Injection-Seeded 500 Hz Repetition Rate High Peak Power Single-Frequency Nd:YAG Laser for Mid-Infrared Generation

We develop an injection-seeded single-frequency neodymium-doped yttrium aluminum garnet (Nd:YAG) laser with 500 Hz repetition rate and high peak power. The laser construction is designed as seed injection and master oscillator power amplifier (MOPA) including single-frequency master oscillator, extra-cavity frequency doubling crystal, and round-trip power amplifier. The master oscillator can emit 1,064 nm laser of 8.4 mJ with 6.8 ns pulse width at the pump energy equal to 23 mJ. A green laser energy of 1.1 mJ is obtained by setting the proper temperature of the LBO crystal. The pulse energy of 1,064 nm laser decreases to 6.5 mJ after passing through the LBO crystal and rises to 25.3 mJ after a round-trip power amplifier corresponding to the extraction efficiency of 29%. The final output pulse width is 6.5 ns, representing a peak power of 3.9 MW. The 1,064 nm laser beam quality factor M² of the master oscillator and the amplified one are 1.3 and 1.5, respectively. The laser will be used to generate mid-infrared where the 532 nm laser with narrow pulse width is to pump sheet optical parametric oscillator (OPO) and the 1,064 nm laser with high peak power to pump the OPO.     

A Novel 1,066 nm Nd:Gd<Subscript>0<Emphasis Type="Italic">.</Emphasis>69</Subscript>Y<Subscript>0<Emphasis Type="Italic">.</Emphasis>3</Subscript>NbO<Subscript>4</Subscript> Passively <Emphasis Type="Italic">Q</Emphasis>-Switched Pulse-Burst Laser

We demonstrate for the first time a Cr⁴⁺:YAG passively Q-switched 1066 nm pulse-burst laser under 879 nm direct pump with a novel Nd:Gd_0.69Y_0.3NbO₄ crystal. The output laser characteristics with different pump repetition rates and different Cr⁴⁺:YAG initial transmission are studied. Without the Cr⁴⁺:YAG, we obtain a maximum output energy of 2.55 mJ at an absorbed pump energy of 5.79 mJ with the highest 48% slope efficiency. The pulse-burst laser contains a maximum of 7 pulses for a Cr⁴⁺:YAG initial transmission of 55% and a pump repetition rate of 1 kHz. The single-pulse energy and narrowest pulse width reach 160 μJ and 5.5 ns at 38.2 kHz, with a peak power of 32 kW.     

Q-switched Ho:YAlO<Subscript>3</Subscript> laser pumped by Tm:YLF laser at room temperature

A Q-switched high efficient Ho:YAlO₃ (Ho:YAP) laser pumped by a diode-pumped Tm:YLF laser at room-temperature is realized. The maximum output energy reaches 1.58 mJ under the repetition frequency of 5 kHz, when the incident pump power is 15.6 W. The pulse width is 22 ns. The wavelength is 2118 nm when the transmission of output coupler is 30%. The beam quality factor is M ² ∼ 1.39 measured by the traveling knife-edge method.     

6.1 MW, 10 kHz Side-Pumped Burst-Mode Nd:YAG Laser

We present a compact high-peak-power, high-repetition-rate burst-mode laser from a master-oscillator power amplifier (MOPA) at 1064 nm for laser-based measurement applications. The oscillator is an 808 nm pulsed laser diode side-pumped acousto-optical (A-O) Q-switched Nd:YAG laser at repetition rates ranging from 10–100 kHz, producing a pulse train with a pulse number of 2–25. The maximum output energy of the oscillator is 15.6 mJ at 10 kHz, whereas it is 1.7 mJ at 100 kHz. After twostage amplifiers, a single-pulse energy of 85.2 mJ with a pulse-width of 14.5 ns is achieved at 10 kHz, which produces a peak power of 6.1 MW. At 100 kHz, the total burst energy reaches 220 mJ with a single-pulse energy of 8.8 mJ in the pulse burst laser system.     

