Directly diode-pumped high-energy Ho:YAG oscillator

We report on the high-energy laser operation of an Ho:YAG oscillator resonantly pumped by a GaSb-based laser diode stack at 1.9 μm. The output energy was extracted from a compact plano-concave acousto-optically Q-switched resonator optimized for low repetition rates. Operating at 100 Hz, pulse energies exceeding 30 mJ at a wavelength of 2.09 μm were obtained. The corresponding pulse duration at the highest pump power was 100 ns, leading to a maximum peak power above 300 kW. Different pulse repetition rates and output coupling transmissions of the Ho:YAG resonator were studied. In addition, intracavity laser-induced damage threshold measurements are discussed.     

Single-frequency, injection-seeded Q-switched operation of a resonantly pumped Ho:YAlO3 laser at 2,118 nm

A 1.91 μm-pumped, injection-seeded 2,118 nm Q-switched Ho:YAlO₃ laser was demonstrated in this paper. Single-frequency and nearly transform-limited operation of Q-switched Ho:YAlO₃ laser was achieved by injection-seeded. The single-frequency Q-switched Ho:YAlO₃ laser output energy of 8 mJ at 100 Hz with a pulse width of 151 ns was obtained. The half-width of pulse spectrum measured by a heterodyne technique was 3.7 MHz.     

Efficient single-axial-mode operation of a Ho:YAG ring laser pumped by a Tm-doped silica fiber laser

Efficient single-frequency operation of a Ho:YAG ring laser at room temperature with a traveling-wave TeO2 acousto-optic modulator to enforce unidirectional operation is reported. By use of a 2-at. % Ho3+-doped 10-mm-long Ho:YAG rod, end pumped by a cladding-pumped tunable Tm-doped silica fiber operating at 1.9 microm, the Ho:YAG ring laser yielded 3.7 W of single-frequency output at 2.1 microm in a diffraction-limited TEM00 beam with M2 < 1.1 for an incident pump power of 8.8 W. The rf power required for unidirectional operation was 0.3 W and corresponded to an increase in cavity loss for the lasing direction (due to diffraction) of only 0.5%. The prospects for further improvement in efficiency are discussed.     

Ho:YAG laser intracavity pumped by a diode-pumped Tm:YLF laser

We report a compact Ho:YAG laser that is intracavity pumped by a diode-pumped Tm:YLF laser. Both lasers exhibit pulse mode behavior. Operating both crystals at room temperature (25 degrees C), we obtained 1.6 W of average output at 2.09 microm from the Ho:YAG laser for 15.4 W of diode power incident upon the Tm:YLF rod and a slope efficiency of 21%.     

Graphene passively Q-switched Ho:YAG ceramic laser

We report on the first graphene passively Q-switched Ho:YAG ceramic laser with central wavelength of 2,097 nm. Stable pulses of 28–64 kHz repetition rate and 2.6–9 μs pulse widths were generated under 1,907 nm thulium fiber laser pumping. Maximum average power of 264 mW with 9.3 μJ pulse energy was obtained under 3.27 W of pump power.     

520 mJ langasite electro-optically Q-switched Cr, Tm, Ho:YAG laser

A flash lamp pumped 2.09 μm Cr, Tm, Ho:YAG laser utilizing a self-grown La(3)Ga(5)SiO(14) crystal as the electro-optic Q-switch generator is proposed and demonstrated for the first time. Operating at 3 Hz repetition rate, 520 mJ pulse energy with 35 ns pulse width is achieved by optimizing the Q-switch delay time and compensating for the thermal depolarization with a quarter-wave plate. The corresponding peak power is 14.86 MW, and the Q-switched-to-normal-mode energy extraction efficiency is 66.3%. To our knowledge, this Q-switched giant pulse is the best result reported to date in 2.09 μm laser resonator.     

Single-frequency operation of a laser diode side-pumped Q-switched Tm:YAG laser using seeding injection technique

A laser diode (LD) side-pumped 2 μm single-frequency Q-switched Tm:YAG laser was demonstrated. The laser was injection seeded by a CW single frequency Tm:YAG laser with a twisted-mode cavity. The maximum single-frequency pulse energy was 16.3 mJ, with a pulse width of 570 ns and a pulse repetition rate of 10 Hz. The linewidth of the 2 μm single-frequency Q-switched laser was 0.68 MHz, measured by using the optical heterodyne technique. The M ² of the laser beam was measured to be 1.09 and 1.03 for x direction and y direction, respectively.     

