Continuous-wave operation of GaN based multi-quantum-well laser diode at room temperature

Room-temperature operation of cw GaN based multi-quantum-well laser diodes (LDs) is demonstrated. The LD structure is grown on a sapphire (0001) substrate by metalorganic chemical vapour deposition. A 2.5 mu m x 800 mu m ridge waveguide structure is fabricated. The electrical and optical characteristics of the laser diode under direct current injection at room temperature are investigated. The threshold current and voltage of the LD under cw operation are 110mA and 10.5V, respectively. Thermal induced series resistance decrease and emission wavelength red-shift are observed as the injection current is increased. The full width at half maximum for the parallel and perpendicular far field pattern (FFP) are 12 degrees and 32 degrees, respectively.

High-Temperature Continuous-Wave Single-Mode Operation of 1.3 mu m p-Doped InAs-GaAs Quantum-Dot VCSELs

In this letter, we have demonstrated continuous-wave single-mode operation of 1.3-mu m InAs-GaAs quantum-dot (QD) vertical-cavity surface-emitting lasers (VCSELs) with p-type modulation-doped QD active region from 20 degrees C to 60 degrees C. The highest output power of 0.435mW and lowest threshold current of 1.2 mA under single-mode operation are achieved. The temperature-dependent output characteristics of QD-VCSELs are investigated. Single-mode operation with a sidemode suppression ratio of 34 dB is observed at room temperature. The critical size of oxide aperture for single-mode operation is discussed.

532 nm continuous wave mode-locked Nd:GdVO4 laser with SESAM

We obtained continuous wave mode-locked Nd-GdVO4-KTP laser with a SESAM. This is the first report of CW mode-locked Nd GdVO4-KTP laser with a SESAM to our knowledge. 396mw CW mode-locked pulse is achieved at the incident power of 7.653 W, with the repetition about 95 MHz. The pulse duration is assumed to be 5.5 ps, this is the shortest green pulse of 532 nm with SESAM. (c) 2009 by Astro Ltd. Published exclusively by WLLEY-VCH Verlag GmbH & Co. KGaA

Solid source MBE growth of quantum cascade lasers

High material quality is the basis of quantum cascade lasers (QCLs). Here we report the solid source molecular beam epitaxy (MBE) growth details of realizing high quality of InGaAs/InAlAs QCL structures. Accurate control of material compositions, layer thickness, doping profile, and interface smoothness can be realized by optimizing the growth conditions. Double crystal x-ray diffraction discloses that our grown QCL structures possess excellent periodicity and sharp interfaces. High quality laser wafers are grown in a single epitaxial run. Room temperature continuous-wave (cw) operation of QCLs is demonstrated.

Self-assembled quantum dots, wires and quantum-dot lasers

Molecular beam epitaxy-grown self-assembled In(Ga)As/GaAs and InAs/InAlAs/InP quantum dots (QDs) and quantum wires (QWRs) have been studied. By adjusting growth conditions, surprising alignment. preferential elongation, and pronounced sequential coalescence of dots and wires under specific condition are realized. The lateral ordering of QDs and the vertical anti-correlation of QWRs are theoretically discussed. Room-temperature (RT) continuous-wave (CW) lasing at the wavelength of 960 nm with output power of 3.6 W from both uncoated facets is achieved fi-om vertical coupled InAs/GaAs QDs ensemble. The RT threshold current density is 218 A/cm(2). A RT CW output power of 0.6 W/facet ensures at least 3570 h lasing (only drops 0.83 dB). (C) 2001 Elsevier Science B.V, All rights reserved.

Low-threshold diode-pumped CW passively mode-locked Nd:YVO4 lase

A low-threshold passively continuous-wave (CW) mode-locked Nd:YVO4 solid-state laser was demonstrated by use of a semiconductor saturable absorber mirror (SESAM). The threshold for continuous-wave mode-locked is relatively low, about 2.15 W. The maximum average output power was 2.12 W and the optical to optical conversion efficiency was about 32%. The pulse width was about 15 ps with the repetition rate of 105 MHz. (C) 2008 Elsevier GmbH. All rights reserved.

Room-Temperature Continuous-Wave Operation of InGaN-Based Blue-Violet Laser Diodes with a Lifetime of 15.6 Hours

We report our recent progress of investigations on InGaN-based blue-violet laser diodes (LDs). The room-temperature (RT) cw operation lifetime of LDs has extended to longer than 15.6 h. The LD structure was grown on a c-plane free-standing (FS) GaN substrate by metal organic chemical vapor deposition (MOCVD). The typical threshold current and voltage of LD under RT cw operation are 78 mA and 6.8 V, respectively. The experimental analysis of degradation of LD performances suggests that after aging treatment, the increase of series resistance and threshold current can be mainly attributed to the deterioration of p-type ohmic contact and the decrease of internal quantum efficiency of multiple quantum well (MQW), respectively.