High-peak-power,high-repetition-rate LD end-pumped Nd:YVO<Subscript>4</Subscript> burst mode laser

A compact high-peak-power, high-repetition-rate burst mode laser is achieved by an acousto-optical Q-switched Nd:YVO₄ 1064 nm laser directly pumped at 878.6 nm. Pulse trains with 10–100 pulses are obtained using acousto-optical Q-switch at repetition rates of 10–100 kHz under a pulsed pumping with a 1 ms duration. At the maximum pump energy of 108.5 mJ, the pulse energy of 10 kHz burst mode laser reaches 44 mJ corresponding to a single pulse energy of 4.4 mJ and an optical-to-optical efficiency of 40.5 %.The maximum peak power of ~468.1 kW at 10 kHz is obtained with a pulse width of 9.4 ns. The beam quality factor is measured to be M ² ~1.5 and the pulse jitter is estimated to be less than 1 % in both amplitude and time region.     

LD end pumped, actively mode locked and passively Q-switched Nd:YAP laser at 1341 nm

An end pumped Nd:YAP laser at 1341 nm is actively mode locked and passively Q-switched. Pumping was done with a pulsed high power laser diode with maximum power 425 W. V³⁺:YAG with 61% initial transmission served as saturable absorber, and an acousto-optic modulator is used for active mode locking. The output pulse train with 69 ns duration has a total energy of 3.2 mJ with ±4% shot-to-shot fluctuation. The peak output energy of a single mode locked pulse is 0.25 mJ. The pulse duration of a single mode locked pulse is less than 800 ps. The output laser beam is nearly diffraction limited with 1.6 mm diameter, and beam propagation factor M² about 1.3.     

Millijoule intracavity OPO driven by a passively Q-switched Nd:YVO<Subscript>4</Subscript> laser with AlGaInAs quantum-well saturable absorber

We originally demonstrate the use of an AlGaInAs periodic quantum-well absorber to achieve a quasi-continuous-wave (QCW) diode-pumped passively Q-switched Nd:YVO₄ laser with an intracavity optical parametric oscillator (OPO). With a diode-pumping energy of 35 mJ, the output pulse energy and the pulse width at 1573 nm are found to be 1.58 mJ and 26 ns, respectively. The pulse repetition rate can be up to 100 Hz with the overall OPO beam quality M² factor to be better than 1.5.     

885 nm LD end-pumped 22.7 W high beam quality electro-optical Q-switched Nd:YAG laser

We report an 885 nm laser diode (LD) end-pumped high beam quality (M _x ² = 1.322, M _y ² = 1.235) electro-optical Q-switched Nd:YAG laser with TEM₀₀-mode output for the first time. At the absorbed pump power of 59.5 W, a 22.7 W 1064 nm laser was achieved at 10 kHz repetition rate with optical-to-optical efficiency of 38.1%. The maximum pulse energy and shortest pulse width were 5.1 mJ and 14.5 ns at 2 kHz repetition rate, and the calculated peak power was 352 kW.     

A Compact YAG/Nd:YAG/Cr:YAG Passively <Emphasis Type="Italic">Q</Emphasis>-Switched Pulse Burst Laser Pumped by 885 nm Laser Diode

We demonstrate a high-repetition-rate, short-pulse-width pulse burst laser from a compact 885 nm laser diode directly pumped by a passively Q-switched YAG/Nd:YAG/Cr:YAG laser. We investigate the output laser characteristics with different output transmissions and spot sizes of the pumping laser and compare these characteristics. After optimization, we achieve a shortest pulse width of 1.4 ns generated by a 1,064 nm pulse burst laser. The single-pulse energy reaches 239 μJ at 86.3 kHz, with a peak power of 117.2 kW.     