2-W Ho:YAG laser intracavity pumped by a diode-pumped Tm:YAG laser

Efficient room-temperature operation of a Ho:YAG laser, intracavity pumped by a diode-bar-pumped Tm:YAG laser, is reported. At rod mount temperatures of 10 degrees C, for both the Tm:YAG and the Ho:YAG rods, we obtained 2.1 W of output at 2.097mum from the Ho:YAG laser for 9.2 W of diode power incident upon the Tm:YAG rod.     

Injection-seeded Tm:YAG laser at room temperature

The solid-state, tunable, narrowband, high pulse energy and high reliability lasers are attractive source for LIDAR system. In this paper, we demonstrated a diode pumped injection-seeded 2 μm Tm:YAG laser. By inserting two F-P etalons into the laser cavity, linear-polarized single-frequency seed-laser was achieved at a wavelength of 2013 nm, with a maximum output power of 60 mW. Long-term and short-term frequency stability for the seed-laser were 1.27 × 10^− 7 and 97 Hz/μs, respectively. High power Q-switched laser was operated using a bowtie cavity, the bidirectional output of which was favorable for the injection-seeded. After injecting the seed-laser to the power-laser, single-frequency, nearly transform-limited pulsed 2 μm laser was obtained. As much as 2.0 mJ output energy was achieved at an operating repetition rate of 15 Hz, with a pulse width of 356.2 ns.     

Efficient Ho:YAP laser dual-end-pumped by Tm fiber laser

We report the continuous wave and acousto-optically Q-switched operation of an in-band dual-end-pumped Ho:YAP laser at room temperature. A continuous wave output power of 11.0W at 2118 nm was obtained at an absorbed pump power of 19.8 W, corresponding to a slope efficiency of 62.1%. For the Q-switched mode, a maximum pulse energy of about 1.07 mJ and a minimum pulse width of 29 ns at a repetition rate of 10 kHz were achieved, resulting in a peak power of 36.9 kW.     

Diode-side-pumped AO Q-switched Tm,Ho:LuLF laser

A diode-side-pumped Tm,Ho:LuLiF laser at 2-m wavelength obtained in a ring resonator and its amplification experiment are reported. At the maximum pump energy of 4.7 J available for the oscillator,the output energy per pulse for the oscillator decreases from 904 to 483 mJ in free running mode,and decreases from 106 to 68 mJ in Q-switched mode,with an increase of pump pulse repetition rate from 1 to 5 Hz. When considering the amplifier,99-mJ Q-switched output energy is achieved at 5-Hz repetition rate.     

1645 nm Q-Switched resonantly pumped Er:YAG laser

A resonantly pumped Q-switched Er:YAG laser at 1645 nm was reported. 1 mJ of output pulse energy was achieved for Q-switched operation at 100 Hz repetition rate under total incident pump power of 4 W. An output peak power of 14 kW and pulse width of 60.6 ns were obtained.     

Conductively cooled 1-kHz single-frequency Nd:YAG laser for remote sensing

A conductively cooled,laser diode(LD) end-pumped,injection-seeded single-frequency Nd:YAG laser is designed and implemented.The laser is capable of producing an 8-mJ Q-switched pulse with a 11-ns pulse width at 1 064 nm and at a pulse repetition rate of 1 000 Hz.At the maximum output energy of 8 mJ,the frequency jitter is less than 3.5 MHz(root mean square(RMS)) over two minutes,and the linewidth is around 54.2 MHz.The M2 of the laser beam is approximately 1.30 in both horizontal and vertical directions.The optimized ramp-fire technique is applied to build reliable single longitudinal mode oscillating.     

Efficient diode-pumped passively Q-switched laser with Nd:YAG/Cr:YAG composite crystal

Diffusion bonded Nd:YAG/Cr:YAG composite laser crystal has been employed to perform a compact diode-pumped passively Q-switched laser. At the incident pump power of 3.3 W and pulse repetition rate of 16.3 kHz, the maximum average output of 592 mW has been obtained, corresponding to an optical-to-optical conversion efficiency of 18%. Stable passively Q-switched operation with peak power of 6.5 kW and pulse duration of 6 ns was also achieved. It has been experimentally revealed that Nd:host/Cr:YAG composite structure is a promising material for compact cost-effective Q-switched laser sources with high-peak power and short pulse duration. In addition, thermal lens effect (TLE) in the active medium and its impact on the Q-switched laser performance have been analyzed.     

