Stable room-temperature LiF:F2 (+*) tunable color-center laser for the 830-1060-nm spectral range pumped by second-harmonic radiation from a neodymium laser

Simultaneous photostability and thermostability of a room-temperature LiF:F2(+*) tunable color-center laser, with an operating range over 830-1060 nm, pumped by second-harmonic radiation of a YAG:Nd(3+) laser with a 532-nm wavelength has been achieved. The main lasing characteristics of the obtained LiF:F2 (+*) laser have been measured. Twenty-five percent real efficiency in a nonselective resonator cavity and 15% real efficiency in a selective resonator cavity have been obtained. The stable LiF:F2 (+*) laser operates at a 1-100-Hz pulse-repetition rate with a 15-ns pulse duration, a 1-1.5-cm(-1) narrow-band oscillation bandwidth, and divergency of better than 6 × 10(-4). Doubling the fundamental frequencies of F2(+*) oscillation made it possible to obtain stable blue-green tunable radiation over the 415-530-nm range.     

Diode-Pumped Tunable Room-Temperature LiF:F(2)(-) Color-Center Laser

Pulsed room-temperature tunable operation of a diode-pumped LiF:F(2)(-) laser has been demonstrated for the first time to the author's knowledge. The LiF:F(2)(-) oscillator was tunable in the 1122-1201-nm range. In the free-running mode, with a nonselective resonator, the LiF:F(2)(-) laser showed a 4% optical-to-optical conversion efficiency and a measured 2.5% pumping-to-lasing efficiency at the maximum of the tuning curve for tunable narrow-band operation.     

Multiline, superbroadband and sun-color oscillation of a LiF:F(2)(-) color-center laser

We report experimental and theoretical studies of the temporal, spectral, and spatial features of a superbroadband laser. The results obtained show that the superbroadband room-temperature operable LiF:F(2)(-) color-center laser can provide low-coherence, high-intensity laser radiation with a spectral width of 1400 A centered at 1.14 mum and 700 A in the visible range from green to red and exhibit good spatial collimation with a divergence of between 5 and 6 mrad. Oscillation of all the lines of a superbroadband spectrum is completely synchronous and occurs almost simultaneously with the pump pulse, exhibiting 4-9-ns pulse delay at 20-ns pump pulse duration. Second-harmonic generation of superbroadband oscillation spectrum was realized with an overall efficiency of 10%.     

Comparative study of tunable room-temperature laser operation in the 900-1100-nm range: LiF:F2+ and Ti3+:sapphire

We report on a comparative evaluation of efficient room-temperature solid-state lasers based on Ti:sapphire and LiF:F(2)(+) operating in the 900-1100-nm range. LiF:F(2)(+) lasers are shown to operate with substantially lower threshold, broader tuning, and higher output pulse energies. The shorter fluorescence lifetime in LiF:F(2)(+) leads to higher peak output powers and a considerable reduction in buildup-time fluctuations. The main limitations on LiF:F(2)(+) laser operation are identified as amplified spontaneous emission (ASE) and long-term thermal degradation of the color centers. ASE restricts the tuning range, slope efficiency, and bandwidth of the LiF:F(2)(+) laser for high pump intensity, but broader tuning is achieved with longer pump pulses. The beam quality of the LiF:F(2)(+) laser is comparable with that of the Ti:sapphire laser.     

Narrow-linewidth, tunable ultraviolet, Ti:sapphire laser for environmental sensing

We describe a compact, narrow-linewidth, etalon-tuned titanium:sapphire laser cavity that is designed for field environmental sensing and is pumped by the second harmonic of a kilohertz Nd:YAG laser. The fundamental tunable range is from 690 to 1100 nm, depending on mirror reflectivities and the optics kit used. The conversion efficiency is at least 25% for the fundamental and 2-3% for intracavity frequency doubling from 3.5 to 4 W 532 nm pump power. The linewidth is <0.1 cm(-1), and the pulse width is 18 ns. Applications of this cavity include the measurement of trace gas species by laser-induced fluorescence, cavity ringdown spectroscopy, and micropulse lidar in the UV-visible regions.     

