Operating characteristics of CW CO/sub 2/-N/sub 2/O laser

The authors have obtained the emission characteristics of a CW CO/sub 2/-N/sub 2/O laser. The CO/sub 2/ laser lines and N/sub 2/O laser lines vary according to the applied condition. Thus the operating conditions are interpreted.<>     

Modeling of continuous-wave self-frequency-doubling microchip laser for Yb/sup 3+/:YAl/sub 3/(BO/sub 3/)/sub 4/ crystal

Based on a quasi-three-level system, a model of continuous wave (CW) self-frequency-doubling (SFD) laser for the end-pumped Yb/sup 3+/:YAl/sub 3/(BO/sub 3/)/sub 4/ (Yb/sup 3+/:YAB) microchip is proposed. The effect of fluorescence concentration quenching (FCQ), the temperature distribution in the microchip medium, and then the refractive index distribution resulting from the thermal effect in the medium, the absorption of host, and the spatial distribution of SFD beam have been taken into account in the model. The calculated results are compared with those of experiments, and it reveals that this model is reasonable. It can be applied not only to the CW SFD laser of the Yb/sup 3+/:YAB microchip, but also to the quasi-three-level CW SFD laser of other microchips.     

Laser operation of epitaxially grown Yb:KLu(WO/sub 4/)/sub 2/--KLu(WO/sub 4/)/sub 2/ composites with monoclinic Crystalline structure

Epitaxial monoclinic double tungstate composites based on the strongly anisotropic KLu(WO/sub 4/)/sub 2/ (KLuW) were grown with high crystalline quality and laser operation of ytterbium was demonstrated for the first time. Highly efficient CW laser emission of an Yb:KLuW-KLuW crystal was achieved near 1030 nm. The 100-/spl mu/m-thick Yb:KLuW layer was pumped at wavelengths near 980 nm by a tapered diode laser as well as by a Ti:sapphire laser. More than 500 mW of CW output power and slope efficiencies up to 66% were obtained at room temperature without cooling.     

Efficient high-speed direct modulation in p-doped In/sub 0.35/Ga/sub 0.65/As/GaAs multiquantum well lasers

The authors demonstrate p-type modulation-doped strained-layer In/sub 0.35/Ga/sub 0.65/As/GaAs multiquantum well lasers which achieve a 3 dB direct modulation bandwidth of 20 GHz at a low CW drive current of 50 mA in a simple 3*200 mu m/sup 2/ mesa structure. For the same device dimensions, a modulation bandwidth of 30 GHz was measured at a CW drive current of 114 mA. This is the highest direct modulation bandwidth reported for any semiconductor laser.<>     

Continuous-wave erbium-diffused LiNbO/sub 3/ waveguide laser

The first integrated optical laser in LiNbO/sub 3/, doped by an indiffusion of Er/sup 3+/ prior to channel-guide fabrication by Ti diffusion is reported. Pumped by a colour centre ( lambda /sub p/=1.477 mu m), CW operation at lambda =1.532 mu m ( Delta lambda approximately 0.3 nm) with a threshold of approximately 8 mW absorbed power was achieved.<>     

THz-dual-frequency Yb/sup 3+/:KGd(WO/sub 4/)/sub 2/ laser for continuous wave THz generation through photomixing

A diode-pumped KGd(WO/sub 4/)/sub 2/ Yb/sup 3+/ doped laser has been developed for CW-THz generation. The frequency difference between the two modes is step tunable from DC to 3.1 THz. A maximum total optical output power of 120 mW CW has been obtained with a beat note linewidth narrower than 30 kHz.     

Laser-diode pumped CW Nd:GdVO/sub 4/ green laser with periodically poled KTP

A laser-diode pumped CW Nd:GdVO/sub 4/ green laser with periodically poled KTP is first reported. The TEM/sub 00/-mode green laser output power is 1.54 W at 4.44 W incident pump power, corresponding to an optical conversion of 31.5%, which is more than twice of that of the conventional KTP. The predicted results are compared with measured data and good agreement is reported.     

Laser-diode-array end-pumped 8.2-W CW Nd : GdVO/sub 4/ laser at 1.34 /spl mu/m

A laser-diode-array end-pumped 0.3-at.% Nd-doped GdVO/sub 4/ high-power continuous-wave (CW) laser operating at 1.34 /spl mu/m has been demonstrated. The maximum CW output power of 8.23 W was obtained at the incident pump power of 27.9 W, giving the corresponding optical conversion efficiency of 29.5% and the average slope efficiency of 30.2%. Two Nd : GdVO/sub 4/ crystals with Nd/sup 3+/ concentration of 0.5 and 1.14 at.% were also investigated for the comparison to show the advantage of lowly Nd-doped crystals applied to high-power lasers.     

