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A study was conducted on the nondegenerate four-wave mixing properties of a long-cavity lambda/4-shifted distributed feedback laser with phase conjugate beams. The laser exhibited wide conversion range and high conversion efficiency. Results were used to calculate the third-order nonlinear characteristics of InP-InGaAs multiquantum wells. The single-device operation feature of the laser was found to be ideal for wavelength converters.

Four-wave mixing (FWM) in an InxGa1-xAs/AlAsySb1-y intersubband transition (ISBT) optical waveguide operating in the 1.55-μm wavelength region is discussed. The third-order optical nonlinear susceptibilities of InxGa1-xAs/AlAsySb1-y multiple quantum wells (MQWs) are estimated theoretically. ISBT excitation causes large third-order optical nonlinearity. χ(3) values of more than 1 × 1016 m2/V2 are obtained. The propagation of interacting waves for FWM in InxGa1-xAs/AlAsySb1-y ISBT optical waveguides is discussed. The interaction length is limited not only by phase matching but also by ISBT absorption. Sufficiently high FWM conversion efficiencies were obtained theoretically and experimentally for realizing coherent wavelength convertors. FWM in an InxGa1-xAs/AlAsySb1-y ISBT waveguide is a promising method for realizing compact and high-efficiency coherent wavelength conversion. [ABSTRACT FROM AUTHOR]

Presents a study which discussed the impact of ionization rates of holes in Al[subx]Ga[sub1-x]Sb near x=0.06, where resonance impact ionization is expected. Results of measurement of impact ionization rates; Impact ionization probability at the spin-split-off band; Scattering rates of holes.

The direct butt-joint coupling between the Si-wire-based Michelson interferometer (MI) and the InGaAs/AlAsSb quantum-well waveguide was performed to realize the hybrid integrated ultrafast intersubband transition switch. By attaining the narrow gap between the waveguides, we have observed the Michelson interference spectra between the two signal lights: one is the phase modulated light from the InGaAs/AlAsSb quantum-well waveguide and the other is the light returned from the Si loop mirror of MI. Furthermore, by controlling the phases and powers of two signal lights with the thermooptic phase shifter and variable coupler in MI, we have demonstrated the ultrafast all-optical gating operation with a response time of 2 ps. The all-optical gating switch with a small size of 0.3 mm 2.35 mm was successfully fabricated by the hybrid integration technologies of III-V and Si materials. [ABSTRACT FROM PUBLISHER]

We report on bistable operations in a microcavity formed on an AlGaAs-based photonic crystal slab at telecommunication wavelengths. We designed the cavity to achieve a high quality (Q)-factor, while maintaining a small mode volume; this was accomplished by removal of a single air hole. The fabricated microcavity exhibited a resonant peak with a Q-factor of 1900 at 1548 nm. In nonlinear transmission measurement, when the input power was increased, a bistable characteristic which was dependent on the detuned wavelength from the resonance was observed. The bistability was considered to originate from thermal nonlinearity due to two-photon absorption [ABSTRACT FROM PUBLISHER]

Conversion efficiency to longer wavelengths in four-wave-mixing-based wavelength conversion in optical semiconductor amplifiers is generally much lower than that in the opposite direction. This study demonstrates experimentally that this feature is drastically improved, and the asymmetry between conversion directions is eliminated by using quantum dots in the active layer. We attribute this to a reduction in linewidth enhancement factor due to the discreteness of the electron states in quantum dots. [ABSTRACT FROM PUBLISHER]

A nonlinear device capable of handling multiple wavelength channels simultaneously by using spectral-hole burning in the inhomogeneous broadening of the gain in self-assembled quantum dots is proposed. The multichannel property of this device stems from the localized absorption or gain change at the pump wavelength within the inhomogeneously broadened gain spectrum. The spectral width of the modulation and its time evolution was also evaluated. The result indicates the applicability of this device to multichannel operation. [ABSTRACT FROM PUBLISHER]

A wavelength converter that uses four-wave mixing (FWM) in an SOA-integrated distributed-feedback (DFB) laser was demonstrated. Lossless conversion up to 300-GHz detuning and a conversion efficiency of -5 dB at 1-THz detuning was achieved. The device exhibited low ASE (noise) level, and noise figure (NF) characteristics of 24 dB for 16-nm wavelength conversion was observed. This high-efficiency FWM wavelength conversion provided by a single device is promising for optical wavelength shifters in large-scale optical communication systems [ABSTRACT FROM PUBLISHER]

A surface-illuminated InP/GaInAs p-i-n photodiode with a planar, embedded structure has been fabricated. By minimizing the stray capacitance and by using semi-insulating substrates, the capacitance has been reduced to 0.08 pF for a diode with a diameter of 20 μm. It has been demonstrated that this photodiode has a very high-speed response of greater than 10 GHz. The present structure is suitable not only as a discrete p-i-n photodiode but also for optoelectronic integration. [ABSTRACT FROM AUTHOR]

