A review on the recent developments in the field of long-wavelength (A > 1.2 μm) high-brightness optically-pumped semiconductor disk lasers (OPSDLs) is presented. As thermal effects have such a crucial impact on the laser performance particular emphasis is given to modelling the thermal behaviour and optimisation of the heat-sinking. Selected OPSDL devices, realized in different III-V and IV-VI semiconductor material systems, with corresponding emission wavelengths between 1.2 μm and 5.3 μm are presented. Specific applications in this broad spectral range are addressed and methods to obtain high output power are discussed in terms of the underlying material properties and device operating principles.

High-brightness long-wavelength semiconductor disk lasers

In the past few years, GaInNAsSb has been found to be a potentially superior material to both GaInNAs and InGaAsP for communications wavelength laser applications. It has been observed that due to the surfactant role of antimony during epitaxy, higher quality material can be grown over the entire 1.2 – 1.6 µm range on GaAs substrates. In addition, it has been discovered that antimony in GaInNAsSb also works as a constituent that significantly modifies the valence band. These findings motivated a systematic study of GaInNAsSb alloys with widely varying compositions. Our recent progress in growth and materials development of GaInNAsSb alloys and our fabrication of 1.5 – 1.6 µm lasers are discussed in this paper. We review our recent studies of the conduction band offset in (Ga,In) (N,As,Sb)/GaAs quantum wells and discuss the growth challenges of GaInNAsSb alloys. Finally, we report record setting long wavelength edge emitting lasers and the first monolithic VCSELs operating at 1.5 µm based on GaInNAsSb QWs grown on GaAs. Successful development of GaInNAsSb alloys for lasers has led to a much broader range of potential applications for this material including: solar cells, electroabsorption modulators, saturable absorbers and far infrared optoelectronic devices and these are also briefly discussed in this paper.

Development of GaInNAsSb alloys : Growth, band structure, optical properties and applications

The 1.55 /spl mu/m pulsed operation of an optically-pumped GaInNAsSb vertical-cavity surface-emitting laser (VCSEL) is reported. The structure employs a dielectric (SiO/sub 2//TiO/sub 2/) top mirror, while the bottom mirror and active region were grown on GaAs by MBE. Temperature-dependent (10-40/spl deg/C) laser measurements were made for an as-grown sample and an annealed sample, both having a room-temperature lasing wavelength of 1547 nm. Results indicate an annealing-induced blue-shift of the gain peak.

C-band emission from GaInNAsSbVCSEL on GaAS

The origin of the degradation with N of the threshold current density (Jth) and external differential quantum efficiency (ηd) of 1.29 to 1.52μmGaInNAs∕GaAs laser diodes is analyzed. Adding N to InGaAs leads to a ∼25% reduction of the carrier injection efficiency and thus to an increase of Jth and a decrease of ηd. This effect is likely related to carrier recombination losses in the barriers and is independent of the N content. The optical absorption losses and the internal transparency current density are found to increase with N content, accounting for the rest of the degradation in Jth. Modeling of the transparency carrier and radiative current densities identifies the increase of the defect-related recombination coefficient in GaInNAs as the dominant effect leading to the N dependence of Jtr.

Impact of N on the lasing characteristics of GaInNAs∕GaAs quantum well lasers emitting from 1.29 to 1.52μm

The continuous-wave (cw) operation of GaInNAsSb lasers at 1560nm is reported. Light-current measurements were made before and after a 100h cw burn in at 20°C, during which a 3×890μm2 device with 72mA initial threshold current and 14mW maximum output power experienced a 15% drop in peak output power. These preliminary lifetime results provide insight into the reliability of GaInNAsSb active regions and reinforce the promise of this material for C-band devices. High-resolution modal gain spectra were extracted from the amplified spontaneous emission spectra acquired after the burn in, providing reliable values for the internal loss, transparency current, and differential gain.

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Gain and lifetime of GaInNAsSb narrow ridge waveguide laser diodes in continuous-wave operation at 1.56μm

(Ga,In)(N,As)/GaAs single quantum well lasers have been grown by molecular beam epitaxy. Room temperature pulsed operation at a wavelength of 1515 nm is achieved. As-cleaved 1000 /spl mu/m-long lasers have a threshold current density of 4.06 kA/cm/sup 2/ and a slope efficiency of 0.075 W/A per facet.

J.-M. Ulloa

Papers

Performance improvement of 1.52 [micro sign]m (Ga,In)(N,As)/GaAs quantum well lasers on GaAs substrates