Electroabsorption modulation at 1.3 /spl mu/m on GaAs substrates using a step-graded low temperature grown InAlAs buffer

We have achieved quantum confined Stark effects (QCSE) on In/sub 0.38/Ga/sub 0.62/As-In/sub 0.38/Al/sub 0.62/As multiple-quantum-well (MQW) structures, operating at 1.3 /spl mu/m grown on GaAs substrates. A quantum confined Stark shift of the exciton absorption peak of 47 meV was obtained with an applied electric field of 190 KV/cm, measured on surface normal PIN diodes. The structure is grown by MBE on a novel three-stage, compositionally step graded, In/sub x/Al/sub 1-x/As buffer, doped with Si to 5/spl middot/10/sup 17//cm/sup 3/, on an n-type GaAs substrate. The total thickness of the buffer is 0.3-0.6 mm, which is considerably smaller than that of linearly graded buffer layers. This structure can be used in both waveguide modulators and surface normal F-P type modulators on GaAs substrates.     

High-efficiency 1.3 /spl mu/m InAsP-GaInP MQW electroabsorption waveguide modulators for microwave fiber-optic links

High-efficiency electroabsorption waveguide modulators have been designed and fabricated using strain-compensated InAsP-GaInP multiple quantum wells at 1.32-/spl mu/m wavelength. A typical 200-/spl mu/m-long modulator exhibits a fiber-to-fiber optical insertion loss of 9 dB and an optical saturation intensity larger than 10 mW. The 3-dB electrical bandwidth is in excess of 20 GHz with a 50-/spl Omega/ load termination. When used in an analog microwave fiber-optic link without amplification, a RF link efficiency as high as -38 dB is achieved at 10 mW input optical carrier power. These analog link characteristics are the first reported using MQW electroabsorption waveguide modulators at 1.32 /spl mu/m.     

1.27 /spl mu/m metamorphic InGaAs quantum well lasers on GaAs substrates

Pulsed operation at a wavelength of 1.27 /spl mu/m from metamorphic ridge-waveguide (RWG) InGaAs quantum well lasers on GaAs substrates using an alloy graded buffer, grown by molecular beam epitaxy, is demonstrated. Laser performance is anisotropic along the two orthogonal <1/spl plusmn/10> directions with lower threshold currents along the <1-10> direction. Post-growth rapid thermal annealing further reduces threshold currents. For 4 /spl mu/m-wide RWG lasers, minimum threshold current densities are 1-2.5 kA/cm/sup 2/ for cavity lengths 0.6-1.5 mm.     

Highly reliable 1.3 /spl mu/m InGaAlAs buried-heterostructure laser fabricated with in-situ cleaning

An in-situ-cleaned and regrown 1.3 /spl mu/m InGaAlAs buried-heterostructure laser was fabricated for the first time. The degradation of its driving current was about 1% after a 3000 h aging test. It can thus be concluded from this result that in-situ cleaning is a promising means of fabricating highly reliable, high-performance InGaAlAs BH lasers.     

Quantum dot superluminescent diodes emitting at 1.3 /spl mu/m

We report ridge-waveguide superluminescent diodes based on five stacks of self-assembled InAs-GaAs quantum dots. Devices with output powers up to 10 mW emitting around 1.3 /spl mu/m are demonstrated. Spectral analysis shows a broad emission peak (26-nm full-width at half-maximum) from the dot ground state at low injection, and an additional peak from the excited state at higher bias. Temperature characteristics in the range 10/spl deg/C-80/spl deg/C are also reported. The experimental curves are in good agreement with simulations performed using a traveling-wave rate equation model.     

Reliability analysis of AlGaInAs lasers at 1.3 /spl mu/m

Long-term reliability of 2.5 and 10 Gbit/s 1.3 /spl mu/m AlGaInAs lasers has been demonstrated. Analysis of accelerated life test predicts median life of /spl ges/1.57/spl times/10/sup 6/ h (180 years) at 85/spl deg/C.     

