YAG Saturable Absorber Research Articles

High-order Stokes generation in a KTP Raman laser pumped by a passively Q-switched ND:YLF laser

High-order Stokes wave was observed in an x-cut KTP crystal based on stimulated Raman scattering (SRS) pumped by a passively Q-switched Nd:YLF laser with a Cr4+:YAG saturable absorber. Output spectra including the fundamental wave at 1047nm and six Stokes wavelengths at 1077nm, 1110nm, 1130nm, 1143nm, 1164nm, 1180nm based on two Raman frequency shift at 267.4cm−1 and 693.0cm−1 were obtained simultaneously. We also detected green light generation with output power of 12mW from self frequency mixing in the KTP crystal. The maximum total output power reached 452mW at the repetition frequency of 8.1kHz, corresponding to the optical-to-optical conversion efficiency of 4.61% and pump-to-Raman conversion efficiency of 3.6%.

Generation of low repetition rate subnanosecond pulse in an optimal doubly QML Nd:Lu0.15Y0.85VO4 laser with EO and Cr⁴⁺:YAG.

Employing different output couplers and Cr4+:YAG saturable absorbers with different initial transmittances in a Q-switched mode-locked (QML) Nd:Lu0.15Y0.85VO4 laser, the symmetry of the Q-switched envelope was optimized and the envelope duration was shortened. By applying the above mentioned optimization into an EO/Cr4+:YAG dual-loss-modulated QML Nd:Lu0.15Y0.85VO4 laser, the Q-switched envelope can be further compressed until only containing one mode-locking pulse. Mode-locking pulse energy and peak power up to 1.15 mJ and 3.15 MW, respectively, were achieved. The rate equation theory was utilized to analyze the experimental results, and the theoretical simulation was basically in accordance with the experimental data.

Saturation of 640-nm absorption in Cr⁴⁺:YAG for an InGaN laser diode pumped passively Q-switched Pr³⁺:YLF laser.

We measure the absorption recovery time, the ground- and excited-state absorption cross sections of a Cr4+:YAG crystal at 640 nm for the first time. A pump-probe measurement reveals the existence of two recovery times of 26 ns and 5.6 μs. By a Z-scan experiment, the ground- and excited-state absorption cross sections are estimated to be 1.70 - 1.75 × 10(-17) and 0.95 - 1.00 × 10(-17)cm2, respectively. The adequacy of the proposed model and the accuracy of the estimated parameters of the saturable absorber are verified by reproducing the experimentally obtained performance of a passively Q-switched Pr3+:YLF laser with the Cr4+:YAG saturable absorber from rate equation analysis.

Holographic self-Q-switching of Nd:YAG all-solid-state lasers with Cr:YAG saturable absorber

The study of the generation characteristics of Nd:YAG lasers with multiloop self-organizing phase conjugate cavities using a passive Q-switch based on a Cr:YAG crystal is carried out. It is shown that Q-switching of the phase conjugate cavity is caused not only by absorption saturation of the passive Q-switch, but also by modulation of diffraction efficiency of holographic saturable gain gratings in the Nd:YAG active laser medium.

High-repetition-rate Q-modulation in solid-state laser using fast saturable absorber V:YAG

A high-repetition-rate Q-modulation operation in a solid-state Nd:GdVO4 laser with a V3+:YAG saturable absorber has been demonstrated in this paper. The V3+:YAG crystal behaves as a fast saturable absorber in this laser because of its very short lifetime of 22 ns. Taking advantage of such fast bleaching recovery and effective cooling of the V:YAG by a home-made copper holder, we realized a pulse repetition rate of 2.4 MHz, which is, to our best knowledge, the maximum among the reported passively Q-switched lasers. The corresponding average output power and pulse width were 1.28 W and 170 ns, respectively, giving a slope efficiency of 15.9% and a pulse energy of 0.53 µJ. This compact high-repetition-rate Q-switched laser offers a potential application in the construction of low-cost, integrated and portable sensing detection equipment which needs a high laser pulse repetition rate.

Stable Q-Switched Yb:NaY(WO4)2 Laser with Cr4+:YAG Saturable Absorber**Supported by the National Natural Science Foundation of China under Grant No 61405171, the Natural Science Foundation of Shandong Province under Grant No ZR2012FQ014, and the Science and Technology Program of the Shandong Higher Education Institutions of China under Grant No J13LJ05.

