Beam divergence and refractive power of directly coated solid state lasers

A relation between the far field divergence angle of a laser output beam and the elements of the laser resonator matrix is derived. This relation is applied to the resonator matrix of directly coated laser rods and yields an expression for the far field angle θ_m of the output beam in terms of the pump light induced refractive power D of the rod. By means of this expression D versus the average pumping power is calculated from the experimental values of θ_m for several laser rods and is found to be in good agreement with previously published values.     

The photodissociation of UF6 using infrared lasers

The ir collisionless multiple photon absorption (cmpa) photodissociation of UF₆ is reported. Single frequency photodissociation is a accomplished with the focused output from a pulsed CF₄ laser operating at 615 cm^-1. When focusing the CF₄ laser output with a 7.5 cm f.1. lens, photodissociation is observed at laser energies as low as 5 mJ. By using a CO₂ laser (0.7 J, 1077 cm^-1) in concert with the CF₄ laser, significant enhancement (factors of 10–100) of the photodissociation yield is obtained at low CF₄ laser energies. Electronic emission is observed from the focal region, but only when both lasers are present.     

Dual-wavelength diode-pumped laser operation of N p-cut and N g-cut Tm:KLu(WO4)2 crystals

Simultaneous continuous-wave laser oscillation at two wavelengths has been observed and studied in a diode-pumped monoclinic N _p-cut Tm:KLu(WO₄)₂ for different transmission of the output coupler. The maximum output power reached 1.15 W with a slope efficiency of 20.4 % with respect to the absorbed power for polarization parallel to the N _m optical axis. In an analogous N _g-cut crystal, the dual-wavelength laser operation is accompanied by polarization switching with increasing pump power and the switching point depends on the output coupling. The thresholds are slightly higher, and the slope efficiency reached a maximum of 25.5 % for polarization parallel to N _m at low pump levels, but at high pump levels, the oscillating polarization is parallel to N _p, reaching maximum output power of 3.09 W. Simple modelling with rate equations taking into account reabsorption losses explains qualitatively the complex behavior observed in the continuous-wave laser experiments with this anisotropic biaxial laser crystal.     

Efficient High-Power Ho:YAG Laser Pumped by Dual-End-Diode-Pumped Tm:YLF Laser

We report a Ho:YAG (Ho-doped yttrium aluminum garnet) laser pumped by a dual-end-diode-pumped Tm:YLF (Tm-doped yttrium lithium fluoride) laser to obtain an efficient experimental device with high output-power characteristics. We study the influence of the specific values of the output coupling mirror transmittance, the resonant cavity length, and the radius of curvature of the output coupling mirror on the Ho:YAG laser output characteristics. Under optimum experimental conditions, under which the output coupling mirror transmittance was 30%, the resonant cavity length was 25 mm and the output coupling mirror radius of curvature was 300 mm, and the maximum pumping power of the dual-end-diode-pumped Tm:YLF laser was 15.2 W. We obtain an efficient high-power 2.122-μm laser output of 7.98 W from the Ho:YAG laser. The optical-to-optical conversion efficiency is 52.5%, and the beam quality factor figures are M _x ² ?=?2.89 and M _y ² ?=?2.97.     

Frequency measurement of the 496 μm line of a CH3F FIR laser

A direct frequency measurement of the 496 μm, K = 2 line from a CH₃F laser is reported. Our laser is a metallic wave-guide device pumped by a frequency stabilized CO₂ laser; its output is mixed in a CaAs-Au Schottky barrier diode with a 100 GHz klystron and the beat note is observed on a spectrum analyzer. The result is f_CH3F(496 μm, K = 2) = 604 297.5 ± 0.2 MHz.     

Holmium laser in-band pumped by a thulium laser in the same host of YAlO3

We report on the room-temperature continuous-wave (CW) operation of a Ho:YAlO₃ laser that is resonantly end pumped at 1.94 μm by a diode-pumped thulium-doped laser in the same host. Through the use of a 1 at % Ho³⁺-doped 20-mm-long YAlO₃ crystal (b cut), the Ho:YAlO₃ laser generated 1 W of linearly polarized (E//c) output at 2118 nm and 0.55 W of E//a output at 2128.5 nm for an incident pump power of 5 W, with an output coupler transmission of 14 and 3%, respectively. An optical-to-optical conversion efficiency of 20% and a slope efficiency of 33% were achieved at 2118 nm corresponding to an incident pump power.     

Diode-end-pumped frequency-doubled Nd:YAP/Cr:YAG laser using a KTP crystal

We present a design for a compact laser-diode-end-pumped Nd:YAP/Cr:YAG q-switched laser in a plano?Cconcave cavity configuration. With an optical-to-optical efficiency of 35%, this laser provides an average output of 1.2 W with 13 mJ at 1080 nm. After that, the laser is frequency doubled by replacing the output coupler with a flat KTP crystal to achieve an output of 8 mJ in 8 ns at 540 nm. At a peak power of 1 MW, the laser emits linearly polarized output with an average power of 800 mW. The calculated M² value is 1.3, the output is very stable, and the laser operates in the TEM₀₀ mode.     

