YAG Saturable Absorber Research Articles

High-radiance light sources with LED-pumped luminescent concentrators applied to pump Nd:YAG passively Q-switched laser

By power scaling of LEDs pump concentrators we demonstrated a visible light source (centered at 550nm) producing 294W with a radiance of 668W/cm2/sr in the air. Using more than 1100 LEDs, this setup represents one order of magnitude improvement in terms of output power and brightest of LED pump concentrator ever reported.We pushed further the concept of low cost high brightness light source using this concentrator to pump a very simple Nd:YAG laser in free running mode and in passively Q-switched regime using a Cr:YAG saturable absorber. Output energies up to 263µJ with a pulse duration of 33ns have been obtained at 1064nm, leading to a peak power of 8kW in a TEM00 mode.

Laser characteristics of Nd3+-doped calcium barium niobate ferroelectric crystal at 1.06 and 1.34 μm.

We report on diode-pumped Nd3+-doped calcium barium niobate ferroelectric crystal (Nd:CBN-28) lasers at 1.06 and 1.34μm. The maximum output power of the 1.06μm laser reaches 0.69W in the continuous-wave regime, which is believed to be the highest output power with Nd:CBN-28 crystal to date. Using a chopper to modulate the pump, the highest output power further improves to 0.77W. Passively Q-switched laser operation at 1.06μm, using a Cr:YAG saturable absorber, is realized with a maximum average output power of 89mW, a pulse width of 220ns, and a pulse energy 10.8μJ. A quasi-continuous-wave laser at 1.34μm with a chopper is also demonstrated with maximum output power of 56mW. The scaled output power in the fundamental wave should be favorable for the investigation on broadband nonlinear self-frequency conversion into visible.

Passively Q-switched oscillation at 1005–1012 nm of a miniature Yb:LuPO4 crystal rod laser

A diode pumped Yb:LuPO4 miniature crystal rod laser operating at wavelengths of 1005.0–1012.5 nm, which was passively Q-switched with a Cr4+:YAG saturable absorber, was demonstrated. An average output power of 7.2 W at 1012.5 nm was generated at a pulse repetition rate of 166.7 kHz, with optical-to-optical and slope efficiencies being 38.5% and 45%, respectively. Under conditions of higher output coupling and lower initial transmission of the saturable absorber, an output power of 2.9 W at wavelengths around 1005.0 nm could be reached at 19.2 kHz, the resulting pulse energy, duration and peak power were respectively 151 µJ, 3.0 ns and 50.3 kW.

Simultaneous dual-wavelength Q-switched Nd:YAG laser at 1052 and 1073 nm.

We report a continuous-wave dual-wavelength Nd:YAG laser at 1052 and 1073 nm, for the first time to the best of our knowledge, in free-running mode. The maximum output power reaches 6.64 W with slope efficiency of about 42.1% with respect to the absorbed power. Inserting a Cr:YAG saturable absorber, the dual-wavelength laser can operate in the Q-switching regime with maximum average output power of 880 mW. The minimum pulse width and the highest pulse repetition rate are 28 ns and 17.12 kHz, respectively. The dual-wavelength laser has potential to generate a 5.7 THz wave via the difference-frequency method.

Experimental and theoretical study on an intracavity KTiOPO4 optical parametric oscillator pumped by a dual loss modulated Q-switched and mode-locked laser

In this paper, a sub-nanosecond KTiOPO4 (KTP)-based intracavity optical parametric oscillator (IOPO) pumped by a dual-loss modulated Q-switched and mode-locked (QML) laser with an acousto-optic modulator (AOM) and a Cr4+:YAG saturable absorber (Cr4+:YAG-SA) has been demonstrated. By changing the initial transmission of Cr4+:YAG-SA and the transmission of the output coupler at the signal wavelength, the signal pulse width compression can be realized. At an incident pump power of 8.3W and an AOM repetition rate of 15kHz, a single signal pulse underneath Q-switched envelope with the shortest pulse width of 220ps was obtained. The experimental results reveal that this is a simple and effective way to obtain the sub-nanosecond OPO signal pulses. In addition, the related coupled rate equations have been set up and the simulation results agreed with the experimental results well.