The passively Q-switched Yb:NaY(WO4)2 (Yb:NaYW) laser is studied. By using Cr4+:YAG as the saturable absorber, a very stable pulse train is obtained. At a high pump power, the pulse to pulse timing jitter is measured to be less than 2% and the amplitude fluctuation is less than 4%. A Q-switched average output power of 2.3 W at 1029 nm is generated with a slope efficiency of 33.9%; the one-dimensional intensity distribution of the laser facula is of the Gaussian type. The output repetition rate, pulse energy, pulse width and peak power are 33.3 kHz, 70 μJ, 36 ns and 2.0 kW, respectively. The passively Q-switched process is simulated by solving the rate equations, the simulated results are in good agreement with the experimental data.

Diode-side-pumped, passively Q-switched Yb:LuAG laser

A high-gain, diode-side-pumped Yb:LuAG slab laser was designed and investigated for use at room temperature. Pumping occurred from a fast-axis collimated 2D laser diode stack emitting at a wavelength of 970 nm, with 0.8 J over a duration of 0.8 ms. The pump scheme, which enabled efficient mode matching and high gain, was analysed and experimentally verified for different dopant levels. An energy of 100 mJ with 23% slope efficiency in a near fundamental mode was achieved in the free-running regime. A peak power of 2.5 MW and a pulse energy of 10.1 mJ were demonstrated in passive Q-switching by means of a Cr:YAG saturable absorber with 39% initial transmission. The study defined the indications for optimizing such a system.

Experimental and theoretical study of a passively Q-switched Nd:LuAG laser at 13 μm with a V^3+:YAG saturable absorber

We report the characteristics of a diode-pumped continuous-wave (CW) and passively Q-switched Nd:LuAG laser emitting 1.3 μm wavelength. A maximum average output power of 954 mW was obtained under CW operation, giving a slope efficiency of 14.7%. With an V3+:YAG crystal wafer employed as saturable absorber, the passively Q-switched Nd:LuAG laser produced a minimum pulse duration of 17 ns under a repetition rate of 8 kHz, and a maximum single pulse energy of 18.9 μJ. A rate equation model is introduced to theoretically analyze the results obtained in the experiment, in which the Gaussian spatial distribution of the intracavity photon density and the longitudinal distribution of the photon density along the cavity axis are taken into account. The results of numerical calculations of the rate equations are consistent with the experimental results. The results indicated the Nd:LuAG crystal as a promising gain medium for achieving short pulses with high energy at 1.3 μm.

Diode-end-pumped passively Q-switched Nd:YAG crystal laser with V:YAG saturable absorber at 1319 and 1338 nm

A diode-end-pumped passively Q-switched Nd:YAG laser with a V:YAG saturable absorber emitting at 1319 and 1338 nm was demonstrated for the first time. A maximum output power of 286 mW was obtained with minimum pulse duration of 13.2 ns and the highest repetition rate was 15 kHz under an incident pump power of 7.7 W. The calculated highest peak power and pulse energy were 2.1 kW and 29 μJ, respectively.

Diode-pumped Nd:Gd3Ga5O12–KTiOPO4 green laser doubly passively Q-switched mode-locked by GaAs and Cr4+:YAG saturable absorbers

By simultaneously employing GaAs and Cr4+:YAG saturable absorbers, a diode-pumped doubly passively Q-switched and mode-locked (DP-QML) Nd:Gd3Ga5O12 (Nd:GGG)/KTiOPO4 (KTP) green laser has been presented. At the maximum incident pump power of 7.69 W, the obtained average output power, the pulse duration of the Q-switched envelope, the mode-locked pulse width and the pulse repetition rate are 62 mW, 16.8 ns, 352 ps, and 15.5 kHz, respectively, corresponding to a pulse energy of 4.2 µJ and a peak power of 0.25 kW. In comparison with singly passively Q-switched and mode-locked (SP-QML) green laser with GaAs or Cr4+:YAG saturable absorbers, the DP-QML green laser can generate shorter pulse width, deeper modulation depth and higher peak power. The coupled equations for diode-pumped doubly passively QML Nd:GGG/KTP green laser are given and the numerical simulations are in good agreement with the experimental results.

