AlGaAs/GaAs visible ridge waveguide laser with multicavity structure

Ridge waveguide lasers of two different cavity configurations are described. First is the multisection ridge laser structure in which the longitudinal mode selection due to the coupled-cavity effect was observed and single-frequency operation was achieved. In this structure, stable single-transverse-mode operation was ensured by the central 5 μm wide section, and the beam waist and power output were enlarged by the outer 10 μm wide sections. Output power of more than 13 mW under pulsed excitation was obtained. The second configuration is the shallow groove ridge laser in which the 5 μm wide shallow groove terminates slightly above the active region and provides an index perturbation that contributes to mode selection. All the lasers are designed to emil in the visible range between 7600 and 7900 Å. The shortest observed wavelength is 7570 Å, and can be seen by the naked eye.     

GaAs/AlGaAs rooftop reflector laser for optoelectronic integrated circuits

A GaAs/AlGaAs laser, consisting of a cleaved facet and a chemically etched total-internal-reflecting rooftop reflector, is fabricated and tested. The results show that the rooftop reflector with the reflectivity exceeding 0.9 can be readily obtained and the laser is suitable for optoelectronic integrated circuits.     

Novel fabrication-tolerant twin-guide laser structure with anexternal passive waveguide

The authors propose a novel quasi-symmetrical twin-guide GaAs/AlGaAs laser structure (QSTGL) with a low-loss external passive waveguide. The device is tolerant to fabrication misalignment and therefore well suited for monolithic integration. Threshold current densities of less than 1.1 kA/cm² and a coupling efficiency between 70 and 80% into the low-loss passive waveguide are achieved     

7.4 Gbit monolithically integrated GaAs/AlGaAs laser diode-laser driver structure

A molecular beam epitaxy (MBE) grown GaAs/AlGaAs multiquantum well laser, monolithically integrated with a laser driver was realised on 2 inch GaAs substrate wafers. In an optical data communication set up, performance up to data rates of 7.4 Gbit/s was demonstrated.<>     

AlGaAs/GaAs microcleaved facet (MCF) laser monolithically integrated with photodiode

A new AlGaAs/GaAs double-heterostructure laser with microcleaved facets, restricted just at stripe contact edges, has been developed. This laser and a junction photodiode have been monolithically integrated in a single GaAs substrate. Low-threshold current lasing and high-fidelity monitoring characteristics have been demonstrated.     

Monolithically integrated optical gate 2 × 2 matrix switch using GaAs/AlGaAs multiple quantum well structure

A 2 × 2 optical matrix switch, monolithically integrating multiple-quantum-well-gate and optical circuits fabricated by the reactive-ion-beam etching method, is described. The switch size is small, 3 mm × 1.2 mm. Low crosstalk of 20 dB at 12 V is achieved.     

TE-to-TM mode conversion in GaAs/AlGaAs superlattice waveguide

Intrinsic phase matching between a TE and a TM mode is obtained in a GaAs/AlGaAs superlattice waveguide, fabricated by Zn diffusion induced disordering, as a result of the birefringent waveguiding properties of the superlattice in combination with a proper choice of the waveguide geometry. As a consequence, up to 90% polarisation conversion is demonstrated without the application of phase matching techniques.<>     

Ridge waveguide AlGaAs/GaAs distributed feedback lasers

Ridge waveguide AlGaAs/GaAs distributed feedback lasers were fabricated by a two-step molecular beam epitaxy. A threshold current as low as 37 mA, which is the lowest ever reported, was obtained under a continuous wave condition at room temperature. The low threshold current is due to the larger coupling coefficient (91 cm^-1) and a good current and optical confinement. The effects of the facet coatings were investigated and a high-power and a high-temperature operation was obtained. The polarization and the dynamic behavior were also investigated.     

Fabrication of an optoelectronic AlGaAs/GaAs waveguide neuron

A novel optical waveguide neuron is fabricated. It accepts two inputs, applies adjustable weights to them, sums the weighted inputs, and thresholds the sum to issue one output. An AlGaAs/GaAs p-i-n diode waveguide with a Wannier-Stark superlattice in the core is used. Two modulators and one saturable absorber are monolithically integrated on a 5-μm rib waveguide Y-junction combiner. A simple self-aligned single-mask liftoff technique with wet chemical etching is used. At 780 nm the weights vary from 1 to -25 dB/mm for reverse bias below 7 V, and a 25-dB thresholding nonlinearity is obtained     

Four-junction AlGaAs/GaAs laser power converter

Four-junction A1GaAs/GaAs laser power converters (LPCs) with n+-GaAs/p+-Al0.37Ga0.63As heterostructure tunnel junctions (TJs) have been designed and grown by metal-organic chemical vapor deposition (MOCVD) for converting the power of 808 nm lasers.A maximum conversion efficiency ηc of 56.9％ + 4％ is obtained for cells with an aperture of 3.14 mm2 at an input laser power of 0.2 W,while dropping to 43.3％ at 1.5 W.Measured current-voltage (I-V) characteristics indicate that the performance of the LPC can be further improved by increasing the tunneling current density of TJs and optimizing the thicknesses of sub-cells to achieve current matching in LPC.     

Wavelength dependence of high-performance AlGaAs/GaAs waveguide phase modulators

The wavelength dependence of doped, reverse-biased channel waveguide phase modulators with very high efficiencies are reported between 1.06 ?m and 1.53 ?m. Figures-of-merit ranging from 61°/V mm and 40°/V mm to 27°/V mm and 16°/V mm for the TE and TM modes, respectively, have been obtained. By deducting the easily calculated linear electro-optic and free-carrier plasma effects, the data gives the first real measure of the dispersion associated with the shift in the absorption edge. This dispersion, which is the primary contribution to the quadratic electro-optic effect in semiconductors, accounts for more than half of the measured phase shift at 1.06 ?m with the doping level used.     