We measured impact ionization rates in AlxGa1-xSb at x=0.06, where the band-gap energy Eg equals the spin-orbital splitting energy Δ, in an electric field of 1.5×105–3.2×105 V/cm. By considering exact field profile in the depletion layer for each sample, the ionization rates of AlxGa1-xSb have been determined to be α=2.35×106 exp(-1.30×106/E) and β=9.02×105 exp(-9.03×105/E). Although our data have not shown the resonant enhancement of hole ionization rates described by O. Hildebrand, W. Kuebart, and M. Pilkuhn [Appl. Phys. Lett. 37, 801 (1980)], exact values of impact ionization rates have been established in practical electric fields required for designing AlxGa1-xSb avalanche photodiodes. [ABSTRACT FROM AUTHOR]

Undoped GaSb crystals with mirror-like surfaces were obtained by liquid phase epitaxy from Sb-rich solutions. The background carrier concentration strongly depended on the growth temperature. By growing crystals below 600 °C, we can obtain a GaSb crystal with a background carrier concentration under 1016 cm-3. Photoluminescence studies showed that native defects related to Sb vacancies were significantly reduced in the GaSb crystal. [ABSTRACT FROM AUTHOR]

An Al0.053Ga0.947Sb avalanche photodiode (APD) has been fabricated and tested. First, measurement of an excess noise factor as well as an ionization rate ratio has been demonstrated. A low excess noise factor of 3.8, which is 1.2 dB lower than the conventional GaInAs APD, has been obtained. From this excess noise factor, the effective value of the hole-to-electron ionization rate ratio (keff) has been determined as high as 5, being in good agreement with the hole-to-electron ionization rate ratio (β/α) given by the multiplication data. This keff value is the highest ever reported for long-wavelength III-V APDs. [ABSTRACT FROM AUTHOR]

We demonstrate low-loss and broadband light transition from III-V functional layers to a Si platform via two-stage adiabatic-crossing coupler waveguides. A 900-µm-long and 2.7-µm-thick III-V film waveguide consisting of a GaInAsP core and InP cladding layers is transferred onto an air-cladding Si photonic chip by the µ-transfer printing (µ-TP) method. An average optical coupling loss per joint of 1.26 dB is obtained in C + L telecommunication bands (1530-1635 nm). The correlation between alignment offset and measured optical coupling loss is discussed with the frequency distribution of µ-TP samples. We also performed a photoluminescence measurement to investigate the material properties in the GaInAsP layer to see if they are distorted by the strong bending stress produced during the pick-up and print steps of the µ-TP process. The peak intensity reduction of 80-90% and a wavelength shift of 0-5 nm (blue shift) were observed after the process. The series of fundamental studies presented here, which combine multiple analyses, contribute to improving our understanding of III-V/Si photonic integration by µ-TP.

We demonstrate sub-millisecond tuning of a prototype parametric tunable dispersion compensator (P-TDC) based on cascaded polarization-diverse four-wave mixing (FWM) process with a fast tunable and highly wavelength-stable pump light source. The pump light source is developed using a tunable distributed amplification chirped sampled grating distributed reflector laser that is fully wavelength tunable by on-chip heaters with a 3-dB frequency response of 45 kHz, resulting in fast dispersion tuning of less than 50 μs without additional timing jitter. The P-TDC is developed as the first prototype to satisfy essential requirements for practical network uses: stable input-polarization diversity, input-wavelength preservation, and seamless dispersion tunability for entire C-band input wavelengths are simultaneously achieved.

n-channel body-tied partially depleted metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated for large current applications on a silicon-on-insulator wafer with photonics-oriented specifications. The MOSFET can drive an electrical current as large as 20 mA. We monolithically integrated this MOSFET with a 2 × 2 Mach-Zehnder interferometer optical switch having thermo-optic phase shifters. The static and dynamic performances of the integrated device are experimentally evaluated.

: We have studied the effects of shutter transients (STs) in molecular beam epitaxy (MBE). Two series of samples were grown by MBE and evaluated by X-ray diffraction (XRD) and X-ray reflectivity (XRR) measurements. The effects of STs were evaluated by growth rate (GR) analysis using a combination of growth time (GT) and thickness evaluated by XRD and XRR measurements. We revealed two opposite effects of STs: (1) overshoot of GR and (2) increase in GR with GT and subsequent saturation. Each effect was consistent with the previous studies; however, the previous studies showed no relationships between these two effects. By considering closing time of the shutter, the two opposite effects were well understood.