All-solid-state tunable DCM dye laser pumped by a diode-pumped Nd:YAG laser

Lasing is observed near 620 nm in a DCM dye doped TiO(2)-content organically modified silicate (ORMOSIL) pumped by frequency-doubled radiation from a diode-pumped Q-switched Nd:YAG laser. The laser wavelength is tunable over 60 nm. A conversion efficiency of 18% is obtained at its central wavelength of 621 nm. The laser output energy has only a 10% reduction after 27,000 pulses at a pump repetition rate of 30 Hz and a pump intensity of 1 J/cm(2). An all-solid-state, compact, long-lifetime, and tunable dye laser has been demonstrated.     

Tunable coherent infrared generation near 2.5 microm from self-difference frequency mixing in YAl3(BO3)4:Nd3+

Idler generation from self-difference frequency mixing of the pump wave near 750 nm and the 1062-nm Nd3+ laser emission in the bifunctional laser and nonlinear optical YAl3(BO3)4:Nd3+ crystal was shown. The efficiency was 0.37%, and the infrared wavelength was tunable in the 2430-2600-nm range. New Sellmeier formulas that predict phase-matching polar angles for frequency conversion processes involving wavelengths up to 2600 nm were established.     

Double-end-pumped Nd:YVO4 slab laser at 1064 nm

We demonstrate a high-power laser diode stacks double-end-pumped Nd:YVO4 1064 nm slab laser with a folded stable-unstable hybrid resonator. An output power of 220 W was obtained at the pump power of 490 W with optical conversion efficiency of 44.9%. At the output power of 202 W, the M2 factors in the unstable direction and in the stable direction were 1.7 and 2.3, respectively.     

Highly efficient, widely tunable, 10-Hz parametric amplifier pumped by frequency-doubled femtosecond Ti:sapphire laser pulses

We report a 10-Hz, highly efficient, widely tunable (from the visible to the IR), broadband femtosecond optical parametric generator and optical parametric amplifier (OPA) in BBO, LBO, and CBO crystals pumped by the frequency-doubled output of a regeneratively amplified Ti:sapphire laser at 400 nm. The output of the system is continuously tunable from 440 nm to 2.5 mum with a maximum overall efficiency of ~25% at 670 nm and an optical conversion efficiency of more than 36% in the OPA stage. The effects of the seed beam energy, the type of the crystal and the crystal length, and the pumping energy of the output of the OPA, such as the optical efficiency, the bandwidth, the pulse duration, and the group velocity mismatch between the signal and the idler and between the seeder and the pump, are investigated. The results provide useful information for optimization of the design of the system.     

Watt-level Q-switched Nd:LuVO4 laser based on a graphene oxide saturable absorber

The demonstration is reported of a diode-pumped passively Q-switched Nd:LuVO₄ laser at 1064 nm using a transmission-type graphene oxide as the saturable absorber. The graphene oxide saturable absorber with a modulation depth of 10% was fabricated using a vertical evaporation method. With a pump of 11.5 W, a maximum output power of 1.353 W was obtained with 186-ns pulse duration and 336.7-kHz repetition rate, corresponding to a maximum pulse energy of 4 μJ per pulse.     

Compact efficient eye-safe intracavity optical parametric oscillator with a shared cavity configuration

We present a compact efficient eye-safe intracavity optical parametric oscillator pumped by a passively Q-switched Nd:YAG laser in a shared cavity configuration. A signal pulse of 3.3 mJ energy at a 1573 nm wavelength with a peak power of 150 kW was achieved. The effective conversion efficiency with respective to the optimized 1064 nm Q-switched pulse energy was as high as 51%.     