Characterisation and Modelling of a Passively Q-switched Yb:CaF2 Laser

A diode-pumped, passively Q-switched Yb:CaF2 laser with Cr:YAG saturable absorber has been developed and characterized. A maximum average output power of 737 mW at a repetition rate of 1060 Hz was obtained with slope efficiency of 20%. The output pulse energy was 0.7 mJ with a pulse width of 78 ns giving a peak pulse power of 8.9 kW with a very high beam quality. Laser threshold pump power was 8.6 W. Rate equation modeling was also performed for the Q-switched Yb:CaF2 laser and the output characteristics shown generally matched experimental values and trends observed.

Modulation frequency characteristics in a doubly Q-switched Nd:Gd0.63Y0.37VO4 laser with an acousto-optic modulator and a V3+:YAG saturable absorber

A doubly Q-switched Nd:Gd0.63Y0.37VO4 laser emitting 1342 nm wavelength with an acousto-optic modulator and a V3+:YAG saturable absorber is presented and its modulation frequency characteristics are studied. The experimental results show that the periodic ramping behavior of the modulation frequency in this system exists. The points of inflection are related to pump power. The average output power, the pulse width and the peak power are related to the modulation frequency. Numerical simulations based on the coupled rate equations are given to analyze and verify the experimental results.

High-power and high-efficiency diode-pumped Nd:LuYAG mixed crystal lasers operating at 939 and 946 nm.

We report on high-performance infrared lasers at 0.94μm based on quasi-three-level transition of F3/24→I9/24 in Nd:LuYAG mixed crystal, for the first time to our knowledge. The maximum output power was achieved to 5.64W with slope efficiency of approximately 52.5% at 946nm. The simultaneous dual-wavelength laser at 939 and 946nm is also obtained with maximum output power of 3.61W and slope efficiency of 34.8% by introducing a glass etalon into the cavity. Moreover, a 2.0-W single-wavelength laser at 939nm can be further attained by suitably tilting the etalon. Using a Cr:YAG saturable absorber, Q-switched laser operation is realized with maximum average output power of 0.68W and the narrowest pulse width of 8.4ns, which results in the maximum single pulse energy of approximately 55.3μJ and the maximum pulse peak power of approximately 6.15kW. Finally, thermal focal length of the laser crystal is estimated by using a flat-flat laser cavity.

Passively Q-switched Nd:GYSGG laser operating at 1.3 μm with V:YAG as saturable absorber

The performance of a laser diode-pumped passively Q-switched Nd: GYSGG laser at 1331nm with a V: YAG saturable absorber was first reported. A maximum average output power of 251mW was obtained under pump power of 11.75W. By using 8.8% output coupler, a minimum pulse width of 23.9ns and a pulse repetition rate of 11kHz were achieved, corresponding to the peak power of 954W.

50-kHz, 50-ns UV pulse generation by diode-pumped frequency doubling Pr3+:YLF Q-switch laser with a Cr4+:YAG saturable absorber.

We demonstrate intracavity second-harmonic generation at 320 nm of a diode-pumped praseodymium-doped YLF laser Q-switched by a Cr4+:YAG crystal. By employing two 3.5-W high-power blue InGaN diode lasers as the pump source, we obtained 50-ns Q-switched pulses with a pulse energy of 1.54 μJ at a repetition rate of 50 kHz. A rate equation analysis shows good agreement with the experimental results.

Sub-nanosecond Yb:KLu(WO4)2 microchip laser.

A diode-pumped Yb:KLu(WO4)2 microchip laser passively Q-switched by a Cr4+:YAG saturable absorber generated a maximum average output power of 590 mW at 1031 nm with a slope efficiency of 55%. The pulse characteristics were 690 ps/47.6 μJ at a pulse repetition frequency of 12.4 kHz. The output beam had an excellent circular profile with M2<1.05. Yb:KLu(WO4)2 is very promising for ultrathin sub-ns microchip lasers.

