Analysis of New Q-switched Erbium Doped Fiber Laser Based on Fiber Grating Loop Mirror

An all fiber wavelength selective Q switching modulator based on fiber grating loop mirror is proposed. A newly configured Q switched erbium doped fiber laser using this all fiber modulator is numerically analyzed taking into account the effects of the spontaneous emission.

Watt-level acousto-optically Q-switched Pr:YLF laser at 639 nm

We present a study on a watt-level acousto-optically Q-switched Pr:YLF laser at three different repetition rates(10 kHz,20 kHz,and 50 kHz)for the first time,to the best of our knowledge.The corresponding average output powers and pulse widths were measured to be 1.14 W,1.2 W,and 1.32 W,and 40 ns,52 ns,and 80 ns,respectively.A maximum pulse energy of0.11 mJ was obtained,corresponding to a peak power of up to 2.8 kW at a repetition rate of 10 kHz.The simulated dynamics of a fast Q-switched Pr:YLF laser is in agreement with the experiment.The laser's ability to generate stable pulses with high peak power and short pulse width makes it highly desirable for various practical applications,such as laser machining and material processing.

Passive Q-switching of diode-pumped Yb:YAG microchip laser with ion-implanted GaAs

We reported a passive Q-switched diode laser pumped Yb: YAG microchip laser with an ion-implanted semi-insulating GaAs wafer. The wafer was implanted with 400-keV As+ in the concentration of 1016 ions/cm2. To decrease the non-saturable loss, we annealed the ion-implanted GaAs at 500℃ for 5 minutes and coated both sides of the ion-implanted GaAs with antireflection (AR) and high reflection (HR) films, respectively. Using GaAs wafer as an absorber and an output coupler, we obtained 52-ns pulse duration of single pulse.

Subharmonic mode locking of a Q-switched Nd:YAG laser

A Q-switched Nd:YAG laser has been actively mode-locked at a subharmonic frequency for the first time,to the authors’knowledge.The laser operation mode is provided by a combination of a traveling wave acousto-optic modulator and a spherical cavity mirror.The dynamics of laser generation is investigated.Pulses with a duration of 70 ps and a peak power of about 10 MW were obtained.Also presented are new results on obtaining high-power[~60 kW]picosecond tunable radiation in the~620 nm region based on frequency conversion of a superluminescent parametric generator pumped by such a laser.

Study of passive Q-switching for flash-lamp-pumped 1.34-μm Nd:GdVO_4 laser

The static laser performance of a-growth Nd：GdVO4 crystal （a-cut, 4 × 4 × 25 （mm）） at 1.34 μm pumped by flash-lamp is investigated with different transmissions of output couplers. With the output coupler transmission of T = 30%, the static output energy of 148 mJ is obtained when the pump energy is 35.2 J, and the corresponding electric-optical conversion efficiency is 0.42%. The Q-switched output of lasers with the output wavelength ranging from 1.3 to 1.6 μm can be realized by using Co^2＋ ：LaMgA11O19 （Co：LMA） as saturable absorber. A flash-lamp-pumped, passively Q-switched Nd：GdVO4 laser with Co：LMA as saturable absorber is demonstrated in piano-concave laser cavity. With the cavity length of 16.3 cm and pump energy of 19.8 J, the single-pulse output energy, pulse width, and peak power are obtained to be 4 m J, 80 ns, and 5 × 10^4 W, respectively.

Experimental investigation on Q-switching and Q-switched mode-locking operation in gold nanorods-based erbium-doped fiber laser

We report on the generation of Q-switched and Q-switched mode-locked （QML） pulses in an erbium-doped fiber ring laser by using a polyvinyl alcohol （PVA） -based gold nanorod （GNR） saturable absorber （SA）. The PVA- based GNR SA has a modulation depth of -4.8% and a non-saturable loss of -26.9% at 1.5 μm. A Q-switched pulse train with a repetition rate varying from 18.70 to 39.85 kHz and a QML pulse train with an envelope repetition rate tuning from 20.31 to 31.50 kHz are obtained. Moreover, the lasing wavelengths of the Q-switched pulses can be flexibly tuned by introducing a narrow bandwidth, tunable filter into the laser cavity. The results demonstrate that the GNRs exhibit good optical performance and can find a wide range of applications in the field of laser technology.

