C. Caneau

30% External Quantum Efficiency from Surface Textured, Thin-Film Light-Emitting Diodes

There is a significant gap between the internal efficiency of light‐emitting diodes (LEDs) and their external efficiency. The reason for this shortfall is the narrow escape cone for light in high refractive index semiconductors. We have found that by separating thin‐film LEDs from their substrates (by epitaxial lift‐off, for example), it is much easier for light to escape from the LED structure and thereby avoid absorption. Moreover, by nanotexturing the thin‐film surface using ‘‘natural lithography,’’ the light ray dynamics becomes chaotic, and the optical phase‐space distribution becomes ‘‘ergodic,’’ allowing even more of the light to find the escape cone. We have demonstrated 30% external efficiency in GaAs LEDs employing these principles.

Ultrahigh spontaneous emission quantum efficiency, 99.7% internally and 72% externally, from AlGaAs/GaAs/AlGaAs double heterostructures

Optically thin AlGaAs/GaAs/AlGaAs double heterostructures, (5000 A), are floated off their substrates by the epitaxial liftoff technique and mounted on various high reflectivity surfaces. From the absolute photoluminescence intensity, we measure internal and external quantum efficiencies of 99.7% and 72%, respectively. High spontaneous emission quantum efficiency, is important for photon number squeezed light, diode lasers, single‐mode light‐emitting‐diodes, optical interconnects, and solar cells.

Wavelength conversion by difference frequency generation in AlGaAs waveguides with periodic domain inversion achieved by wafer bonding

Wavelength conversion by difference‐frequency generation is achieved in a periodically domain reversed AlGaAs waveguide. The AlGaAs waveguide is epitaxially grown on a template substrate where a periodic crystal domain inversion is achieved using wafer bonding, selective etching, and organometallic chemical vapor deposition. Wavelength conversion experiments on a fabricated buried heterowaveguide showed a 90 nm conversion bandwidth, polarization diversified operation, and polarization independent conversion efficiency. The experimental results also showed linearity and spectral inversion, which imply transparency to signal formats including analog and frequency modulation. Simultaneous conversion of multiple input wavelengths with no measurable cross talk is also demonstrated.

QUASI-PHASE-MATCHED SECOND-HARMONIC GENERATION IN ALGAAS WAVEGUIDES WITH PERIODIC DOMAIN INVERSION ACHIEVED BY WAFER-BONDING

Quasi‐phase‐matched second‐harmonic generation is observed in an AlGaAs waveguide. The AlGaAs waveguide is epitaxially grown on a template substrate where a periodic crystal domain inversion is achieved using wafer bonding and organometallic chemical vapor deposition. A scanning electron micrograph of the waveguide cross section reveals a distinct propagation of the crystal domain boundaries in the epitaxial growth direction. Second‐harmonic generation measurements on a fabricated rib‐loaded waveguide show a clear quadratic dependence of the second‐harmonic power to the input fundamental power. The peak conversion efficiency is 4.9%/W whereas the theoretical value is 124%/W for an ideal waveguide with no loss and with equal domain dimensions. A significant increase in the conversion efficiency is expected with reduced scattering losses realized by improved epitaxial growth and fabrication processes.

Orientation dependence of S,Zn,Si,Te and Sn doping in OMCVD growth of InP and GaAs : application to DH lasers and lateral p-n junction arrays grown on non-planar substrates

Abstract The orientation dependence of doping in organometallic chemical vapor deposition (OMCVD) is shown to be far more complex than previously believed, with the variation of doping with increasing misorientation from (100) towards the (111)A/B being non-monotonic. However, the ratio of the n-doping on the B face to that on the corresponding A face is always greater than 1, irrespective of whether the dopant is a group IV or VI element. For p-doping with Zn, the reverse is true. The orientation dependence of doping has been used to create current blocking layers in InP/InGaAsP double heterostructure (DH) and multiple quantum well (MQW) lasers grown in a single step on a mesa or in a V-groove.

