High-speed and low-drive-voltage monolithic multiple quantum-wellmodulator/DFB laser light source

Monolithic integration of an InGaAsP/InGaAs multiple quantum well (MQW) distributed-feedback (DFB) laser with a high-speed InGaAs/InAlAs MQW intensity modulator is demonstrated. A 3-dB bandwidth. in excess of 16 GHz and low-drive-voltage operation (4.0 V) for a 20-dB on-off ratio are obtained. Good coupling efficiency between an MQW DFB laser and an MQW modulator is accomplished using hybrid crystal growth of MO-VPE and MBE     

InGaAs/InGaAlAs MQW lasers with InGaAsP guiding layers grown by gas source molecular beam epitaxy

An InGaAs/InGaAlAs multiple-quantum-well (MQW) laser was grown by gas source molecular beam epitaxy (GS-MBE). The laser has InP cladding layers and InGaAsP guiding layers, and the active layer is composed of an InGaAs/InGaAlAs MQW layer. Electrons are injected into the MQW active layer by tunneling through the barriers. The threshold current of the InGaAs/InAlAs buried-heterostructure (BH)-MQW lasers was as low as 9.6 mA. The relaxation oscillation frequency of the InGaAs/InAlAs MQW lasers was found to be larger than that of the InGaAs/InGaAsP MQW lasers with the same structure.<>     

Long-wavelength waveguide multiple-quantum-well (MQW) optical modulator with 30:1 on/off ratio

Large on/off ratio optical modulation of long-wavelength light propagating along the plane of InGaAs/InAlAs multiple-quantum-well (MQW) structures grown by molecular beam epitaxy (MBE) is obtained for the first time. These waveguide MQW optical modulators have a modulation on/off ratio of 30:1 (15 dB) at a driving voltage as low as 9 V, and a capacitance-limited pulse response of 280 ps (FWHM). This measurement is the first step in achieving faster and higher extinction ratio devices.     

Long wavelength waveguide multiple quantum well optical modulators

The first measurements of large anisotropic modulation of long-wavelength light with a large on/off ratio and low driving voltage propagating along the plane of InGaAs/InAlAs multiple quantum well (MQW) structures grown by molecular beam epitaxy (MBE) are reported. Photocurrent response and optical modulation of waveguide pin diodes is measured for incident light polarization parallel and perpendicular to the MQW layers emitting from a color center laser. The incident-light power and wavelength dependence of on/off ratio are also determined.     

MOVPE growth of strained InGaAs/lnAIAs MQWs for a polarization-insensitive electroabsorption modulator

Metalorganic vapor phase epitaxial growth of a strained InGaAs/lnAIAs multiquantum well (MQW) structure was carried out for optical electroabsorption modulators. A high-quality MQW layer can be grown by introducing compressive strain into InAlAs barrier layers against tensile-strained well layers. We have also demonstrated strained InGaAs/lnAIAs MQW electroabsorption modulators with polarization insensitivity by using these layers and have obtained a highquality modulator with a low driving voltage of 1.7 V and a wide 3-dB bandwidth of over 20 GHz.     

Extremely large band gap shifts for MQW structures by selectiveepitaxy on SiO2 masked substrates

The authors investigate selective epitaxy through SiO₂ masks of varied geometry with the goal of making planar photonic integrated circuits. The InGaAs/InP, InGaAsP/InP, and InGaAs/InGaAsP MQW material systems are studied with atmospheric and 100-torr MOVPE. Extremely large bandgap shifts (136 meV) can be achieved, more than enough to allow construction of lasers, modulators, and low-loss waveguides in a single plane     

Monolithic integration of InGaAs/InP DFB lasers and InGaAs/InAlAs MQW optical modulators

The first successful monolithic integration of InGaAsP/InP distributed feedback (DFB) lasers and InGaAs/InAlAs multiple quantum well (MQW) optical modulators using LPE (liquid phase epitaxy)/MBE (modlecular beam epitaxy) hybrid growth reported. A 14% light output modulation is observed in this integrated device.     