Diode-Side-Pumped Passively Q-Switched Nd:YAP Laser Operating at 1.34 μm with V3+:YAG Saturable Absorber

To the best of our knowledge, we have demonstrated, for the first time, a diode-side-pumped passively-Q-switched Nd:YAP laser operating at 1.34 μm with V3+:YAG used as a saturated absorber. In the passively Q-switched regime, we reached the highest output power of 7.52 W, the shortest pulse width of 197 ns, the largest pulse energy of 1.36 mJ, and the highest peak power of 6.93 kW with a V3+:YAG crystal used as the saturated absorber.

Simple Nd:YAG laser generates vector and vortex beam

We report a simple Nd:YAG laser that emits radially polarized beam with helical wavefront. The laser cavity consists of a piece of laser crystal and a plane output coupler, and there is no additional polarization component inside it. The pump light is converted into annular profile through de-focal coupling into a multi-mode fiber. For the continuous-wave (CW) operation, the laser emits radially polarized vortex beam, and it is observed that the helical wavefront of the laser beam is switched from right handedness to left handedness when the output coupler is tilted slightly. For the Q-switched operation under the insertion of a Cr4+:YAG saturable absorber inside the cavity, we obtain radially polarized outputs with left-handedness helical wavefront. By tilting the laser crystal slightly, the laser output switches to azimuthal polarization at pump power larger than 4.5 W and left-handedness helical wavefront of laser beam is preserved.

Scaling and passively Q-switch operation of a Nd:YAG laser pumped laterally through a YAG prism

Abstract We report on scaling of a laser configuration in which a YAG prism is used to couple the pump beam from a fiber-coupled diode laser directly into a Nd:YAG medium. Several resonator geometries have been investigated. In free generation regime laser pulses at 1.06 μm with energy of 22.1 mJ for the pump energy of 44.6 mJ were obtained from a 10.0 mm long, 1.0-at% Nd:YAG single crystal that had the high-reflectivity mirror coated directly on one of the laser crystal surface. The slope efficiency was 0.51. A similar uncoated Nd:YAG crystal placed in a plane–plane resonator delivered laser pulses with 17.8 mJ energy under the pump with 45.4 mJ energy, at 0.40 slope efficiency. Further, a passively Q-switched Nd:YAG/Cr 4+ :YAG composite ceramic laser pumped through a YAG prism has been built. Using a Cr 4+ :YAG saturable absorber of 0.85 initial transmission the device delivered laser pulses with 0.29 mJ energy and 11 ns duration. The output performances are compared to those obtained in a classical end-pumping scheme.

Variable energy, high peak power, passive Q-switching diode end-pumped Yb:LuAG laser

A new method to control the pulse energy in a passively Q-switched laser was proposed and experimentally verified for a diode-end-pumped Yb:LuAG laser. By changing the pumping area parameters it was possible to demonstrate generation of a wide range of output energies with a single laser configuration consisting of a gain medium, passive Q-switch and out-coupling mirror. The range of available energies 0.15–0.51 mJ with maximum peak power of 113 kW in simple Q-switching regime by means of a Cr:YAG saturable absorber and a Yb:LuAG gain medium pumped by a 20 W laser diode emitting at 968 nm was demonstrated.

Intracavity KTP-based OPO pumped by a dual-loss modulated, simultaneously Q-switched and mode-locked Nd:GGG laser.

An intracavity KTiOPO(4) (KTP) optical parametric oscillator (OPO) pumped by a simultaneously Q-switched and mode-locked (QML) Nd:Gd(3)Ga(5)O(12) (Nd:GGG) laser with an acousto-optic modulator (AOM) and a Cr(4+):YAG saturable absorber is presented. A minimum mode-locking pulse duration underneath the Q-switched envelope was evaluated to be about 290 ps. A maximum QML output power of 82 mW at the signal wavelength of 1570 nm was achieved, corresponding to a maximum mode-locked pulse energy of about 5.12 μJ. The M(2) values were measured to be about 1.3 and 1.5 for tangential and sagittal directions using knife-edge technique.