High-quality 1.3-/spl mu/m GaInAsP-BH-lasers fabricated by MOVPE and dry-etching technique

High-quality and high-reliability GaInAsP-InP Fabry-Perot-type buried heterostructure strained-multi-quantum-well lasers operating at 1.3 pm have been produced by metalorganic vapor phase epitaxy growth and the dry-etching technique. We compare two types of chemical treatments to slightly etch damaged mesa-walls before regrowth after dry-etching. Slight chemical etching prevents Zn in the p-type buried layer from diffusing to the active layer during regrowth of buried hetero layers. Two step treatment using the combination of selective and unselective wet chemical etching produces a superior mesa-wall which has limited Zn-diffusion to the active layer. BH laser fabricated by MOVPE and the dry-etching technique is also confirmed as having high-reliability in practical usage.     

High speed and low loss, bulk electroabsorption waveguide modulators at 1.3 mu m

Bulk InGaAsP electroabsorption waveguide modulators based on a novel multiquaternary layer design which have a tapered-fiber-modulator-tapered-fiber insertion loss as low as 4.5 dB and a small-signal frequency response in excess of 11 GHz at lambda =1.33 mu m are described. This design allows one to decouple somewhat the electrical and optical properties of the device. By choosing the appropriate quaternary composition of the core and the cladding layers, the coupling to a tapered fiber can be optimized, while the position and thickness of the p-i-n junction can be varied independently to meet operating voltage and speed requirements without affecting the waveguide mode. A -3 dB small-signal modulation bandwidth in excess of 11 GHz was measured.<>     

Optimisation of a-factor for quantum dot InAs/GaAs fabry-perot lasers emitting at 1.3 /spl mu/m

Dynamic measurements of the Henry factor alpha_H of InAs/GaAs Fabry-Perot lasers are compared for 3-, 5- and 10-QD layers. While alpha_H dramatically increases with the bias current for 3- and 5-QD stacks, it only amounts to <4 for the 10-layer stack at high currents, a value similar to that of QW-lasers     

High-speed 1.3 μm GaInAs detectors fabricated on GaAs substrates

High-speed interdigitated metal-semiconductor-metal detectors have been fabricated on non-lattice-matched, semi-insulating, GaAs substrates using two GaInAs layers of differing indium concentrations to accommodate most of the lattice mismatch by interface misfit dislocations. Bandwidths as high as 3 GHz were measured with none of the detrimental low-frequency gain usually observed in this type of device. This is attributed to the inhibition of the surface trapping of photoinduced carriers by a graded pseudomorphic layer at the surface     

Silicon Mach-Zehnder waveguide interferometers operating at 1.3 mu m

Mach-Zehnder waveguide interferometers have been fabricated in silicon and operation has been demonstrated at lambda =1.3 mu m. The switching mechanism is based on the thermally induced variation of the refractive index of crystalline silicon. Modulation depths of 40% were obtained for switching powers of 30 mW and switching times of 50 mu s.<>     

High-power (200 mW) singlemode operation of InGaAsN/GaAs ridge waveguide lasers with wavelength around 1.3 /spl mu/m

High-power narrow ridge waveguide lasers emitting with a wavelength around 1.3 /spl mu/m were realised with a single In/sub 0.36/GaAsN/sub 0.022/ quantum well with GaAs barriers. A narrow vertical far-field angle of 35/spl deg/ was obtained. Single lateral mode continuous-wave operation with slope efficiency of 0.57 W/A, series resistance of 2.6 /spl Omega/, and kink-free output power of 210 mW was achieved.     

Low-threshold CW GaInNAsSb/GaAs laser at 1.49 /spl mu/m

Low-threshold room temperature continuous wave 1.49 /spl mu/m GaInNAsSb lasers are presented. Room temperature threshold current density of 1.1 kA/cm/sup 2/ was observed with a high external quantum efficiency of 40% and maximum output power of 30 mW from both facets.     