High-temperature excitons and enhanced electroabsorption in InGaAs/InAlAs multiple quantum wells

Sharp heavy-hole and light-hole excitons are clearly observed for the first time in InGaAs/InAlAs multiple-quantum-well (MQW) structures at temperatures ranging from ?190°C to 70°C. The halfwidth of the heavy-hole exciton line is as narrow as 6.2 meV at room temperature. InGaAs/InAlAs MQWs are prepared in a PIN doped configuration by molecular beam epitaxy. An enhanced electroabsorption effect is also clearly observed in long-wavelength-region MQWs.     

Multiple quantum well PIN optoelectronic devices and a method of restoring failed device characteristics

Multiple quantum well (MQW) optical modulators have a wide range of applications in fiber-optic and remote communication systems. One of the challenges in producing reliable devices is maintaining the necessary PIN electrical characteristics while having large areas of complex MQW structures for optical processing. We report the first direct correlation between crystalline material imperfections and reverse bias behavior in MQW PIN devices. Molecular beam epitaxy grown GaAs/AlGaAs and strained InGaAs/AlGaAs MQW PIN structures are examined. Defects originating in the epitaxial material provide a conducting path along the PIN junction degrading the device performance and lowering the yield. Defectectomy, a method of eliminating the crystalline defects and restoring the device characteristics and improving the yield is described.     

Tapered waveguide InGaAs/InGaAsP multiple-quantum-well lasers

The use of ultrathin etch-stop techniques to expand the vertical optical mode size adiabatically in 1.5-μm InGaAs/InGaAsP MQW lasers using a tapered-core passive intracavity waveguide structure is discussed. 30% differential quantum efficiency out the tapered facet, far-field FWHM of ~12° and a butt-coupling efficiency into a cleaved fiber of -4.2 dB, with -1-dB alignment tolerances of ~±3 μm, were achieved     

Design of a 1.65-μm-band optical time-domain reflectometer

The design and performance of a 1.65-μm-band single-mode optical time-domain reflectometer (OTDR) with a laser diode source are described. The approach employs a high-power laser diode with a strained-layer InGaAs/InGaAsP multiple-quantum-well (MQW) structure which is grown by metalorganic vapor phase epitaxy (MOVPE), an InGaAs avalanche photodiode, and methods for reducing the optical wiring loss in an optical unit. A 1.65-μm-band OTDR is realized with a single-way dynamic range of 25 dB at a pulse width of 1.0 μs     

Anisotropic electroabsorption and optical modulation in InGaAs/InAlAs multiple quantum well structures

The first measurements to be made of large anistropic electroabsorption and modulation of long-wavelength light propagating along the plane of InGaAs/InAlAs multiple quantum well (MQW) structures grown by molecular beam epitaxy (MBE) are reported. Photocurrent response of waveguide p-i-n diodes is studied for incident light polarization parallel and perpendicular to the MQW layers. Photocurrent increase with reverse bias throughout the entire photoresponse spectrum is observed for both polarizations. The MQW p-in optical modulator shows a capacitance-limited pulse response of 250 ps and the modulation depth is 14 percent.     

An InP/InGaAs p-i-n/HBT monolithic transimpedance photoreceiver

A monolithically integrated 1-Gb/s p-i-n/HBT transimpedance photoreceiver is discussed. The optoelectronic integrated circuit (OEIC) was made from metalorganic vapor-phase epitaxy (MOVPE)-grown InP/InGaAs heterostructures and had a transimpedance of 1375 Ω, a sensitivity of -26.1 dBm, >25-dB dynamic range, and a 500-MHz bandwidth     

InGaAs/InGaAsP MQW optical amplifier integrated withgrating-assisted vertical-coupler noise filter