High-power (>0.5-W CW) diode-pumped vertical-external-cavity surface-emitting semiconductor lasers with circular TEM/sub 00/ beams

We report demonstration of a new high-power semiconductor laser technology, the optically pumped semiconductor (OPS) vertical-external-cavity surface-emitting laser (VECSEL). Using diode laser pump, an OPS-VECSEL laser with a strain-compensated InGaAs-GaAsP-GaAs multiquantum-well (MQW) structure operated continuous-wave (CW) near /spl lambda//spl sim/1004 nm with record output power of 0.69 W in a TEM/sub 11/ mode, 0.52 W in a TEM/sub 00/ mode, and 0.37 W coupled to a single-mode fiber. It is feasible to produce greater than 1 W of power in a diffraction-limited circular beam from an efficient, compact, manufacturable and reliable OPS-VECSEL laser.     

alpha factor improvements in high-speed p doped In/sub 0.35/Ga /sub 0.65/As/GaAs MQW lasers

The authors investigate experimentally for the first time the improvements in the linewidth enhancement factor, alpha , resulting from simultaneous addition of strain and p-doping in high-speed GaAs-based multiquantum well lasers. The alpha factor is determined from measured changes in both gain and refractive index as a function of CW bias current, yielding alpha 3.1 and 1.4 at the threshold lasing wavelength for unstrained GaAs/Al/sub 0.25/Ga/sub 0.75/As and p-doped strained In/sub 0.35/Ga/sub 0.65/As/GaAs devices, respectively.<>     

Passive mode locking in a diode-pumped Nd:GdVO/sub 4/ laser with a semiconductor saturable absorber mirror

We demonstrate Q-switched and CW passive mode locking in a laser-diode-pumped Nd:GdVO/sub 4/ laser with a semiconductor saturable absorber mirror. The repetition rate of the Q-switched envelope increased from 23.1 to 260 kHz as the pump power increased from 1.75 to 13.0 W. At a pump power of 13.7 W, the Q-switched mode locking changed to CW mode locking. The maximum average output power of 4.9 W with a 140-MHz repetition rate was obtained at a pump power of 17.9 W and the single mode-locked pulse energy was 0.035 /spl mu/J. The CW mode-locked pulse duration was measured to be /spl sim/11.5 ps.     

Preparation and growth of thin film Pb/sub 2/Sr/sub 2/Ca/sub 0.5/Y/sub 0.5/Cu/sub 3/O/sub 8+ delta / superconductors by laser ablation

For the first time, the preparation of thin films of superconducting Pb/sub 2/Sr/sub 2/Y/sub 0.5/Ca/sub 0.5/Cu/sub 3/O/sub 8+ delta / material using standard bulk target preparation conditions and the laser ablation technique is reported. In common with much of the bulk characteristics, it is found that the width of the superconducting transition is large, extending from T/sub c,onset/ between 70-83 K and T/sub c,zero/ between 16-20 K.<>     

Passive Q-switching of an intracavity frequency doubled diode-pumped Nd:YVO/sub 4//KTP green laser with Cr/sup 4+/:YAG

A compact diode-pumped green-pulse laser has been demonstrated by using Cr/sup 4+/:YAG as a saturable absorber in a simple cavity formed by a coated Nd:YVO/sub 4/ crystal and a coated KTP crystal. When continuous-wave (CW) pumped with a fiber-coupled laser diode, the laser produces green pulses of 20-35-ns duration at 532 nm, with a repetition rate of 15-70 kHz. The highest green peak power was 80.8 W, obtained at 1.2 W of pump power, which is 320 times enhancement in comparison to a green output power of 250 mW under CW.     

Characteristics of HfO/sub 2/ pMOSFET prepared by B/sub 2/H/sub 6/ plasma doping and KrF excimer laser annealing

The electrical characteristics of HfO/sub 2/ pMOSFETs prepared by B/sub 2/H/sub 6/ plasma doping and excimer laser annealing were investigated. Various metal gate electrodes were evaluated to protect the high-/spl kappa/ oxide during laser irradiation. Although the aluminum gate electrode showed superior reflectivity to the laser, the equivalent oxide thickness was increased due to the interaction between aluminum and HfO/sub 2/, which resulted in reduced capacitance. In contrast, the Al-TaN stacked gate showed good reflectivity up to laser energy of 500 mJ/cm/sup 2/ and improved capacitance was obtained compared with the Al gate. For the first time, the electrical characteristics of a HfO/sub 2/ pMOSFET with an Al-TaN gate fabricated by plasma doping and excimer laser annealing were demonstrated. It was also demonstrated that plasma doping and excimer laser annealing combined with a metal gate could be applied for high-/spl kappa/ oxide MOSFET fabrication.     