High performance quantum dot lasers on GaAs substrates operating in 1.5 /spl mu/m range

Stacked InAs/InGaAs quantum dots are used as an active media of metamorphic InGaAs-InGaAlAs lasers grown on GaAs substrates by molecular beam epitaxy. High quantum efficiency (/spl eta//sub i/>60%) and low internal losses (/spl alpha/<3-4 cm/sup -1/) are realised. The transparency current density per single QD layer is estimated as /spl sim/70 A/cm/sup 2/ and the characteristic temperature is 60 K (20-85/spl deg/C). The emission wavelength exceeds 1.51 /spl mu/m at temperatures above 60/spl deg/C.     

MOVPE-grown GaInNAs VCSELs at 1.3 /spl mu/m with conventional mirror design approach

1.3 /spl mu/m oxide confined GaInNAs VCSELs designed using the same design philosophy used for standard 850 nm VCSELs is presented. The VCSELs have doped mirrors, with graded and highly doped interfaces, and are fabricated using production-friendly procedures. Multimode VCSELs (11 /spl mu/m oxide aperture) with an emission wavelength of 1287 nm have a threshold current of 3 mA and produce 1 mW of output power at 20/spl deg/C. The maximum operating temperature is 95/spl deg/C. Emission at 1303 nm with 1 mW of output power and a threshold current of 7 mA has been observed from VCSELs with a larger detuning between the gain peak and the cavity resonance.     

Low-Loss Two-Dimensional GaAs Epitaxial Waveguides at 10.6-/spl mu/m Wavelength

The successful fabrication of low-loss two-dimensional GaAs epitaxial waveguides by chemical etching for use in integrated optics at 10.6 /spl mu/m is reported. Selective excitation of specific E/sub pq//sup y/ modes was observed by placing the prism at specific angles in the horizontal plane. Loss measurements showed no increase in attenuationfor lower order E/sub pq//sup y/ modes (as compared to corresponding one-dimensional waveguide modes) when the guide width is 50 /spl mu/m. As the guide width is reduced, there is a significant increase in attenuation as p increases.     

Room-temperature continuous-wave 1.55 /spl mu/m GaInNAsSb laser on GaAs

The first low-threshold 1.55 /spl mu/m lasers grown on GaAs are reported. Lasing at 1.55 /spl mu/m was observed from a 20/spl times/2400 /spl mu/m as-cleaved device with a room-temperature continuous-wave threshold current density of 579 A/cm/sup 2/, external efficiency of 41%, and 130 mW peak output power. The pulsed threshold current density was 550 A/cm/sup 2/ with >600 mW peak output power.     

Over 1.3 /spl mu/m CW laser emission from InGaSb quantum-dot vertical-cavity surface-emitting laser on GaAs substrate

An Sb-based quantum-dot vertical-cavity surface-emitting laser (QD-VCSEL) operating in the 1.3 /spl mu/m optical communication waveband is presented. A QD-VCSEL containing high-density InGaSb QDs in the active region is fabricated on GaAs substrate. The density of InGaSb QDs is drastically increased using a new method of an Si atom irradiation technique. A long-wavelength laser emission at 1.34 /spl mu/m is successfully achieved on the InGaSb QD-VCSEL in CW operation at room temperature.     

High-performance 1.5 /spl mu/m GaInNAsSb lasers grown on GaAs

Substantially reduced threshold current density and improved efficiency in long-wavelength (>1.4 /spl mu/m) GaAs-based lasers are reported. A 20/spl times/1220 /spl mu/m as-cleaved device showed a room temperature continuous-wave threshold current density of 580 A/cm/sup 2/, external efficiency of 53%, and 200 mW peak output power at 1.5 /spl mu/m. The pulsed threshold current density was 450 A/cm/sup 2/ with 1145 mW peak output power.