Fabrication of a terahertz quantum-cascade laser with a double metal waveguide based on multilayer GaAs/AlGaAs heterostructures

The Postgrowth processing of GaAs/AlGaAs multilayer heterostructures for terahertz quantumcascade lasers (QCLs) are studied. This procedure includes the thermocompression bonding of In–Au multilayer heterostructures with a doped n⁺-GaAs substrate, mechanical grinding, and selective wet etching of the substrate, and dry etching of QCL ridge mesastripes through a Ti/Au metallization mask 50 and 100 μm wide. Reactive-ion-etching modes with an inductively coupled plasma source in a BCl₃/Ar gas mixture are selected to obtain vertical walls of the QCL ridge mesastripes with minimum Ti/Au mask sputtering.     

Spectral linewidth of AlGaAs/GaAs surface-emitting laser

The spectral linewidth Delta nu of a vertical cavity surface-emitting (SE) laser was measured for the first time. The linewidth measured by a delayed self-homodyne method was 50 MHz at an output power of 1.4 mW under room-temperature CW operation. The linewidth obtained was guite narrow in spite of the short cavity configuration of the SE laser. This narrow linewidth is attributed to the high-reflectivity mirrors. The measured linewidth is in good agreement with theoretical values.<>     

Monolithically integrated multiwavelength grating cavity laser

A multiwavelength grating cavity laser is reported using a novel design for a multichannel light source based on an etched diffraction grating. Following the design, the compact eight-channel device capable of fine-tuning has been realized by monolithically integrating semiconductor optical amplifiers, various passive waveguides, and deeply etched grating, providing high butt-coupling efficiency, and low waveguide losses. As a result, the sidemode suppression ratio in excess of 45 dB over all channels was achieved.     

Transform-limited picosecond optical pulses from a mode-lockedInGaAs/AlGaAs QW laser with integrated passive waveguide cavity and QWmodulator

Using a novel single-top molecular beam epitaxy growth technology on nonplanar substrates, an InGaAs/AlGaAs laser amplifier has been integrated with a 4-mm-long passive waveguide cavity and a QW modulator. Lasing action of the entire structure was achieved by a current of 60 mA flowing through the amplifier section. Mode-locking experiments in which an RF signal was applied to the modulator segment led to nearly-transform-limited pulses with a duration of 4.4 ps and a time-bandwidth product of 0.43     

MOCVD-grown InGaAs/GaAs/AlGaAs laser structures with a broad-area contact

A metal-organic chemical vapor deposition (MOCVD) technique is developed for a diode laser heterostructure in a system of InGaAs/GaAs/AlGaAs solid solutions; the optimal sizes and the doping profile of the structure are determined to minimize the internal optical losses. Mesa-strip diode lasers with a threshold density of current J _th=150–200 A/cm², internal optical loss factor α_i=1.6–1.9 cm^?1, and an internal quantum yield η_i=85–95% were fabricated. In the continuous lasing mode of a diode laser with a 100-µm-wide aperture and a wavelength of 0.98 µm, the optical power output was as high as 6.5 W and was limited by the catastrophic optical degradation of mirrors. The radiation divergence in the plane normal to the p-n junction amounts to θ_⊥. The use of wide-gap waveguide layers, which deepens the potential electron well in the active region, is shown to reduce the temperature sensitivity of the InGaAs/GaAs/AlGaAs laser heterostructures in the temperature range from 0 to 70°C.     

AlGaAs/GaAs multiquantum-well (MQW) surface-emitting laser

In the letter the lasing characteristics of a multiquantum-well surface-emitting injection laser with 100 wells at 77 K under pulsed condition is reported. The output light of the device was linearly polarised.<>     

Implanted-planar-buried-heterostructure, graded-index,separate-confinement-heterostructure laser in GaAs/AlGaAs

For the implanted planar buried-heterostructure, graded-index, separate-confinement-heterostructure (IPBH-GRINSCH) laser in (AlGa)As/GaAs, ion implantation is used to form p-n-p-n current blocking layers and to create a buried-heterostructure waveguide. This results in significantly reduced fabrication complexity of high-quality, index-guided laser diodes compared to regrowth techniques, and in contrast to diffusion-induced disordering, allows for the creation of self-aligned, buried, blocking junctions. Kink-free, CW operation of single-stripe IPBH-GRINSCH lasers along with single-lobed near-field and far-field optical emission patterns, consistent with index-guided operation, is demonstrated     

Optoelectronic integrated four-channel transmitter arrayincorporating AlGaAs/GaAs quantum-well lasers

A four-channel optoelectronic integrated transmitter array which is fabricated on a single GaAs substrate and operates at 834 nm is described. Each of the circuits incorporates a laser, a photodiode for laser power monitoring, and a laser driver circuit consisting of three GaAs field-effect transistors and a resistor. Laser threshold current of 15-21 mA, transmitter conversion efficiency of approximately 6 mW/V and high-speed operation at a bit rate of more than 1.5-Gb/s NRZ with allowable crosstalk have been demonstrated. A preliminary aging test of the lasers indicated that their stability is comparable to that of discrete devices. The results have demonstrated the feasibility of applying the transmitter array to optical components that process multichannel optical signals at high speed