Simultaneous dual-wavelength pulses achieved by mixing spiking and passive Q-switching in a pulsed Nd:GdVO4 laser with a Cr4+:YAG saturable absorber.

A method for generating a dual-wavelength, dual pulse Nd:GdVO4 laser at 1.06 μm (F3/24→I11/24) and 1.34 μm (F3/24→I13/24) is proposed. When the 1.34-μm spiking threshold is less than the 1.06-μm Q-switched threshold, the generation of a 1.34-μm spiking pulse leads to a 1.06 μm Q-switched pulse, resulting in a dual-wavelength laser. With a pump power of 11 W, the pulse widths are 89.5 and 427.8 ns for 1.06 and 1.34 μm, respectively, with a 36.5-KHz repetition frequency.

Direct Measurement of Temporal Transmission Distribution of a Saturable Absorber in a Passively Q-Switched Laser

An in situ temporal decay and spatial distribution of the transmission of a Cr 4+ :YAG saturable absorber in a passively Q-switched Nd:YAG laser were measured simultaneously by a scanning transmission focused laser beam method. An excited ion decay time of 4 μs and a top hat (saturated) transmission distribution were clearly observed. The ratio of the ground-state absorption cross section and the excited-state absorption cross section (σ SAπ /σ ESAπ ) for π-polarized light to the S 4 local symmetry axis of Cr 4+ center was measured at approximately 4.1-4.2. Using a theoretical fitting of the transmission distributions, we found the ground-state absorption cross sections to be at 1 × 10 -17 and 2.3 × 10 -19 cm 2 for π and for σ-polarized light to the S 4 local symmetry axis of Cr 4+ center, respectively. The value of the excited-state absorption cross section was also estimated correspond to 2.4 × 10 -18 cm 2 .

Giant-pulse Nd:YVO_4 microchip laser with MW-level peak power by emission cross-sectional control

We present a giant-pulse generation laser realized by the emission cross-section control of a gain medium in a passively Q-switched Nd:YVO4 microchip laser with a Cr4+:YAG saturable absorber. Up to 1.17 MW peak power and 1.03 mJ pulse energy were obtained with a 100 Hz repetition rate. By combining the Nd:YVO4 crystal with a Sapphire plate, lower temperature difference between a pump region in the gain crystal and a crystal holder was obtained which helped to keep the cavity in stability zone at elevated temperatures and allowed the achievement of the high peak power for this laser system.

Multi-wavelength passively Q-switched c-cut Nd:YVO4 self-Raman laser with Cr4+:YAG saturable absorber

A multi-wavelength passively Q-switched self-Raman laser with a c-cut Nd:YVO4 both as laser and Raman medium is reported. With the increasing pump power, the multi-wavelength laser including the fundamental line at 1067.4nm, 1st-Stokes at 1097.9nm, 2nd-Stokes at 1130.1nm, and 3rd-Stokes at 1163.6nm is generated sequentially. At a pump power of 5.0W, the maximum output power of the four discrete lines are 186.8mW, 246.5mW, 158.4mW and 63.6mW, with corresponding optical conversion efficiencies of 3.7%, 4.9%, 3.2% and 1.3% respectively. The total stimulated Raman scattering conversion efficiency is 9.4%. To our best knowledge, this is the first report of the 2nd-Stokes at 1130.1nm and 3rd-Stokes at 1163.6nm.

High-Power Passively Q-Switched Nd:YAG Laser at 1112 nm with a Cr4+:YAG Saturable Absorber**Supported by the Natural Science Foundation of Shandong Province under Grant Nos ZR2015FM018 and ZR2014FM028, and the National Natural Science Foundation of China under Grant No 61475086.