Multi-wavelength diode-pumped Nd:LGGG picosecond laser

Laser operation near 1.06 μm by a diode-pumped Nd:(Lu _x Gd_1?x )₃Ga₅O₁₂ (Nd:LGGG) disordered crystal has been investigated. Cw oscillation, with a slope efficiency as high as 61% and 230 mW output power, was achieved with 400 mW absorbed power from a 1-W laser diode. Stable passive mode locking with single- or multi-banded spectrum was obtained with a semiconductor saturable absorber mirror (SAM) and a single-prism, dispersion-compensated cavity. Fourier limited pulses with duration ≈3–9 ps and output power ≈40 mW were generated at three well-defined laser transitions in the range 1062–1067 nm.     

Review of Ni-like ion X-ray laser research at Lawrence Livermore National Laboratory

We have demonstrated saturated output on several nickel-like ion X-ray lasers ranging from niobium to silver by using a psec, high-power, chirped-pulse-amplification, tabletop laser. These results have been achieved at wavelengths from 20.3 to 13.9 nm on the Ni-like 3d⁹4d¹S₀→3d⁹4p¹P₁ laser line using a total of 5 to 7 J of energy in a traveling wave excitation scheme. Strong amplification is also observed for Ni-like Sn at 11.9 nm. Gain of 41 cm⁻¹, gain-length product of 18, and output energy of 12 μJ are measured for the Ni-like Pd line at 14.7 nm. For Ni-like Mo, experiments are done using multilayer mirrors to obtain two-dimensional images of the output aperture of the laser and to measure the total laser energy as a function of various parameters such as the delay between the short and long pulses and the energy of the two pulses. For Mo we measure an output energy of 2 μJ and a gain-length product of 16.6. To model the Mo experiments, the LASNEX code is used to calculate the hydrodynamic evolution of the plasma and provide the temperatures and densities to the XRASER code, which then does the kinetics calculations to determine the gain. The temporal and spatial evolution of the plasma is studied both with and without radiation transport included for the 4f and 4p→3d Ni-like Mo resonance lines. High gains are predicted and observed for both the 3d⁹4d¹S₀→3d⁹4p¹P₁ laser line at 18.9 nm and the 3d⁹4f¹P₁→3d⁹4d¹P₁ photopumped line at 22.6 nm.     

Pulsed Nd:YAG passive Q-switched laser using Cr4+:YAG crystal

In this paper, we report the experimental results of a pulsed flash lamp Nd:YAG laser at wavelength of 1064 nm and Q-switched by Cr⁴⁺:YAG solid state saturable absorber. We have obtained the output energy (E) and pulse- width (τ_p) of this laser for various initial transmissions of this saturable absorber. Furthermore, the effect of reflectivity of the output coupler (R), diameter of the rod (d), and optical length of the cavity (l) on this laser output data have been investigated. We have used the corner cube as a back mirror, which shows high laser stability and better brightness. We have obtained pulse-width 15 ns with 31 mJ output energy. We have also analyzed this laser theoretically and analytically, which agrees well with our corresponding experimental results.     

1 mJ Passively Q-switched Nd:YAB laser using a V:YAG crystal

We describe the design and operation of a diode-pumped compact and efficient Nd:YAB laser operating at 1338 nm. We use a passive Q-switch V:YAG crystal to achieve 1 mJ Q-switched pulses at the laser output. The laser elaborated provides an average power of 1.5 W in the CW regime and 1 W in Qswitched mode with an optical efficiency of 15 and 10%, respectively. A 65 mm plano-concave cavity is formed with an output in the TEM₀₀ mode. At a pulse width of 15 ns, the achieved peak power is 66 kW.     

Intracavity frequency doubling of an active Q-switched Nd:YAG laser with 2.25 W output power at 473 nm

An active Q-switched diode-end-pumped Nd:YAG laser is reported with 2.9 W output power on the ⁴F_3/2 → ⁴I_9/2 transitions at a pump power of 24 W. With intracavity frequency doubling using a 20-mm-long LBO, a maximum blue output power of 2.25 W is achieved at a repetition rate of 23 kHz. The conversion efficiency from the corresponding Q-switched fundamental output to blue output is 96%. The peak power of the Q-switched blue pulse is up to 610 W with 160 ns pulse width. The fluctuation of the blue output power is less than 4.0% at the maximum output power.     

Continuous-wave Nd:YVO4/KTiOPO4 green laser at 542 nm under diode pumping into the emitting level

We report a green laser at 542 nm generation by intracavity frequency doubling of a continuous wave (CW) laser operation of a 1086 nm Nd:YVO₄ laser under 880 nm diode pumping into the emitting level ⁴ F _3/2. A KTiOPO₄ (KTP) crystal, cut for critical type I phase matching at room temperature is used for second harmonic generation of the laser. At an incident pump power of 14.5 W, as high as 1.33 W of CW output power at 542 nm is achieved. The optical-to-optical conversion efficiency is up to 9.2%, and the fluctuation of the green output power was better than 3.8% in the given 30 min.     