钛宝石泵浦Cr,Nd:YAG微片的自调Q激光特性

用连续的钛宝石激光泵浦１mm厚的Cr^4 ,Nd^3 ;YAG晶体微片获得了１．０６４μm的自调Ｑ激光输出,输出的激光调Ｑ脉冲非常稳定,泵浦的阈值功率为３０mW,脉冲宽度为１００ns随着泵浦功率的变化,脉冲宽度保持不变,而重复率则在变化。斜率效率随着输出耦合镜透过度的变化而变化,当输出耦合率为５％时,斜率效率高20%.一研究有助于进一步发展激光二极管泵浦的全固化的自调Ｑ微片激光器。     

Laser-diode-pumped passively Q-switched Nd:YVO4 green laser with periodically poled KTP and GaAs saturable absorber

A laser-diode-pumped passively Q-switched Nd:YVO₄ green laser with periodically poled KTP (PPKTP) and GaAs saturable absorber has been realized. The dependences of pulse repetition rate, pulse energy, pulse width and peak power on incident pump power for the generated-green-light pulses are measured. At the maximum incident pump power of 4.1 W, the maximum average output power of 113 mW is obtained, corresponding to an optical conversion efficiency of 2.8%. At the same pump power, stable green laser pulses of duration of 44.6 ns and energy of 0.28 µJ are generated at a repetition rate of 403.4 kHz. The coupling wave rate equations for a passively Q-switched laser are also given and the numerical solutions agree with the experimental results.     

Compact 50-Hz terawatt Ti:sapphire laser for x-ray and nonlinear optical spectroscopy

We report a high-repetition-rate, compact terawatt Ti:sapphire laser system. The oscillator produces an 82-MHz pulse train consisting of broad-bandwidth pulses of 0.5-nJ/pulse energy and of 9-fs pulse duration. The spectrally shaped, lambda/4 regenerative amplifier supports an 80-nm bandwidth. A single 50-Hz repetition-rate pump laser pumps both the regenerative amplifier and a multiple-pass amplifier. The final output from this laser is a 50-Hz pulse train made from pulses of 53 mJ/pulse energy and of 24-fs pulse duration. For generating ultrafast x-ray pulses, 90% of the energy from the final output of a 28-mm-diameter (1/e2) beam is focused onto an ultrafast x-ray wire target. The energy conversion efficiency from optical (800-nm central wavelength) to x-ray (characteristic lines of K(alpha) from Cu at 8 keV) pulses is estimated to be 7 x 10(-5). This laser system can also generate a lower-peak-power, dual-pulse output that can excite, simultaneously and coherently, Raman modes within an adjustable bandwidth (up to 700 cm(-1)) and at a tunable central vibrational frequency. Preliminary results for the generation of dual-pulse output and ultrafast x rays are presented.     

Performance of diode-end-pumped Cr, Nd:YAG self-Q-switched and Nd:YAG/Cr:YAG diffusion bonded lasers

Self-passively Q-switching of a diode-pumped Cr,Nd:YAG, where the Cr⁴⁺ is used as a saturable absorber for the 1064 nm laser emission is reported. The maximum average output power was obtained using an output coupler of R=86%. The self-Q-switched diode pumped laser yielded 1.86-W average output power with low threshold pumping power (≈1.7-W), average slope efficiency of ≈34%, pulse duration of about 14–16 ns, and modulation frequency ranging from 2.4 to 73 kHz, depending on the input pumping power. These results are the highest reported for self-Q-switched lasers. Higher slope efficiency (42%) and shorter Q-switched pulses were obtained for a Q-switched Nd:YAG/Cr⁴⁺:YAG diffusion bonded laser. A comparison of the codoped Cr,Nd:YAG laser performance, with that of a diffusion bonded laser is reported and analyzed.     