Comparison of passively Q-switched laser performance of two composite Nd:YVO $$_{4}$$ 4 /Nd:YVO $$_{4}$$ 4 /Nd:YVO $$_{4}$$ 4 crystals with Cr $$^{4+}$$ 4 + :YAG saturable absorber

The passively Q-switched Nd:YVO $$_{4}$$ /Nd:YVO $$_{4}$$ /Nd:YVO $$_{4 }$$ 1.06- $$\upmu $$ m laser has been demonstrated by using Cr $$^{4+}$$ :YAG as saturable absorber. The characteristics are compared under different Nd-doped concentrations of laser crystals and different initial transmissions (T $$_0 )$$ of saturable absorbers. With an incident pump power of 6.52 W, the composite Nd(0.1 at.%):YVO $$_{4}$$ /Nd(0.5 at.%):YVO $$_{4}$$ /Nd(1.0 at.%):YVO $$_{4}$$ laser obtained the maximum average output power of 932 mW and the largest single pulse energy of 5.1 $$\upmu $$ J when T $$_0 =88$$ %. The shortest pulse width of 25 ns and the highest peak power of 177.4 W were achieved with T $$_0 =79$$ % for the composite Nd(0.1 at.%):YVO $$_{4}$$ / Nd(0.3 at.%):YVO $$_{4}$$ /Nd(0.8 at.%):YVO $$_{4}$$ crystal.

Role of modulation frequency in a hybrid Q-switched Nd:LuVO₄ laser with an acousto-optic modulator and a Cr⁴⁺:YAG saturable absorber.

This study presents a hybrid Q-switched Nd:LuVO₄ laser with an acousto-optic modulator (AOM) and a Cr⁴⁺:YAG saturable absorber. The importance of the modulation frequency of the AOM in this dual-loss modulation system is examined with two distinct observations: (1) the periodic-ramp pulse characteristics with the modulation frequency, and (2) the existence of the intrinsic modulation frequency for minimizing the pulsewidth. The shortest pulsewidth and the highest peak power were 10.6 ns and 13.9 kW, respectively, at a pump power of 10 W. Compared with the passively Q-switched laser, which has a pulsewidth of 18.3 ns, the ratio of pulse compression reaches 42%. Finally, numerical simulations based on the rate equations are used to verify the experimental results.

2 × 2 arrayed and passively Q-switched Nd:YVO4 laser under Dammann-arrayed pumping.

We reported our proof-of-concept investigation in developing an arrayed and passively Q-switched Nd:YVO4 laser. In the investigation, we used a Dammann grating to diffract the pumping light from a 808 nm laser diode into 2×2 pump beam array, and then used this pump array to pump a monolithic Nd:YVO4 laser crystal standing with a Cr4+:YAG saturable absorber inside a simple plano-plano resonator. As a result, 2×2 arrayed and nanosecond laser pulses were emitted. The laser-diode-pumped monolithic solid-state laser incorporated with a Dammann grating is promising for application in high-peak-power and multipoint pulse ignition of an automobile engine.

A high-peak-power passively Q-switched composite variable-cut vanadate laser

We present laser sources based on a novel method of controlling spectral parameters in diode-pumped vanadate lasers. Angular dependences of the luminescence intensity of Stark transitions at the 4F3/2‒4I11/2 transition in vanadate crystals are investigated. The operation of diode-pumped passively Q-switched composite variable-cut (θ = var, φ = 0) YVO4–Nd3+ : YVO4 lasers with Cr4+ : YAG saturable absorber is demonstrated (the narrowest pulse of 2 ns with the highest peak power of 24.3 kW). In the experiment, an efficient self-Raman laser was realized, based on the multifunctional variable-cut (θ = 25°, φ = 0) YVO4–Nd3+ : YVO4 laser crystal with the passive Q-switched.

Output Characteristics of a Diode-pumped Passively Q-switched Intracavity Frequency-doubled Nd:GdVO$_4$/LBO Red Laser with a V$^{3+}$:YAG Saturable Absorber

Output Characteristics of a Diode-pumped Passively Q-switched Intracavity Frequency-doubled Nd:GdVO$_4$/LBO Red Laser with a V$^{3+}$:YAG Saturable Absorber