Use of multimode interference couplers to broaden the passband of wavelength-dispersive integrated WDM filters

We describe how multimode interference couplers (MMI) may be used to broaden and flatten the passband of integrated wavelength-dispersive filters. We discuss the approach and demonstrate its effectiveness with a passband-broadened InP arrayed waveguide filter operating at 1.5 /spl mu/m.

InP/GaAsSb/InP and InP/GaAsSb/InGaAsP double heterojunction bipolar transistors with a carbon‐doped base grown by organometallic chemical vapor deposition

InP/GaAsSb double heterojunction bipolar transistors (DHBTs) may be an attractive alternative to InP/InGaAs DHBTs, since estimates of the band alignment indicate that it is ideal for fabricating n‐p‐n DHBTs. We have demonstrated the first organometallic chemical vapor deposition grown InP/GaAsSb DHBTs, with carbon‐doped bases having an ft and fmax of 30 and 45 GHz, respectively.InP/GaAsSb double heterojunction bipolar transistors (DHBTs) may be an attractive alternative to InP/InGaAs DHBTs, since estimates of the band alignment indicate that it is ideal for fabricating n‐p‐n DHBTs. We have demonstrated the first organometallic chemical vapor deposition grown InP/GaAsSb DHBTs, with carbon‐doped bases having an ft and fmax of 30 and 45 GHz, respectively.

Ultracompact monolithic integration of balanced, polarization diversity photodetectors for coherent lightwave receivers

The authors have monolithically integrated an optical front-end on InP for balanced, polarization-diversity coherent lightwave reception which is only 1.3-mm long. Low on-chip insertion loss (<4.5 dB) and balanced photoresponse (1.05:1 or better) are achieved at 1.5- mu m wavelength using straightforward, regrowth-free fabrication. Low-capacitance photodetectors (<or=0.15 pF) are employed for high bandwidth operation.<<ETX>>

Simultaneous Multiple Wavelength Operation of a Multistripe Array Grating Integrated Cavity Laser

Simultaneous multiple‐wavelength operation of a multistripe array grating integrated cavity laser is reported. We demonstrate simultaneous lasing from a single output port at 2, 3, and 4 discrete wavelengths, each independently selected from a comb of 9 wavelengths set at ∼2 nm intervals, from 1512 to 1528 nm. Signal cross talk is examined for the case of two‐wavelength emission and found to be independent of the wavelength separation. The emission wavelengths were linearly spaced to within ±0.02 nm, while the comb’s central wavelength deviated by less than 2 nm from its design value. This is the highest wavelength linearity and accuracy so far recorded for a monolithic multiwavelength source.

Multiwavelength DFB laser array transmitters for ONTC reconfigurable optical network testbed

We discuss the design, fabrication, and performance of experimental multiwavelength laser array transmitters that have been used in the reconfigurable optical network testbed for the Optical Network Technology Consortium (ONTC). The experimental four-node multiwavelength network testbed is SONET/ATM compatible. It has employed multiwavelength DFB laser arrays with 4 nm wavelength spacing for the first time. The testbed has demonstrated that multiwavelength DFB laser arrays are indeed practical and reproducible. For the DFB laser arrays used in such a network the precise wavelength spacing in the array and the absolute wavelength control are the most challenging tasks. We have obtained wavelength accuracy better than /spl plusmn/0.35 nm for all lasers, with some registered to better than /spl plusmn/0.2 nm. We have also studied the array yield of our devices and used wavelength redundancy to improve the array yield. Coupling efficiencies between -2.1 to -4.5 dB for each wavelength channel have been obtained. It is achieved by using specially designed lensed fiber arrays placed on a silicon V-grooved substrate to exactly match the laser spacing. The transmitter consisted of a multichip module containing a DFB laser array, an eight-channel driver array based on GaAs ICs, and associated RF circuitry.