A high-power passively Q-switched Nd:YAG laser operating at 1112 nm with Cr4+:YAG as a saturable absorber is demonstrated. Under 808 nm diode-direct pumping, the maximum average output power of 2.73 W is achieved at the pump power of 16.65 W, corresponding to an optical-to-optical conversion efficiency of 16.4%. At the same time, the pulse width, pulse repetition rate, single pulse energy and peak power are 27.2 ns, 9 kHz, 303.3 μJ and 11.2 kW, respectively. As far as we know, the result gives the highest average output power at 1112 nm generated by an 808 nm diode-end-pumped Nd:YAG laser.

Watt-Level Output Power Operation From Diode-Laser Pumped Circular Buried Depressed-Cladding Waveguides Inscribed in Nd:YAG by Direct Femtosecond-Laser Writing

Circular buried depressed-cladding waveguides have been inscribed in Nd:YAG ceramic media by direct writing with a femtosecond-laser beam. A classical step-by-step translation of the medium method, as well as a newly developed helical-moving technique, were employed to fabricate waveguides with 100- $\mu\mbox{m}$ diameter. Laser emission has been obtained under the pump with a fiber-coupled diode laser. Continuous-wave output power of 3.1 W at 1.06 $\mu\mbox{m}$ and 1.6 W at 1.3 $\mu\mbox{m}$ were achieved from a waveguide inscribed by helical movement in a 4.5-mm-long 1.1-at.% Nd:YAG; the overall optical-to-optical efficiency with respect to the absorbed pump power was 0.31 at 1.06 $\mu\mbox{m}$ and 0.17 at 1.3 $\mu\mbox{m}$ . Q-switch operation has been realized with Cr 4+:YAG saturable absorber crystal. Using Cr 4+:YAG with initial transmission of 0.90, an average output power of 680 mW has been measured from a waveguide that was written by the classical method in a 7.7-mm-long 1.1-at.% Nd:YAG ceramic. The laser pulse energy was 19.7 $\mu\mbox{J}$ , and the pulse peak power reached 7 kW.

High-power continuous-wave and high-energy Q-switched miniature Yb:Y3Ga5O12 crystal lasers

We report on the continuous-wave (CW) and passive Q-switching performance of a miniature Yb:Y3Ga5O12 crystal laser end pumped by a 935-nm diode laser. A maximum CW output power of 12.03 W is produced with an optical-to-optical efficiency of 54.4%, while the slope efficiency is 63%. In the passively Q-switched operation achieved with a Cr4+:YAG saturable absorber, an average output power of 2.12 W at 1025.2 nm is generated with a slope efficiency of 46% at a pulse repetition rate of 5.0 kHz. The pulse’s energy, duration, and peak power are 424 μJ, 2.3 ns, and 184.3 kW, respectively.

Modulation frequency characteristics of the Q-switched envelope in a doubly Q-switched and mode-locked laser with acousto-optic modulator and Cr4+:YAG saturable absorber

The modulation frequency characteristics of the Q-switched envelope in a doubly Q-switched and mode-locked Nd:GGG laser with an acousto-optic modulator (AOM) and Cr 4+ :YAG saturable absorber are given. At a fixed incident pump power, the repetition rates of the Q-switched envelope and the related laser characteristics versus the modulation frequency of AOM for different small signal transmissions of Cr 4+ :YAG saturable absorbers have been measured. The experimental results show that the repetition rates of the Q-switched envelope, the average output power, the average peak power, and the pulse widths of the Q-switched envelopes are subharmonics of the modulation frequency at a fixed incident pump power. Furthermore, the mechanism for these behaviors is discussed.

Passively Q-switched Nd:YAG ceramic laser with V(3+):YAG saturable absorber at 1357 nm.

1357 nm single-wavelength continuous-wave and passively V(3+):YAGQ-switched Nd:YAG ceramic crystal lasers have been experimentally demonstrated for the first time to our knowledge. The output power of the continuous-wave laser was as high as 2.4 W under the incident pump power of 14.8 W. The corresponding optical to optical efficiency was about 16.2% and the slope efficiency was about 18.6%. The Q-switched laser remained single-wavelength output with a maximum average output power of 628 mW at the incident pump power of 12.4 W. The corresponding pulse width was 21 ns and the repetition frequency was 15 kHz.