Fiber-coupled diode end-pumped Q-switched Tm,Ho:YLiF4 laser

At liquid-nitrogen temperature, at 10-kHz pulse repetition rate, Q-switched 36-ns pulses with average output power of 4 W at 2.05 μm and 4.5-W continuous wave output power with a total optical-optical conversion efficiency of 30%, were achieved from a 6% Tm, 0.5% Ho:YLiF4 laser. This laser was endpumped by a fiber-coupled laser diode emitting up to 15 W around 792 nm. The 1-m-long optical fiber carrying the pump radiation has a core diameter of 700 μm with a numerical aperture of 0.22.     

Continuous-wave operation of a room-temperature Tm: YAP-pumped Ho: YAG laser

We report a continuous-wave (CW) 2.1-μm Ho:YAG laser operating at room temperature pumped by a diode-pumped 1.94-?m Tm:YAP laser.The maximum output power of 1.5 W is obtained from Ho:YAG laser,corresponding to Tm-to-Ho slope efficiency of 17.9% and diode-to-He conversion efficiency of 5.6%.     

Q-switched Ho:YAP laser with a volume bragg grating pumped by a Tm-doped silicon fiber laser

We reported the Q-switched Ho:YAlO₃ laser with a volume Bragg grating pumped by the Tm doped fiber laser. The Ho:YAP laser maximum output energy was 1.04 mJ under the repetition frequency of 5 kHz when the incident power was 12.49 W with the threshold of 2.38 W. The Ho:YAP output wavelength was centered at 2117.9 nm with bandwidth of about 0.3 nm. The pulse width is 23.9 ns.     

Diode-end-pumped CW and actively Q-switched Tm,Ho:YLF ring laser

This paper presents CW and acoustic-optical Q-switched Tm,Ho:YLF laser performance in a laser-diode end-pumping figure-eight ring resonator structure at 77 K. Under CW operation, different transmission of output couplers and different cavity length were used to achieve best characteristics of the laser. The maximum power of 1.85 W is achieved with the threshold of 2.09 W, slope efficiency of 28.14% and optical-to-optical efficiency of 20.3% on the condition of 1 m cavity length and 18% transmission. Under pump power of 4 W, laser characteristics under Q-switched operation with different pulse repeat frequency was investigated. Maximum energy of 5.86 mJ is achieved with pulse width of 171.2 ns, peak power of 34.2 kW and dynamic-static ratio about Q-switch laser of 0.62 at pulse repeat frequency 70 Hz.     

The output characteristics of double-end-pumped Ho:LuAG laser at room temperature

Continuous-wave (CW) and Q-switched operation of a room-temperature Ho:LuAG laser was resonantly double-end-pumped by a diode-pumped Tm:YLF laser at 1.91 μm. The CW Ho: LuAG laser generated 24.5 W of linearly output at 2094.4 nm with beam quality factor of M ² = 1.11 ± 0.02 for an absorbed pump power of 44.0 W, corresponding to optical-to-optical conversion efficiency of 55.7% and slope efficiency of 60.5%. Under Q-switched operation, a maximum output power of 24.1 W with a slope efficiency of 58.1% at 12 kHz was obtained. Also, the minimum pulse width of 32 ns was achieved, corresponding to the peak power was 37.7 kW.     

50-mJ,Q-switched, 2.09-microm holmium laser resonantly pumped by a diode-pumped 1.9-microm thulium laser

We report >50-mJ Q-switched energy output from a 2.09-microm Ho:YAG oscillator, resonantly pumped at 1.9-microm by a diode-pumped Tm:YLF laser. We demonstrate a Q-switched-to-normal-mode extraction efficiency of 100% at an output energy of 30 mJ and over 64% at the 50-mJ output level. Operating at 50 mJ (60 Hz) of output, a pulse width of 14 ns is achieved from the holmium oscillator, which corresponds to approximately 3.6 MW of peak power. At the 50-mJ output level, a beam-propagation factor M2 approximately 1.2 is achieved.