Efficient Nd:YAG laser end pumped by a high-power multistripe laser-diode bar with multiprism array coupling

A 10-W laser-diode bar, a multistripe monolithic laser-diode array, has been used to end pump Nd:YAG. Twelve beams emitted from 12 stripes, spaced 800 μm apart, of a 1-cm linear diode array were collimated with a multiprism array consisting of 14 prismlets with 800-μm width to pump the Nd:YAG facet. The maximum Nd:YAG cw output power at 1064 nm of 3 W was obtained at 10-W laser-diode-bar power with a slope efficiency of 35%, and a TEM(00) spatial mode with values of beam-quality factor M(2) of 1.29 and 1.76 in the planes perpendicular and parallel to the junction, respectively. A pulse width of 25.2 ns (1-kHz repetition) was obtained in acousto-optic Q-switched operation.     

Efficient pumping scheme for neodymium-doped materials by direct excitation of the upper lasing level

An efficient pumping scheme that involves direct excitation of the upper lasing level of the Nd(3+) ion is demonstrated experimentally. The results obtained for direct upper laser level pumping of Nd:YAG R2 (869 nm) and Nd:YVO(4) (880 nm) were compared with traditional ~808-nm pump band excitation. A tunable cw Ti:sapphire laser was used as the pump source. In Nd:YAG, the oscillator slope efficiency increased by 10% and the threshold decreased by 11%. In Nd:YVO(4), the slope efficiency increased by 5% and the threshold decreased by 11%. These results agree with theory. The increase in optical efficiency indicates that laser material thermal loading can be substantially reduced.     

Extra-cavity, widely tunable, continuous wave MgO-doped PPLN optical parametric oscillator pumped with a Nd:YVO4 laser

An extra-cavity, widely tunable, and continuous wave (CW) singly resonant optical parametric oscillator (SRO) based on MgO-doped periodically poled lithium niobate (PPMgLN) has been developed. A Nd:YVO₄ laser pumped by 808 nm laser diode array (LDA) is used as the pump source. The threshold value of the SRO system is only 1.86 W at 1064 nm. 1101.1 mW of idler output at 3.217 μm and 2004.3 mW of signal output at 1.590 μm have been achieved when the pump power is 8.76 W, and this corresponds to a total (idler + signal) optic–optic conversion efficiency of 35.5%. The periods of the domain structure on the PPMgLN wafer can be changed by shifting the PPMgLN crystal, thus enabling a widely tunable mid-infrared spectrum of 3.026–4.485 μm, and signal wavelengths widely tunable in range of 1.395–1.641 μm. Along with the signal and idler light, the visible and near-infrared spectrum (697.5–820.5 nm, 603.6–645.5 nm, 532 nm, 421.3–463.3 nm) is observed. This OPO system is compact, simple and operated at room temperature.     

High-power narrow-linewidth quasi-CW diode-pumped TEM00 1064 nm Nd:YAG ring laser

We demonstrated a high average power, narrow-linewidth, quasi-CW diode-pumped Nd:YAG 1064 nm laser with near-diffraction-limited beam quality. A symmetrical three-mirror ring cavity with unidirectional operation elements and an etalon was employed to realize the narrow-linewidth laser output. Two highly efficient laser modules and a 90° quartz rotator for birefringence compensation were used for the high output power. The maximum average output power of 62.5 W with the beam quality factor M(2) of 1.15 was achieved under a pump power of 216 W at a repetition rate of 500 Hz, corresponding to the optical-to-optical conversion efficiency of 28.9%. The linewidth of the laser at the maximum output power was measured to be less than 0.2 GHz.     

Diode-laser-array end-pumped 1W CW Nd:YVO4/BIBO green laser

Abstract

This paper discusses a diode-laser-array end-pumped Nd:YVO₄/BIBO green laser. Using a three-mirror folded cavity (V-shaped), a 1.06 W CW green output was obtained at an incident pump power of 8.5 W; the corresponding optical conversion efficiency was 12.5%. The relationship between the green output and the temperature of the BIBO crystal was investigated. The laser damage threshold of BIBO crystal was measured to be 600 MW cm^?2 and 400 MW cm^?2 at 1064 nm and 532 nm, respectively.