X.F. Liu

Design and fabrication of low beam divergence and high kink-free power lasers

We report the design and fabrication of high performance high power lasers with emission wavelength from 800 to 1000 nm using a novel wafer structure, in which a graded V-shape layer was incorporated, to reduce the vertical far field (wafer growth direction) and to suppress higher order mode lasing. The structure offers the freedom to independently design the vertical far field and optical overlap with the quantum wells. An extremely low far field can be achieved, which still retains high optical overlap, allowing a low threshold current to be maintained. In addition, the structure can greatly enhance the laser kink-free power by suppressing or even completely eliminating higher order mode lasing, an extremely desirable property for high power single mode lasers.

Monolithic fabrication of 2 /spl times/ 2 crosspoint switches in InGaAs-InAlGaAs multiple quantum wells using quantum-well intermixing

In this letter, we report the fabrication of 2 /spl times/ 2 crosspoint switches, which monolithically integrate passive waveguides, electro-absorption modulators and optical amplifiers onto one chip using sputtered SiO/sub 2/ quantum-well intermixing technique. The switches have low insertion loss to be about 4-5 dB and extinction ratios up to 26 dB.

Control of multiple bandgap shifts in InGaAs-AlInGaAs multiple-quantum-well material using different thicknesses of PECVD SiO 2 protection layers

A useful development of the sputtered SiO/sub 2/ intermixing technique is reported, which uses a single stage of sputtered SiO/sub 2/ deposition and annealing to achieve precise tuning of the bandgap energy in the InGaAs-AlInGaAs material system. The blue shift of photoluminescence spectra can be varied in the range of 0-160 nm. Bandgap-tuned lasers were integrated on a single chip using this technique to assess the post-processed material characteristics and demonstrate its application in optoelectronic integration.

Design and fabrication of low beam divergence and high kink-free power 980 nm lasers

We report on the design and fabrication of high power 980 nm single mode lasers using a novel wafer structure, which leads to a greatly enhanced kink-free power and low beam divergence.

Benefits of quantum well intermixing in high power diode lasers

Quantum well intermixing (QWI) can bring considerable benefits to the reliability and performance of high power laser diodes by intermixing the facet regions of the device to increase the band-gap and hence eliminate absorption, avoiding catastrophic optical damage (COD). The non-absorbing mirror (NAM) regions of the laser cavity can be up to ~20% of the cavity length, giving an additional benefit on cleave tolerances, to fabricate very large element arrays of high power, individually addressable, single mode lasers. As a consequence, large arrays of single mode lasers can bring additional benefits for packaging in terms of hybrization and integration into an optics system. Our QWI techniques have been applied to a range of material systems, including GaAs/AlGaAs, (Al)GaAsP/AlGaAs and InGaAs/GaAs.

Fabrication of monolithically integrated Mach-Zehnder asymmetric interferometer switch

We report a novel method of fabricating a compact, monolithically integrated AlInGaAs Mach-Zehnder asymmetric interferometer for use as a 40 Gbit/s demultiplexer. Instead of regrowth, the plasma process damage induced quantum well intermixing was used to modify the bandgap of passive waveguides.

High reliability, high power arrays of 808 nm single mode diode lasers employing various quantum well structures

Single mode laser diode arrays operating at 808 nm have been designed and fabricated using several different waveguide and quantum well combinations. In order to operate these devices at 200 mW per element a quantum well intermixing process has been used to render their facets non-absorbing and thus they do not suffer from mirror damage related failure. In this paper we demonstrate extremely high levels of reliability for GaAs and AlGaAs quantum well devices with arrays of 64 elements completing over 6000 hours continuous operation without any single laser element failure and a correspondingly low power degradation rate of <1% k/hr. In contrast we show extremely high power degradation rates for arrays using InGaAs and InAlGaAs 808 nm quantum wells laser arrays.

Recent developments in QCW bar and stacks fabricated with QWI enhanced bars

In this paper we have shown the application of QWI to the fabrication of QCW laser bars. Extended reliability has been shown as well as the recent development of higher power bars and stacks.

Integration of passive waveguides using quantum well intermixing to produce reliable 980 nm laser diodes

Quantum well intermixing (QWI) of the facet regions of 980 nm AlGaInAs lasers significantly improves the high temperature performance and reliability of the laser. The passive non-absorbing regions also improve the single-mode stability of the device at high temperature.

The application of a novel intermixing technique for multi-bandgap integration of InGaAs/AlInGaAs

Here, for the first time, we report the application of this novel technique to a dual wavelength ridge waveguide laser array and an integrated 2x2 cross point optical switch in InGaAs-AlInGaAs material. In the fabrication, a cap layer of 200 nm of PECVD SiO/sub 2/ was deposited onto InGaAs-AlInGaAs multi-quantum-well samples.