High-Pulse-Energy Passively <Emphasis Type="Italic">Q</Emphasis>-Switched 1,123 nm Laser with a Nd:GdYAG Mixed Garnet as Laser Medium

We demonstrate a diode-pumped passively Q-switched Nd:GdYAG mixed garnet laser at 1,123 nm. A Cr⁴⁺:YAG crystal with an initial transmission of 97% is used as the saturable absorber. The maximum average output power is 1.05 W at an absorbed pumping power of 8.12 W. A single-pulse energy can reach up to 78.9 μJ, with a corresponding pulse repetition rate of 13.3 kHz.     

LD-pumped passively Q-switched Nd:GdVO<Subscript>4</Subscript> laser at 1342 nm with high initial transmission V:YAG saturable absorber

We have realized, for the first time to our knowledge, the passive Q-switching operation of an LD-pumped Nd:GdVO₄ laser at 1342 nm with V:YAG saturable absorber of initial transmission as high as 96%. This laser is investigated under different transmissions of the output coupler. The dependences of average output power, pulse width, pulse repetition rate, single-pulse energy and peak power on incident pump power are also measured. The shortest pulse width of 80 ns, the maximum single-pulse energy of 19.5 μJ and the highest peak power of 244 W are obtained with the output coupler of T = 15% and the pump power of 7.93 W. We find a special experimental phenomenon that the pulse repetition rate begins to drop after reaching the peak with the increase of the pump power. This phenomenon is analyzed and the theoretical calculations are consistent with the experimental results.     

Pulsed Nd:YAP laser at 1432 nm pumped with high power laser diode

LD end pumped Nd:YAP laser operation in the eye safe spectrum region at 1432 nm is reported. With pump energy of 256 mJ, maximum linearly polarized output of 26 mJ is obtained. The optical-to-optical overall efficiency is around 10%, and the slope efficiency is around 18%. The laser beam operates with spiking mode with a total emission period of less than 300 µs at 10 Hz. The stimulated emission cross section is estimated at around 0.85 × 10^− 20 cm².     

Three-level operation of a diode-bar-pumped Yb:S-FAP laser

We present an all solid-state Yb:S-FAP laser system running on the three-level laser transition at 985 nm. The pump source was a high fill-factor laser diode bar, with the output reformatted using a two-mirror beamshaping system to produce a rectangular pump beam that focused to a square spot. A nearly on-axis multipassing system was used to obtain four pump passes through a 1.6 mm Yb:S-FAP laser crystal. Gain-switched three-level laser output was achieved with an efficiency of 4.3% with respect to incident pump power. Electro-optic Q-switching produced 0.12 mJ pulses for a pump pulse energy of 11 mJ. Intra-cavity second-harmonic generation yielded a maximum pulse energy at 492.5 nm of 12 μJ.     

A Diode-Pumped Actively Q-Switched and Injection-Seeded Tm:LuAG Laser at Room Temperature

We elaborate a diode-end-pumped actively Q-switched injection-seeded Tm:LuAG laser. To achieve power scaling with good beam quality, we construct a more flexible laser with longer cavity accommodated strongly aberrated thermal lens in a Tm:LuAG laser and took special care in designing the laser resonator. Under Q-switched operation, we achieve a maximum output energy of 2.6 mJ with a pulse width of 318.2 ns at a pulse repetition frequency of 50 Hz. To control the spectral, temporal, and phase characteristics of the Tm:LuAG laser, the ring laser is injected by a seed laser, which provides a 50 mW single longitudinal-mode laser output at a wavelength of 2,022.6 nm. We achieve an output energy of 1.8 mJ with a pulse width of 293.0 ns after employing the injection seed.     

914 nm LD end-pumped 31.8 W high beam quality E-O Q-switched Nd:YVO4 laser without intracavity polarizer

We report a 914 nm LD end-pumped high power, high beam quality (M _x ² = 1.378, M _y ² = 1.287) electro-optical Q-switched Nd:YVO₄ laser with TEM₀₀-mode output. At the absorbed pump power of 67.6 W, a 31.8 W 1064 nm Q-switched laser with 43 ns pulse duration was achieved at 100 kHz repetition rate, corresponding to an optical-to-optical efficiency of 47%. The maximum pulse energy and shortest pulse width were 1.67 mJ and 18.5 ns at 10 kHz, and the calculated peak power was 90.3 kW. To the best of our knowledge, this is the highest Q-switched output power ever obtained for a Nd:YVO₄ oscillator pumped at 914 nm.     