Continuous-wave and Q-switched performance of an Yb:YAG/YAG composite thin disk ceramic laser pumped with 970-nm laser diode

Using front face-pumped compact active mirror laser （CAMIL） structure, we have demonstrated an Yb：YAG/YAG composite ceramic disk laser with pumping wavelength at 970 nm. The laser has been operated in both continuous-wave （CW） and Q-switching modes. Under CW operation, laser output power of 1.05 W with 2% transmission output coupler was achieved at the wavelength of 1031 nm. Q- switched laser output was gotten by using an acousto-optic Q-switch. The repetition rate ranged from 1 to 30 kHz and the pulse width varied from 166 to 700 ns.

Compact and high-energy diode-side-pumped Q-switched Nd:YAG slab laser system for space application

We develop a compact and high-energy Nd：YAG slab laser system consisting of an oscillator and an amplifier for space applications. The oscillator is a diode-side-pumped electro-optically Q-switched slab laser with a cross-Porro resonator. The KD＊P Pockels cell with a low driving voltage of 950 V is used to polarization output coupling. The amplifier is a Nd：YAG zigzag slab pumped at bounces. The maximum output pulse energy of 341 m3 with 13 ns pulse duration is obtained from the system at the repetition rate of 20 Hz and the beam quality factors are M2=3.1 and M2=3.5. The beam pointing stabilities of the laser system are 3.05μrad in the X-direction and 3.99 grad in the Y-direction, respectively.

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

A diode-side-pumped Tm,Ho：LuLiF laser at 2μm 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.

Diode-pumped, narrow-linewidth, linearly polarized,passively Q-switched 1645 nm Er:YAG laser

We demonstrate a narrow-linewidth linearly polarized 1645 nm Er：YAG laser, directly diode-pumped by a fiber- coupled continuous-wave laser diode at 1532 nm. Passive Q-switching is realized by a few-layer graphene satu- rable absorber. A maximum polarized average output power of 3.13 W is achieved at 23.28 W incident pump power. A pulse energy of as much as 58.8 μJ and pulse width of 4.21 μs are yielded at a 53.2 kHz pulse repetition rate. The spectrum and linewidth of the output beams are measured to be 1645.34 and 0.05 nm, respectively. This laser can be useful in the detection of atmosphere pollutants.

Passively Q-switched laser with single longitudinal mode based on the frequency selection of grating and F-P etalon in twisted-mode folded cavity

A passively Q-switched side-pumped laser with folded resonator is specially constructed for single- longitudinal-mode smooth pulse output. Nd：YAG is chosen as the laser active medium and Cr^4＋：YAG as the saturable absorber medium. Additionally, the method of frequency selection by grating with 1200 line/mm and Fabry-Perot （F-P） etalon is used in the twisted-mode cavity. The single-frequency smooth pulses are produced with 10-Hz repetition rate, 20-ns pulse width, and 1.064-μm wavelength. The proba- bility of single-frequency laser output measured is over 99% by using the methods of Fourier analysis and F-P etalon multiple-beam interferometry at the threshold voltage. The measured near-field and far-field angles of divergence are 1.442 and 1.315 mrad, respectively. The values of M^2 are 1.32 and 1.31 separately with the knife-edge method. Single pulse at 1.064 tim with the energy of 8.8 mJ is achieved in TEM00 mode.

Diode-pumped self-Q-switched Cr,Nd:YAG laser with 7-W average output power

We report a diode-pumped self-Q-switched 1064-nm Cr,Nd：YAG of 16-18 ns. The maximum average output power up to 7 W, 3370, is obtained in a simple and compact linear cavity by using transmittance of 1570. The laser operates at TEM00 mode with a laser with pulse duration in the range corresponding to a slope efficiency of a plane-concave output coupler with a pump power of 14.2 W.

Stable single-mode operation of injection-seeded Q-switched Nd:YAG laser by sine voltage modulation

Based on the modified ramp and fire technique, a novel injection seeding approach with real-time resonance tracking is successfully demonstrated in a single-frequency Nd：YAG pulsed laser. Appling a high-frequency sinusoidal modulation voltage to one piezo actuator and an adjustable DC voltage to another piezo actuator for active feedbackm single-mode laser output with high-frequency stability is obtained, and the effect of the piezo hysteresis on the frequency stability can be eliminated for a laser diode pumped @switched Nd：YAG laser at a repetition rate of 400 Hz.