A photonic integrated circuit with an InGaAs/InGaAsP multiple-quantum-well (MQW) traveling-wave optical amplifier and a grating-assisted vertical-coupler filter as a noise filter have been demonstrated. A fiber-to-amplifier/filter gain of ~0.5 dB and a 3-dB filter bandwidth (FWHM) of ~70 Å at 1.56 μm filter center wavelength have been achieved. This photonic circuit is potentially suitable as a building-block for preamplifier lightwave receivers or high-gain, high-power optical amplifiers which are essential for optical communication systems and lightwave networks     

X-band power AlGaAsInGaAs P-n-p HBTs

AlGaAs/InGaAs P-n-p heterojunction bipolar transistors (HBTs) were fabricated using carbon-doped material grown by nonarsine metal-organic vapor-phase epitaxy (MOVPE). F_max of 39 GHz and f_t of 18 GHz were obtained. Operated in common-base mode, a P-n-p HBT achieved 0.5-W output power with 8-dB gain at 10 GHz; saturated output power was 0.69 W. Results are presented for devices with emitter lengths from 120 to 600 μm     

Optically bistable operation in InGaAs/lnAIAs MOW laser diodes using resonant tunnelling effect

A new type of optically bistable operation using a resonant tunnelling effect has been achieved for InGaAs/lnAIAs MQW laser diodes for the first time. A clear optical bistability with a large on/off ratio was observed in the light output/voltage characteristics. Optical memory operation was also obtained with this MQW laser diode.     

The effects of laser irradiation on InGaAs/GaAs multiple quantum wells grown by metalorganic molecular beam epitaxy

We studied the effects of Ar ion laser irradiation during the growth of InGaAs/ GaAs multiple quantum wells (MQW) structures by metalorganic molecular beam epitaxy. Structural and optical properties were characterized by Nomarski microscopy, Dektak stylus profiler, and low-temperature photoluminescence (PL) measurements. For MQW structures grown at a relatively low substrate temperature (500°C), the laser irradiation influences greatly the growth process of the In^Ga^^As well and results in a large blue shift of about 2000à in the PL peak. Such a large blue shift suggests that laser modification during growth could have some novel applications in optoelectronics. On the other hand, the laser irradiation has relatively small effects on samples grown at a higher substrate temperature (550°C).     

Tensile-strained multiple quantum-well structures for a largerefractive index change caused by current injection

Tensile-strained multiple quantum-well (MQW) structures with camel-back shaped first valence sub-bands are proposed as structures with a large refractive index change caused by current injection. These structures have a high joint density of states at the absorption edge, and the injected carriers in the structures have a long lifetime because of separation in the k-space between electrons and holes. The refractive index change caused by current injection is calculated for camel-back InGaAs/InGaAsP strained MQW structures for 1.55 μm-wavelength light. These structures show a larger refractive index change than the other InGaAs/InGaAsP strained/unstrained MQW structures     

Effect of conduction-band discontinuity on lasing characteristicsof 1.5 μm InGaAs/In(Ga)AlAs MQW-FP lasers

The characteristic temperature (T₀), relaxation frequency (f_r), differential gain (dg /dn) and nonlinear gain coefficient (ϵ) of 1.5-μm InGaAs/In(Ga)AlAs multiple-quantum-well (MQW) Fabry-Perot (FP) lasers grown by gas source molecular beam epitaxy (GSMBE) are reported. It is found that T₀ is little affected by the difference in the conduction band discontinuity. A maximum T₀ value of 86 K is obtained. The dg/dn and ϵ∈ were calculated from the slope of the f_r versus √ power plot and the damping K-factor. It is demonstrated that dg/dn and ϵ of InGaAs/In(Ga)AlAs MQW lasers increase with an increase in the conduction band discontinuity     

Top-illuminated InGaAs/InP p-i-n photodiodes with a 3-dB bandwidthin excess of 26 GHz

Top-illuminated InGaAs p-i-n photodiodes have been fabricated from metal organic vapor-phase epitaxy (MOVPE) material, grown on semi-insulating InP substrates. A flat frequency response to 26 GHz has been measured, which is the highest figure yet reported for such devices. The predicted 3-dB bandwidth of these devices is 35 GHz