Paul Salet

1-mW CW-RT monolithic VCSEL at 1.55 μm

In this letter, we demonstrate the first result of a high-power (1 mW) continuous-wave room-temperature vertical-cavity surface-emitting laser emitting at 1.55 /spl mu/m using a single InP substrate. The whole structure was grown monolithically using gas source molecular beam epitaxy and incorporates two original approaches. The first originality consists in the growth of a metamorphic GaAs-AlAs Bragg mirror directly on an InP-based cavity. The second novel idea is to use a tunnel junction for current injection. Moreover by using these two approaches the processing is very simple and, therefore, fulfills the goal for low-cost laser production in access and interconnections applications.

1.1-W continuous-wave 1480-nm semiconductor lasers with distributed electrodes for mode shaping

Diffraction-limited high-power devices may suffer from self-focusing effects due to nonuniform gain saturation. In this letter, we propose the concept of the distributed electrode, which allows one to improve the modal behavior of these lasers and to reduce spatial-hole burning effects by preferentially localizing current injection in the center of the structure, therefore shaping the optical mode. Utilizing this concept, we have realized unstable cavity lasers exhibiting single-lobe far-field patterns. We report the first realization of flared unstable cavity lasers emitting at 1480 mm with maximum output powers up to 1.1-W continuous-wave and external efficiencies as high as 0.45 W/A.

Numerical modeling of undercut ridge VCSELs designed for CW operation at 1.3 /spl mu/m: design optimization

Optimized undercut ridge long-wavelength vertical-cavity surface-emitting semiconductor lasers (LW-VCSELs) are investigated and the influence of thermal effects on the light versus current characteristics is analyzed by thermal-electric, optical, and electronic modeling. The model includes nonuniform current injection, carrier diffusion, stimulated emission, distributed heat sources, and active material band structure calculations. Device parameters such as thermal resistance, threshold current, and external quantum efficiency are evaluated, in an attempt to provide an understanding of the current-funneling mechanism and the thermal limitations of such devices. Simulated power versus current characteristics exhibit the typical thermal roll-over in CW operation.

Single transverse-mode filtering utilizing ion implantation: application to 1.48-μm unstable-cavity lasers

We demonstrate the relevance of ion implantation of the multiple quantum-well active layer in unstable-cavity lasers as a means of efficiently filtering the parasitic higher order waves by introducing additional propagation loss within the cavity. Several H/sup +/ implantation schemes are proposed and a comparison is successfully made of experiment to a beam propagation method (BPM) model on the basis of modal behavior. The work finally resulted in improved single transverse-mode behavior of those lasers: more than 1.3 W CW of diffraction-limited power at 1.48 /spl mu/m was then obtained utilizing a two-step implantation process.

1 mW CW RT 1.55 /spl mu/m tunnel VCSEL: thermal and electrical characteristics of GaAs/AlAs metamorphic mirrors

Summary form only given. Recently, high power monolithic VCSELs (1 mW at 1.55 um) have been demonstrated by using tunnel junction injection and a metamorphic AlAs/GaAs mirror. This approach combined with a planar process based on proton implantation might enable the ultra low cost fabrication of 1.55 /spl mu/m laser sources. In the paper we present the optimization of the electrical conductivity of AlAs/GaAs n type metamorphic mirrors and analyze their thermal properties.

Single-transverse-mode filtering utilizing proton implantation: 1.3-W CW diffraction-limited unstable-cavity lasers at 1.48 /spl mu/m

We report the realization of a lossy filter utilizing ion implantation of the multiple-quantum-well (MQW) active layer along both sides of the ridge waveguide, and optimize the implantation process so as to enhance the diffraction-limited power level of our 1.48-μm unstable-cavity lasers. This enables at least 1.3 W of CW diffraction-limited power at 1.48 μm, which is the highest level ever reported for a structure without cavity-spoiling grooves.

Tolerant low-loss three-lens coupling system for 1.48-μm unstable-cavity lasers

A 1.48-/spl mu/m unstable-cavity laser is coupled into single-mode fiber using three microlenses. Reproducible coupling of very high power is demonstrated with different types of lenses (plano-convex or biconvex, with different apertures). Over 550 mW in single-mode fiber (SMF) were reproducibly reached; to our knowledge, it is the highest power coupled into an SMF from a single semiconductor laser at this wavelength. Tolerance measurements on all of the coupling elements of a three-lens system are reported for the first time; an unexpected very large tolerance an the axial displacement of the second lens was measured. Results and interpretation with the aid of Gaussian and aberration simulations are also presented.

1.1-W continuous-wave 1480-nm unstable-cavity lasers with distributed electrodes for mode shaping

The distributed electrode enables to reduce spatial hole-burning effects, therefore improving the modal behavior of diffraction-limited MQW lasers. We report the first realization of such devices emitting 1.1 W nearly single mode at 1480 nm.

Fabrication of 1.55 /spl mu/m oxidized VCSELs with top metamorphic GaAs/GaAlAs and bottom InP/InGaAsP Bragg reflectors

We present the fabrication of 1.55 /spl mu/m multi-quantum well vertical cavity surface emitting lasers (VCSEL) grown by gas source MBE on InP substrate. We use a combination of lattice-matched InP/InGaAsP and GaAs/GaAlAs metamorphic reflectors with high reflectivities. Room temperature operation in pulsed mode is achieved. We also demonstrate that selective wet oxidation of GaAlAs can be applied to metamorphic material.

Numerical modeling of long-wavelength vertical-cavity surface-emitting semiconductor lasers. I. Continuous-wave modeling

Long-wavelength vertical-cavity surface-emitting semiconductor lasers are investigated and heating effects on the light vs. current characteristics of VCSELs are analyzed by thermal-electric, optical, and electronic modeling. The model includes nonuniform current injection, carrier diffusion, stimulated emission, distributed heat sources, and active material band structure calculations. Device parameters such as threshold current, and external quantum efficiency are evaluated. Simulated power vs. current characteristics exhibit the typical thermal roll-over in continuous wave operation. The model is applied to two specific optimized underetched structure designs in order to provide an understanding of the current-funneling mechanism and the thermal limitations of such devices.