S. H. Groves

Low‐threshold InGaAs strained‐layer quantum‐well lasers (λ=0.98 μm) with GaInP cladding layers and mass‐transported buried heterostructure

Buried‐heterostructure quantum‐well lasers fabricated by mass transport are reported for In0.18Ga0.82As/GaAs/Ga0.5In0.5P strained‐layer structures grown by atmospheric pressure organometallic vapor‐phase epitaxy. Threshold current densities as low as 85 A/cm2 are measured for broad‐stripe lasers, and buried‐stripe devices show threshold currents as low as 3 mA and differential quantum efficiencies as high as 34% per facet without coatings.

Double‐heterostructure PbSnTe lasers grown by molecular‐beam epitaxy with cw operation up to 114 K

Double‐heterostructure Pb1−xSnxTe lasers with active regions of Pb0.782Sn0.218Te have been grown by molecular‐beam epitaxy which operate cw up to heat‐sink temperatures of 114 K. Temperature tuning of the emission from 15.9 to 8.54 μm wavelength is obtained, with emission at 77 K near 11.5 μm. The current‐voltage characteristics show an abrupt change in slope at threshold, indicating high incremental internal quantum efficiency.

InGaAsP/InP avalanche photodiodes for photon counting at 1.06 μm

Geiger-mode (photon-counting) operation at 1.06 μm has been demonstrated with InGaAsP/InP avalanche photodiodes operated at room temperature. A photon detection efficiency of 33% was measured on uncoated detectors, representing an internal avalanche probability of 60%. Under identical bias conditions a dark count rate as low as 1.7 MHz was measured at 290 K, consistent with a primary dark current of <0.3 pA. Dark count rates drop by approximately 50–200× by cooling the detectors to 210 K (−63 °C).

40-Gbit/s all-optical circulating shift register with an inverter.

We report what is believed to be the first demonstration of an all-optical circulating shift register using an ultrafast nonlinear interferometer with a polarization-insensitive semiconductor optical amplifier as the nonlinear switching element. The device operates at 40 Gbits/s, to our knowledge the highest speed demonstrated to date. Also, the demonstration proves the cascadability of the ultrafast nonlinear interferometric switch.

Afterpulsing in Geiger-mode avalanche photodiodes for 1.06μm wavelength

We consider the phenomenon of afterpulsing in avalanche photodiodes (APDs) operating in gated and free-running Geiger mode. An operational model of afterpulsing and other noise characteristics of APDs predicts the noise behavior observed in the free-running mode. We also use gated-mode data to investigate possible sources of afterpulsing in these devices. For 30-μm-diam, 1.06-μm-wavelength InGaAsP∕InP APDs operated at 290K and 4V overbias, we obtained a dominant trap lifetime of τd=0.32μs, a trap energy of 0.11eV, and a baseline dark count rate 245kHz.

Slab-coupled 1.3-μm semiconductor laser with single-spatial large-diameter mode

A high brightness semiconductor diode laser structure, which utilizes a slab-coupled optical waveguide region to achieve several potentially important advances in performance, is proposed and experimentally demonstrated using a simple rib waveguide in an InGaAsP-InP quantum-well structure operating at 1.3-/spl mu/m wavelength. These lasers operate in a large low-aspect-ratio lowest-order spatial mode, which can be butt coupled to a single-mode fiber with high coupling efficiency.

1.5-μm tapered-gain-region lasers with high-CW output powers

High-power diode lasers consisting of a a tapered region have waveguide section coupled to fabricated in 1.5-/spl mu/m InGaAsP-InP multiple-quantum-well material. Self-focusing at high current densities and high intensity input into the taper section has been identified as a fundamental problem in these devices that has to be dealt with. To date, continuous-wave output powers of >1 W with /spl ap/80% of the power in the near-diffraction-limited central lobe of the far field have been obtained through a judicious choice of device parameters.

Diffraction-limited 1.3-μm-wavelength tapered-gain-region lasers with >1-W CW output power

Diode lasers have been fabricated in InGaAsP-InP multiple-quantum-well material grown by atmospheric-pressure organometallic vapor-phase epitaxy with an active optical cavity consisting of a ridge-waveguide region coupled to a tapered gain region. Over 1 W of CW output power was obtained with 85% of the power in the central lobe of a diffraction-limited far-field radiation pattern.

GaInP mass transport and GaInP/GaAs buried‐heterostructure lasers

Mass transport of a semiconductor alloy has been demonstrated using Ga0.51In0.49P which is lattice matched to GaAs. Buried‐heterostructure diode lasers with Ga0.51In0.49P as cladding and GaAs as the active layer have been made using this fabrication technique. Initial attempts produce devices with room‐temperature lasing thresholds of ∼33 mA and 15% differential power efficiency per facet.

Distributed feedback Pb1−xSnxTe double‐heterostructure lasers

Distributed feedback laser operation is demonstrated in stripe‐geometry Pb1−x Sn x Te double heterostructuresgrown by molecular‐beam epitaxy. The grating of 1.1 μm periodicity operates in first order near 745 cm−1 (13.4 μm) under pulsed conditions in a limited range of heat‐sink temperatuers (∼30–65 K) where both gain and the Bragg reflection condition can be achieved. The guide index n g ≃6.1 is consistent with theoretical estimates. In Pb1−x Sn x Te DH devices, by corrugating the surface after all epitaxy is completed, a large coupling coefficient for Bragg reflection can be achieved because the last confining layer can be made very thin and the grating aspect ratio large.