HIGH-EFFICIENCY TOP SURFACE-EMITTING LASERS FABRICATED BY 4 IMPLANTATION USING TUNGSTEN WIRE AS MASK

We report the results of a high efficiency room temperature continuous wave (cw) vertical-cavity surface-emitting laser. The structure is obtained by four deep H+ implantation using tungsten wires as the mask. The fabrication process is the simplest ever reported in vertical-cavity surface-emitting laser fabrication. The largest differential quantum efficiency of 65% and maximum cw light output power over 4 mW have been achieved for the 15X15 mu m(2) device. (C) 1995 American Institute of Physics.

Comparative study of the mode-locking of Nd:GdVO4 and Nd:YAG lasers with semiconductor saturable absorber mirrors

Stable continuous-wave passive mode-locking of diode-end-pumped Nd:GdVO4 and Nd:YAG lasers withsemiconductor saturable absorber mirrors (SESAMs) are reported. The comparative study shows that theNd:GdVO4 crystal is efficient to decrease the Q-switched mode-locking tendency, and easier to continuous-wave (CW) mode lock than Nd:YAG.

Fiber Optic Coupling of CW Linear Laser Diode Array

Based on a set of microoptics the output radiation from a continuous wave (CW) linear laser diode array is coupled into a multi-mode optical fiber of 400 ptm diameter. The CW linear laser diode array is a 1 cm laser diode bar with 19 stripes with 100 fxm aperture spaced on 500 (xm centers. The coupling system contains packaged laser diode bar, fast axis collimator, slow axis collimation array, beam transformation system and focusing system. The high brightness, high power density and single fiber output of a laser diode bar is achieved. The coupling efficiency is 65% and the power density is up to 1.03 * 10~4 W/cm~2.

Room-temperature continuous-wave lasing from InAs GaAs quantum dot laser grown by molecular beam epitaxy

Quantum dot lasers are predicted to have proved lasing characteristics compared to quantum well and quantum wire lasers. We report on quantum dot lasers with active media of vertically stacked InAs quantum dots layers grown by molecular beam epitaxy. The laser diodes were fabricated and the threshold current density of 220 A/cm(2) was achieved at room temperature with lasing wavelength of 951 nm. The characteristic temperature To was measured to be 333K and 157K for the temperature range of 40-180K and 180-300K, respectively.

Self-assembled quantum dots, wires and quantum-dot lasers

Molecular beam epitaxy-grown self-assembled In(Ga)As/GaAs and InAs/InAlAs/InP quantum dots (QDs) and quantum wires (QWRs) have been studied. By adjusting growth conditions, surprising alignment. preferential elongation, and pronounced sequential coalescence of dots and wires under specific condition are realized. The lateral ordering of QDs and the vertical anti-correlation of QWRs are theoretically discussed. Room-temperature (RT) continuous-wave (CW) lasing at the wavelength of 960 nm with output power of 3.6 W from both uncoated facets is achieved fi-om vertical coupled InAs/GaAs QDs ensemble. The RT threshold current density is 218 A/cm(2). A RT CW output power of 0.6 W/facet ensures at least 3570 h lasing (only drops 0.83 dB). (C) 2001 Elsevier Science B.V, All rights reserved.

Characteristics of deep penetration laser welding of dissimilar metal Ni-based cast superalloy K418 and alloy steel 42CrMo

Experimental trials of autogenous deep penetration welding between dissimilar cast Ni-based superalloy K418 and alloy steel 42CrMo flat plates with 5.0 mm thickness were conducted using a 3 kW continuous wave (CW) Nd:YAG laser. The influences of laser output power, welding velocity and defocusing distance on the morphology, welding depth and width as well as quality of the welded seam were investigated. Results show that full keyhole welding is not formed on both K4.18 and 42CrMo side, simultaneously, due to the relatively low output power. Partial fusion is observed on the welded seam near 42CrMo side because of the large disparity of thermal-physical and high-temperature mechanical properties of these two materials. Tile rnicrohardness of the laser-welded joint was also examined and analyzed. It is suggested that applying negative defocusing in the range of Raylei length can increase the welding depth and improve tile coupling efficiency of the laser materials interaction. (c) 2007 Elsevier Ltd. All rights reserved.