Tunable Q-switched/cavity-dumped Z-fold CO/sub 2/ waveguide laser with two channels and common electrodes

A tunable Q-switched/cavity-dumped z-fold CO/sub 2/ waveguide laser with two channels and common electrodes is studied. The Q-switched and cavity-dumped pulse lasers have been obtained from the z-fold channel with the tunable pulse repetition frequency (PRF) of 1-70 kHz. At the Q-switched operation, the peak power is 730 W and the pulsewidth is 150 ns at the PRF of 10 KHz. At the cavity-dumped operation, the pulse laser width can be adjusted. The peak power is 6000 W with the pulsewidth of 20 ns and 3400 W for 32 ns. CW laser output has been obtained from the other channel and its frequency can be tuned by a piezoelectric transducer. The Q-switched and cavity-dumped pulse laser heterodyne waveforms are observed.     

Low-threshold high-T/sub 0/ 1.3-/spl mu/m InAs quantum-dot lasers due to p-type modulation doping of the active region

P-type doping is used to demonstrate high-To, low-threshold 1-3 /spl mu/m InAs quantum-dot lasers. A 5-/spl mu/m-wide oxide confined stripe laser with a 700-/spl mu/m-long cavity exhibits a pulsed T/sub 0/ = 213 K (196 K CW) from 0/spl deg/C to 80/spl deg/C. At room temperature, the devices have a CW threshold current of /spl sim/4.4 mA with an output power over 15 mW. The threshold at 100/spl deg/C is 8.4 mA with an output power over 8 mW.     

CHD/sub 2/OH optically pumped by a waveguide CO/sub 2/ laser: new far-infrared laser lines from the CD/sub 2/ wagging vibrational mode

For the first time, a wide tunability waveguide CO/sub 2/ laser was used to pump the CHD/sub 2/OH molecule for the generation of new FIR laser lines with a large offset. Optoacoustic signals associated with the infrared absorbing transitions of the CD/sub 2/ wagging vibrational mode served as a guide for finding new laser lines. All lines were characterized in wavelength, relative polarization, intensity, optimum pressure of operation, and precise offset measurements.     

Optical pumping of CHD/sub 2/OH and CH/sub 2/DOH methanol isotopomers by means of a new pulsed CO/sub 2/ laser: characterization of new far-infrared laser emissions

We have reinvestigated CHD/sub 2/OH and CH/sub 2/DOH methanol isotopomers as sources of far-infrared laser radiation using the optical pumping technique. A new waveguide pulsed CO/sub 2/ laser was used, that delivers high peak powers also in the 10-HP CO/sub 2/ band and has allowed us to observe 19 new far-infrared emissions from CHD/sub 2/OH and 8 new far-infrared emissions from CH/sub 2/DOH. Each of them is characterized in wavelength, pump offset from the center of the exciting CO/sub 2/ line, relative polarization, optimum operating pressure and intensity.     

Ga/sub 0.8/In/sub 0.2/As/GaAs/Ga/sub 0.51/In/sub 0.49/P buried ridge structure single quantum well laser emitting at 0.98 mu m

The first fabrication is reported of a buried ridge structure Ga/sub 0.8/In/sub 0.2/As/GaAs/Ga/sub 0.51/In/sub 0.49/P laser emitting at 0.98 mu m grown by two-step low pressure metal organic chemical vapour deposition. The width of the ridge is 2 mu m. Laser output power greater than 40 mW with a threshold current of 30 mA has been measured. A typical quantum efficiency of eta =60% was obtained without any facet coating. Excellent homogeneity and uniformity have been achieved over a wafer area of 10 cm/sup 2/.<>     

Spectroscopic analysis and diode-pumped laser results of Nd:BaY/sub 2/F/sub 8/

Single crystals of monoclinic BaY/sub 2/F/sub 8/, doped with different Nd/sup 3+/ concentrations, were successfully grown by means of the Czochralski method. Here, we present a polarized infrared (IR) spectroscopic investigation and diode-pumped continuous-wave laser results in the 1 /spl mu/m wavelength region. Moreover for the first time 1.3 /spl mu/m laser emission has been characterized. Q-switching results in the 1-/spl mu/m region are also presented.