High beam quality and compact diode end-pumped Nd:YVO<Subscript>4</Subscript> slab laser with a hybrid resonator

A compact, high power and high beam quality diode-end-pumped CW Nd:YVO₄ slab 1064 nm laser with a hybrid resonator is demonstrated. The maximum output power of 23.0 W is obtained under the pump power of 66.7 W, which gives the slope efficiency and optical conversion efficiency of 52.0 and 34.0%, respectively. The beam quality M² factors are measured to be 1.5 in the unstable direction and 1.7 in the stable direction. The power stability of the LD end-pumped slab laser at an output power of 19 W is measured to be 0.7% for half an hour operation.     

Intracavity sum-frequency generation of CW blue light in Nd:LuVO<Subscript>4</Subscript> laser

We report for the first time a continuous-wave (CW) blue laser emission by sum-frequency mixing in Nd:LuVO₄ crystal. Using type-I critical phase-matching (CPM) LBO crystal, a blue laser at 493 nm is obtained by 1066 and 916 nm intracavity sum-frequency mixing. The maximum laser output power of 520 mW is obtained when an incident pump laser of 18.2 W is used. At the output power level of 520 mW, the output stability is better than 2.8%. The beam quality M ² value is are about 1.22 and 1.31 in both horizontal and vertical dimensions respectively.     

A Single -Longitudinal-Mode Nd:Ce:YAG <Emphasis Type="Italic">Q</Emphasis>-Switched Laser Based on a Three-Plan Resonant Reflector

We present an efficient and compact passively Q-switched flash-lamp-pumped Nd:Ce:YAG singlelongitudinal-mode (SLM) laser system. With Cr⁴⁺:YAG as a saturable absorber, we design a three-plan resonant reflector for generating smooth SLM Q-switched pulses. We provide a theoretical calculation and optimization of the resonant reflector for improving the longitudinal-mode selection ability. We obtain a stable SLM output with a single-pulse energy of 10 mJ and a pulse width of 10.7 ns at 10 Hz. The near-diffraction-limited beam-quality parameter M² is less than 1.5. The system can operate with a repetition rate from 1 to 10 Hz. We achieve the stable laser operation with less than 3% fluctuation of the pulse energy within 10,000 shots.     

Diode-pumped long-pulse-width Tm:YAG laser at room temperature

We report the pulsed-diode-pumped and acoustics-optically Q-switched operation of a long-pulse-width Tm:YAG laser at room temperature. Output energy for single pulse of 48 mJ is obtained under the incident pump energy of 217.3 mJ, corresponding to a slope efficiency of 30.2% and an optical conversion efficiency of 22.1%. For the Q-switched regime, maximum pulse energy of 3.25 mJ and the pulse width of 232.8 ns at the repetition rate of 30 Hz are achieved. The wavelength of the Q-switched laser is 2.013 μm. A beam quality factor of M ² < 1.4 is measured using the traveling 90/10 knife-edge method.     

Simultaneous dual-wavelength oscillation at 1357 nm and 1444 nm in a Kr-flashlamp pumped Nd:YAG laser

A Nd:YAG laser pumped by a Kr-flashlamp with simultaneous dual-wavelength operation at 1357 nm (⁴F_3/2 → ⁴I_13/2(R₁ → X₄)) and 1444 nm (⁴F_3/2 → ⁴I_13/2(R₁ → X₇)) is demonstrated and its characteristics was analyzed. The output energy of 82 mJ at 1357 nm and 138 mJ at 1444 nm were achieved simultaneously with the maximum electrical input energy of 44 J. Stability of the output energy in the dual-wavelength operation was 1.41% at the maximum input energy of 44 J. However, the stabilities at each wavelength in the dual-wavelength operation showed much lower stability.