atoms through a cascade avalanche process.

Co 2+ :LaMgAl 11 O 19 saturable absorber Q-switch for a flash lamp pumped 1.54 μm Er:glass laser

By using a new saturable absorber, Co(2+):LaMgAl(11)O(19) (Co:LMA) crystal, the passive Q-switched operation of a flash lamp pumped 1.54 mum Er:glass laser is realized. With different transmissions of the output mirror, the properties of static output and dynamic output of the laser are studied. The experimental results show that, when transmission of the output coupler is 15%, the static output curve has higher slope efficiency and higher energy conversion efficiency and meanwhile the Q-switched output pulses with higher single-pulse energy and narrower pulse width can be obtained.

Analysis of a laser-diode end-pumped passively Q-switched Nd:GdVO4 laser with V3+:YAG saturable absorber

By considering both the transversal and longitudinal Gaussian spatial distribution of the intracavity photon density, a couple of rate equations describing a laser-diode end-pumped passively Q-switched Nd:GdVO4 laser with V3+:YAG saturable absorber have been proposed. Solving these space-dependent rate equations numerically, we obtain the dependences of pulse width, pulse repetition rate, single-pulse energy and peak power on pump power. In the experiment, a laser-diode end-pumped Nd:GdVO4 laser passively Q-switched by a V3+:YAG saturable absorber has been realized, and the experimental results are consistent with the theoretical calculations.

Laser characteristics of Cr:Nd:GdCOB self-frequency-doubling crystal

The phase matching angle of GdCOB crystal is calculated. By using Xenon flash lamp as pump source, we have realized the free run from 1.06 μm to 0.53 μm in self-frequency-doubling Cr:Nd:GdCOB (bi-doped) crystal and Nd:GdCOB (uni-doped) crystal. The experimental results show that the threshold energies for bi-doped crystal and uni-doped crystal are 0.92 J and 1.00 J, respectively; when the pump energy is 10 J, the output energies of green laser for two kinds of crystals are 2.46 mJ and 1.96 mJ, respectively. The output energy of Cr:Nd:GdCOB crystal has an increase of 25% in comparison to that of Nd:Gd:COB crystal. In addition, we discuss ways to improve efficiency.

Growth and properties of (Cr3+, Nd3+) doped GdCa4O(BO3)3 crystals

Abstract Optical quality Nd:GdCa 4 O(BO 3 ) 3 (Nd:GdCOB) crystal and chromium sensitized crystal of Cr:Nd:GdCa 4 O(BO 3 ) 3 (Cr:Nd:GdCOB) were grown by the Czochralski (CZ) method. The transmittance spectra was measured at room temperature on 7at%Nd:GdCOB and lat%Cr:7at%Nd:GdCOB samples. The absorption in the blue-UV region of Cr:Nd:GdCOB was larger than that of Nd:GdCOB, which matched the xenon flash lamp very well. A 3×3×10mm 3 Nd:GdCOB sample without any antireflective coating was sidepumped using a pulsed dye-laser tuned to 595.4nm. The green-light output energy was 1.35mJ at a pump energy of 17.5mJ. The conversion efficiency was 7.7%, and the threshold energy was less than 1.2mJ which are the best results up to now to our knowledge. 3×3×7mm 3 Nd:GdCOB and Cr:Nd:GdCOB samples without antireflective coatings were pumped using a flash pump source. The threshold for Cr:Nd:GdCOB was 0.9J while for Nd:GdCOB it was I.O.J. The output green light energy was 2.46mJ for Cr:Nd:GdCOB at a 10J flash pump energy and was 1.96mJ for Nd:GdCOB at the same pump energy, which clearly shows that Cr 3+ ions have the sensitizing effect on the Nd 3+ ions in Nd:GdCOB crystal.

Passively Q-switched Nd:GdVO4 laser with GaAs saturable absorber

Abstract A xenon flash-lamp-pumped, passively Q-switched Nd:GdVO4 laser with GaAs semiconductor saturable absorber is demonstrated. The static laser performance is investigated and the static output is 52 mJ when the pump energy is 9.45 J . The dynamic laser has the highest slope efficiency when the GaAs wafer is both the saturable absorber and output coupler. Pulses with duration of 64 ns and dynamic output of 47.6 mJ are obtained when the pump energy is 9.45 J . The highest dynamic–static ratio is 0.9:1. The coupled rate equations are used to simulate the Q-switched process of laser. The theoretical and experimental results are compared and discussed.

Space phase matching and self-frequency-doubling red laser in Nd:GdCOB crystal

Abstract By using the calculation theory of the phase-matching direction and effective nonlinear coefficient of frequency doubling in biaxial crystal, we calculate the effective nonlinear coefficients at different frequency-doubling phase-matching directions of the three main fluorescent lines (936, 1060, 1331 nm ) of Nd:GdCOB crystal. The space distribution curves of effective nonlinear coefficient are drawn. Two crystal specimens are cut at the optimal type I phase matching angles: for specimen 1, θ=65°, Φ=34.6° (the first octant); for specimen 2, θ=66.5°, Φ=145.5° (the second octant). When pumped by Datachroom-5000 pulsed dye laser, the output self-frequency-doubling red laser in specimen 2 is 0.62 mJ , and the corresponding conversion efficiency is 2.5%. Under the same pumping condition, the output red laser of specimen 1 is much smaller than that of specimen 2, which is well in agreement with the theoretical calculation.

Study on the Second-Harmonic Generation of YCa4O(BO3)3 Crystals along Various Phase-Matching Directions

Large size and high-quality YCa 4 O(BO 3 ) 3 (YCOB) crystal can be grown using the conventional Czochralski pulling method. The theoretical calculations of the effective coefficient (d eff ) and the walk-off angles at 530 nm of YCOB along various phase-matching (PM) directions are reported. The PM direction along (0 = 64.5°, φ = 144.5°) for YCOB crystal has the largest d eff- Second-harmonic generation (SHG) experiments were performed on YCOB crystal along various PM directions. The results show that in 6 mm long YCOB crystal, the SHG conversion efficiency is 39% along the PM direction (θ = 64.5°, φ = 144.5°) at 80 MW/cm 2 input power density, which is larger than that along (0 = 64.5°, φ = 35.5°) and the PM direction in the XZ main plane. The experimental result is in good agreement with the theoretical calculations.

Laser Self‐Frequency‐Doubling in NdxGd1—xCa4O(BO3)3

A large size and optical quality Nd x Gd 1-x Ca 4 O(BO 3 ) 3 (Nd x Gd 1-x COB) crystal was obtained by the CZ pulling method. The polarized transmittance spectrum was measured at room temperature on a 9 × 9 × 9 mm 3 Nd x Gd 1-x COB (x = 0.07) sample. The (66.8, 132.6) phase-matching direction was reported, firstly and its d eff is 2.1 pm/V which is similar as that of BBO crystal. A 3 × 3 × 10 mm 3 sample without antireflective coating was side-pumped by a pulsed dye-laser tuned to 595.4 nm. The green-light output energy was 1.35 mJ at the pump energy 17.5 mJ. The conversion efficiency is 7.7%, and the threshold energy is less than 1.2 mJ which are the best results up to now to our knowledge.