Maolong Ke

Monolithic integration via a universal damage enhanced quantum-well intermixing technique

A novel technique for quantum-well intermixing is demonstrated, which has proven a reliable means for obtaining postgrowth shifts in the band edge of a wide range of III-V material systems. The technique relies upon the generation of point defects via plasma induced damage during the deposition of sputtered SiO/sub 2/, and provides a simple and reliable process for the fabrication of both wavelength tuned lasers and monolithically integrated devices. Wavelength tuned broad area oxide stripe lasers are demonstrated in InGaAs-InAlGaAs, InGaAs-InGaAsP, and GaInP-AlGaInP quantum well systems, and it is shown that low absorption losses are obtained after intermixing. Oxide stripe lasers with integrated slab waveguides have also enabled the production of a narrow single lobed far field (3/spl deg/) pattern in both InGaAs-InAlGaAs, and GaInP-AlGaInP devices. Extended cavity ridge waveguide lasers operating at 1.5 /spl mu/m are demonstrated with low loss (/spl alpha/=4.1 cm/sup -1/) waveguides, and it is shown that this loss is limited only by free carrier absorption in waveguide cladding layers. In addition, the operation of intermixed multimode interference couplers is demonstrated, where four GaAs-AlGaAs laser amplifiers are monolithically integrated to produce high output powers of 180 mW in a single fundamental mode. The results illustrate that the technique can routinely be used to fabricate low-loss optical interconnects and offers a very promising route toward photonic integration.

Monolithically integrated fabrication of 2/spl times/2 and 4/spl times/4 crosspoint switches using quantum well intermixing

We report the fabrication of 2/spl times/2 and 4/spl times/4 crosspoint switches, in which semiconductor optical amplifiers, electro-absorption modulators, and passive waveguides were monolithically integrated on one chip, using sputtered SiO/sub 2/ for quantum well intermixing. The static performance of the 2/spl times/2 switches was assessed, with the extinction ratio of the modulator being 25 dB for a reverse bias of 2 V, and inter-channel crosstalk being better than -23 dB. The gain of the amplifiers is about 8 dB.

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.

Monolithically integrated distributed Bragg reflector lasers for 1.5 μm operation with band gap shifted grating section

The design and operation of long wavelength ridge waveguide distributed Bragg reflector lasers in both InGaAs–InGaAlAs and InGaAs–InGaAsP materials with deeply dry-etched surface gratings are presented. To our knowledge, quantum well intermixing was used for the first time in these systems to widen the band gap in the grating region, and significant improvement in performance is obtained from the distributed Bragg reflector (DBR) lasers with intermixed grating region.

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

Summary form only given. Optical switching and packet routing are highly desirable functions in optical communication networks. The requirements of both a high switching speed and low insertion loss can be met using semiconductor devices. Here we report the monolithic integration of semiconductor optical amplifiers (SOAs), electro-absorption (EA) modulators, and passive power splitters and combiners to form 2 /spl times/ 2 crosspoint switches.

EXTENDED CAVITY LASERS IN INGAAS-INGAASP AND GAINP-ALGAINP MULTI-QUANTUM WELL STRUCTURE USING A SPUTTERED SIO2 TECHNIQUE

Sputtering a thin layer of SiO2 (≈200 nm) followed by high temperature annealing has recently been found to be very promising in promoting quantum well intermixing. The intermixing is thought to be due to point defects generated by the sputtering plasma diffusing through the material during a subsequent high temperature anneal. In this paper, we describe the technique using the sputtered SiO2 and subsequent high temperature annealing, either by rapid thermal Annealer (RTA) or CW Nd:YAG laser operated at 1.064 µm. Differential blue shifts of up to 70 meV and 120 meV have been obtained for InGaAs-InGaAsP and GaInP-AlGaInP material systems. Extended cavity lasers have been fabricated and characterised for both material systems.

Monolithic integration in III-V semiconductors via a universal damage enhanced quantum well intermixing technique

A novel technique for quantum well intermixing is demonstrated which has proven to be a reliable means for obtaining post-growth shifts in the band edge of a wide range of III-V material systems. The techniques relies upon the generation of point defects via plasma induced damage during the deposition of sputtered silica, and provides a simple and reliable process for the fabrication of both wavelength tuned lasers and monolithically integrated devices. Wavelength tuned board area oxide stripe lasers are demonstrated in InGaAs-InAlGaAs, InGaAs-InGaAsP, and GaInP- AlInP quantum well systems, and it is shown that low absorption losses are obtained after intermixing. Oxide stripe lasers with integrated slab waveguides have also enabled the production of a narrow single lobed far field pattern in both InGaAs-InAlGaAs, and GaInP-AlGaInP devices. Extended cavity ridge waveguide lasers operating at 1.5 micrometers are demonstrated with low loss waveguides, and it is shown that this loss is limited only by free carrier absorption in the waveguide cladding layers. In addition, the operation of intermixed multi-mode interference coupler lasers is demonstrated, where four GaAs-AlGaAs laser amplifiers are monolithically integrated to produce high output powers of 180 mW in a single fundamental mode. The results illustrate that the technique can routinely be used to fabricate low los optical interconnects and offers a very promising route toward photonic integration.

Fabrication of a monolithic 2 /spl times/ 2 crosspoint switches in an InGaAs/InAlGaAs multiple quantum well structure using quantum well intermixing

Summary form only given. We report on the fabrication and assessment of 2 /spl times/ 2 crosspoint switches based on EA modulators using the quantum well intermixing (QWI) approach. The peak wavelengths of room temperature photoluminescence (PL) were 1520 nm, 1480 nm, and 1410 nm for the amplifier sections, modulator sections, and passive sections respectively after intermixing.

InGaAlAs-InP ridge waveguide distributed Bragg reflector lasers with deeply dry-etched surface gratings

Summary form only given. Distributed Bragg reflector (DBR) lasers have potential advantages over distributed feedback (DFB) lasers due to the fact that the separation of the active gain section from the passive grating section can lead to lower chirp and better temperature stability. Utilising surface gratings to fabricate DBR lasers avoids the problems of regrowth, and surface gratings have recently been used to fabricate DBR lasers in the InGaAsP-InP material system for operation at 1.5 /spl mu/m. We here report 1.5 /spl mu/m surface grating DBR lasers fabricated in InGaAlAs-InP material as an alternative to InGaAsP-InP system. The InGaAlAs-InP system has a larger conduction band offset (70% /spl Delta/Eg), more efficient electron injection, lower Auger effect and better temperature stability over InGaAs-InP material. Its principal drawback is that suitable fabrication processes are less well developed.

Extended cavity lasers in InGaAs-InGaAsP and InGaAlP-GaAs multi-quantum well structure using a sputtered SiO/sub 2/ technique

Sputtering a thin layer of SiO/sub 2/ (/spl ap/200 nm) followed by high temperature annealing has recently been found to be very promising in promoting quantum well intermixing. The intermixing is thought to be due to point defects generated by the sputtering plasma diffusing through the material during a subsequent high temperature anneal. The process uses simple low-cost techniques, and is extremely reproducible and reliable. In this paper we describe the technique using the sputtered SiO/sub 2/ and subsequent high temperature annealing, either by rapid thermal annealer (RTA) or CW Nd:YAG laser operated at 1.064 /spl mu/m. Differential blue shifts of up to 60 meV and 120 meV have been obtained for InGaAs/InGaAsP and GaInP/AlGaInP material systems. Extended cavity lasers have been fabricated and characterised for both material systems.