Diode-pumped orthogonally polarized dual-wavelength Nd3+:LaBO2MoO4 laser

Polarized spectroscopic properties related to 1.07 μm laser operation of a 1.8 at.% Nd³⁺:LaBO₂MoO₄ crystal grown by the Czochralski method were investigated at room temperature. Using a 2.2-mm-thick, Z-cut Nd³⁺:LaBO₂MoO₄ crystal as gain medium, orthogonally polarized dual-wavelength laser at 1,068 and 1,074 nm was first realized in a plano-concave resonator end-pumped by a quasi-continuous-wave 795 nm diode laser. A total output peak power of 1.2 W with slope efficiency of 26 % around 1.07 μm was obtained. The influences of resonator length and pump power on output laser wavelength were also investigated.     

Evaluation of the Performance of an HO:yap Laser Resonantly Pumped by a Thulium Fiber Laser

We investigate the continuous-wave performance of an Ho:YAP laser resonantly pumped by a Tm fiber laser at different output transmittance of 20 %, 30 %, and 50 %. We use a 40 mm long a-cut crystal with 0.5 at.% Ho ion. Our experimental results show that the best power performance is obtained at an output transmittance of 30 %. At an absorbed pump power of 12.1 W, we obtain a maximum output power of 6.1 W at 2118.1 nm with a slope efficiency of 63.4 %. The laser operates at the TEM₀₀ mode with a beam quality factor M ₂ ~ 1.5 measured using a 90/10 knife-edge method.     

High efficiency and good beam quality of electro-optic, cavity-dumped and double-end pumped Nd:YLF laser

In this paper, we describe a Nd:YLF laser based on high-speed RTP electro-optical cavity dumping technique. Two home-made 150 W fiber pump modules are used from both sides to pump Nd:YLF crystal. Coupling systems are the key elements in end-pumped solid-state lasers, the aberrations of which greatly affect the efficiency of the lasers. In order to get high efficient and good quality laser output, the optical software ZEMAX is used to design a four-piece coupling system. When the pumped energy is 32 mJ at the repetition rate of 1 Hz, the output energy is 6.5 mJ with 2.5 ns pulse width. When the pumped energy is 13.1 W at the repetition rate of 200 Hz, the output energy is 2.2 W with small M ² factor where M _x ² is 1.04, and M _y ² is 1.05, and the light-light conversion efficiency is up to 16.8%.     

An Intracavity-Triggered Passively-Switched Nd:YVO<Subscript>4</Subscript> Laser

We demonstrate an intracavity-triggered passively Q-switched Nd:YVO₄ laser within a diode-end-pumped configuration. We employ a Cr⁴⁺:YAG saturable absorber as the passive Q switch and an Nd:LiYF₄ (YLF) laser as the laser triggering of the Q-switched laser. Since we use the same Cr⁴⁺:YAG crystal and output coupler with the Nd:YVO₄ laser, the Cr⁴⁺:YAG Q switch is triggered inside the Nd:YLF laser cavity. As a result, the timing jitter in standard deviation of Nd:YVO₄ laser can be reduced to 16 ns.     

Use of induced spatial incoherence for uniform illumination of laser fusion targets

We report a technique to achieve very uniform illumination of laser irradiated targets by inducing a controlled amount of transverse spatial incoherence in the output beam of a broadband laser. The spatial incoherence is created by imposing different optical delays upon different transverse sections of the beam, and choosing the delay increments to be larger than the laser coherence time t_c=1/δν. This technique may allow easy attainment of the pellet illumination uniformity required for laser fusion.     

Diode-side-pumped Nd:GGG laser at 1,105?nm and frequency-doubled laser at 552?nm

A high-power diode-side-pumped 1,105?nm Nd:GGG laser and a laser at 552?nm based on intracavity frequency doubling of 1,105?nm laser are demonstrated for the first time. A 26.8-W 1,105?nm laser continuous wave output was achieved under the incident pump power of 170?W. A LiB₃O₅ crystal is used for second harmonic generation of 1,105?nm laser. When the pump power was 170?W, the average output power at 552?nm of 7.3?W was obtained, corresponding to the optical conversion efficiency of 4.3?%. And the minimum pulse width is 181?ns with the pulse repetition rate of 10?kHz. The M ² factors are measured to be 19.8 and 17.6 in the horizontal and vertical directions, respectively.     

Diode-pumped monolithic Er3+:Yb3+:YAl3(BO3)4 micro-laser at 1.6 μm

Efficient eye-safe 1.6 μm monolithic laser was realized in a c-cut, 0.7-mm-thick Er³⁺:Yb³⁺:YAl₃(BO₃)₄ microchip end-pumped by a quasi-continuous-wave 970 nm diode laser. At incident pump peak power of 20.4 W, a maximum output peak power of 2.6 W with a slope efficiency of 19% was obtained when the waist radius of pump laser beam was 220 μm. The spectra and profiles of output beam of the Er³⁺:Yb³⁺:YAl₃(BO₃)₄ monolithic laser were measured. The influences of the waist radius of pump laser beam on the slope efficiency and threshold of the monolithic laser were also investigated.