Watt-level high-power passively Q-switched laser based on a black phosphorus solution saturable absorber

A novel black phosphorus （BP） solution saturable absorber （SA） is fabricated by the liquid-phase-exfoliated method and successfully used for passively Q-switched （QS） Nd：YVO4 laser. Compared with a traditional solid SA, a BP solution SA possesses more excellent optical transparency and higher damage resistance. The shortest pulse duration and highest average output power are measured to be 119 ns and 1.23 W, respectively. To the best of our knowledge, both of them are the best results among QS solid-state lasers with BP-based absorbers so far. The repetition rate is in the range of 533.2 to 722 kHz. The results indicate the potential application of the BP solution SA into high-Dower solid-state pulse lasers.

Electro-optically Q-switched 946 nm laser of a composite Nd:YAG crystal

A depolarization phenomenon in an electro-optical crystal in a quasi-three-level 946 nm Nd：YAG laser is observed. A compensation of the thermal effects in electro-optical crystals is achieved by employing a quarter-wave plate, with one optical axis parallel to the laser polarization. This technique allows for the production of an electro-optically Q-switched 946 nm Nd：YAG laser at 1 k Hz. A maximum output power of 350 m W at 1 k Hz repetition frequency and 11 ns pulse duration are achieved with an output coupler of 10% transmission under the incident pump power of 11.1 W, corresponding to a peak power of ～32 k W.

KLu(WO_4)_2 crystal as the Raman medium in a diode-pumped passively Q-switched Nd:YAG laser

A diode-pumped passively Q-switched Nd:YAG/KLu(WO 4 ) 2 (KLW) Raman laser is presented for the first time. As high as 1.89 W average output power is obtained at the pump power of 15.7 W with the pulse repetition frequency (PRF) of 27.2 kHz, and the corresponding diode-to-Stokes conversion efficiency is 12.0%. The highest pulse energy of 84.0 μJ is obtained. The obtained average output power and pulse energy are much higher than the previously reported results of diode-pumped passively Q-switched Raman lasers.

Efficient and compact diode-end-pumped conductively cooled Q-switched Nd:YLF laser operating at 527 nm

A novel, compact diode-end-pumped conductively cooled Q-switched Nd：YLF laser is developed. A diode-end-pumped pair of Nd：YLF slabs and an intracavity-frequency-doubled configuration are adopted to increase conversion efficiency. Using 49.8-mJ incident pump pulse energy at 500-Hz repetition rate, the laser obtains 11-mJ pulse energy and 5.5-W average output power at 527-nm wavelength, achieving an optical-optical conversion efficiency of 22%. The pulsewidth is less than 15 ns, and the beam quality factors are Mx2=1.28 and M y^2=1.12.

Radially polarized and passively Q-switched Nd:YAG laser with composite structure of gain medium

We report on a radially polarized and passively Q-switched Nd：YAG/Cr^4＋：YAG laser. The bulk Nd：YAG crystal is bonded with two undoped YAG crystal end caps to weaken the thermal lens effect and thus, enhance the extraction of stored energy in the bulk gain material. In the absence of active water cooling, the average laser power reaches 383 mW with 33% slope efficiency, and the laser pulse achieves 1.457-W peak power, 18.9-ns duration, and 13.9-kHz repetition rate with 97.6% polarization purity.

Semiconductor saturable-absorber mirror passively Q-switched Yb:YAG microchip laser

A compact passively Q-switched Yb：YAG microchip laser is demonstrated. Featuring a semiconductor saturable-absorber mirror （SESAM）, the laser yields pulses of 219 ps when the length of the microchip Yb：YAG crystal is 100 #m and the beam quality is M2 〈 1.3. To the best of our knowledge, pulses from the proposed laser are the shortest Q-switching pulses obtained from Yb：YAG microchip lasers currently available.

Continuous wave and passively Q-switched Nd:Lu_(0.15)^- Y_(0.85)VO_4 laser with 885nm direct pumping

The 885 nm direct pumping directly into the^4F_(3/2)emitting level of Nd^(3+)is applied on an Nd:Lu_(0.15)Y_(0.85)VO_4 crystal.The maximum output power of 2.8 W for continuous wave(CW)operation is obtained.For Q-switched operation,the maximum average output power is 1.2 W with pulse repetition of 23.69 kHz and pulse width of 35 ns at the pump power of 27.9 W.The high-quality fundamental transverse mode can be observed owing to the reduction of thermal effect for Nd:Lu_(0.15)Y_(0.85)VO_4 crystal by 885 nm direct pumping.