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We demonstrate dynamic parametric optical dispersion compensation in dynamic optical path networks (DOPNs). A fully automatic parametric tunable dispersion compensator (P-TDC) based on four-wave mixing process is developed with a fast tunable distributed amplification chirped sampled grating distributed reflector laser, a field-programmable gate array (FPGA) pump controller, and a fast dispersion monitor based on spectral shearing interferometer. The dispersion monitor detects a change in the dispersion of a path, and the monitoring signal is fed forward to the FPGA controller. The fast tunable laser sets its wavelength accordingly for the dispersion compensation through parametric process. A response time of <17 ms is demonstrated in a testbed of DOPN. The autonomous P-TDC has a potential response of submillisecond. [ABSTRACT FROM PUBLISHER]

We propose an operating principle for an optical nonvolatile switch utilizing surface plasmon antenna resonance controlled by giant magnetoresistance. The optical spectra of an array of nanoscale dipole antennas composed of Co/Cu multilayers with parallel and anti-parallel magnetization alignments were estimated by a first-principle calculation and a finite difference time domain electromagnetic field analysis. The extinction efficiency changed more than 40% in the infrared region due to the magnetization alignment, demonstrating its promise as a nonvolatile optical switch. [ABSTRACT FROM AUTHOR]

We develop a highly efficient quasi-phase-matched adhered ridge waveguide (QPM-ARW) in LiNbO _3 as a nonlinear material, and demonstrate tunable wavelength conversion without spectral inversion (SI) and parametric tunable dispersion compensation for a single-mode fiber (SMF) link. The QPM-ARW module with a second harmonic generation efficiency of 700 %/W achieves tunable wavelength conversion with a wavelength-tuning range of at least 25 nm through cascaded sum- and difference-frequency generation (SFG-DFG) process in which the signal and pumps are located symmetrically around the phase matching wavelength. The power penalty of the wavelength conversion is less than 0.6 dB for 43-Gb/s nonreturn-to-zero on–off-keying (NRZ-OOK) signals. We then apply the tunable wavelength conversion without SI to the parametric tunable dispersion compensation scheme, and achieve successful optical tunable dispersion compensation in 43-Gb/s NRZ-OOK transmissions over 53.2-km SMF. [ABSTRACT FROM PUBLISHER]

Studies the nonlinear gain dynamics in semiconductor quantum-dot (QD) optical amplifiers and their application to optical communication devices. Evaluation of optical nonlinearity in QD using four-wave-mixing methods and nonlinear pulse transmission measurements; Spontaneous emission spectra of QD optical amplifier.

Presents information on a study which discussed the third-order optical nonlinear susceptibilities... in compressively strained and nonstrained Indium Gallium Arsenic (InGaAs)-InGaAsPhosporus quantum wells (QW) under the population inversion condition. Optical nonlinear effects in the QW under the population inversion condition; Effect of strain on... in QW; Conclusion.

The ultrafast electron dynamics accompanying intersubband excitation in an InGaAs/AlAs/AlAsSb double quantum well has been investigated by femtosecond pump-probe spectroscopy. The photoinduced changes in the refractive index that causes cross-phase modulation is dominated by a decreased number as well as increased temperature of the electrons in the lower conduction subbands. The change in the number of conduction electrons decays monotonically, whereas the change in the electron temperature exhibits a maximum at around 0.9 ps after the photoexcitation. Heating of the conduction electrons is caused by their excess energy after intersubband longitudinal-optical phonon scattering. [ABSTRACT FROM AUTHOR]

Targeting future LAN applications, we demonstrate optical time domain multiplexing operation at 172-Gb/s using integratable semiconductor devices, i.e., intersubband transition all-optical gates, very short reach modules, semiconductor optical amplifiers, and mode-locked laser diodes. Bit-error rate (<\10^-6) well below the forward error correction limit was achieved successfully. [ABSTRACT FROM PUBLISHER]

We have experimentally investigated the effects of dispersion on subpicosecond pulse propagation over two-dimensional (2D) photonic-crystal-slab line-defect waveguides by time domain measurements. Using a heterodyne detection technique, pulse shapes after propagating along the waveguide were recorded as cross-correlated traces. When the pulse central frequency approached the band edge of the guided mode, the pulses were temporally delayed and their shapes were found to be broadened asymmetrically; this effect originated from the group velocity dispersion (GVD), encompassing higher-order dispersion effects. Theoretical pulse shapes, including third-order dispersion (TOD), agreed well with the experimental results. When the group velocity (vg) reached 0.08c, c being the speed of light, we found a GVD of ∼5.0 ps2/mm and a TOD of ∼0.3 ps3/mm. Experimentally obtained vg, GVD, and TOD characteristics agreed well with those obtained from 2D plane-wave-expansion band calculations. [ABSTRACT FROM AUTHOR]

The nonlinear optical effects in frequency-modulation mode-locked semiconductor laser diodes have been examined. The numerical simulation carried out in the frequency domain showed that the asymmetric nonlinear optical gain, which causes mode instability in mode-locked lasers, can be compensated for by an additional phase modulator. The stabilization of multimode oscillation was experimentally confirmed by applying phase modulation to the grating coupled laser diode. [ABSTRACT FROM AUTHOR]

We report the growth of BeZnCdSe quantum-well laser diode (LD) structures with a short-period superlattice cladding layer and demonstrate continuous-wave lasing in the pure-green spectral region (545 nm) at room temperature. The threshold current density and voltage of a 5-µm-wide gain-guided laser were found to be 1.7 kA/cm2 and 10.4 V, respectively. This threshold current density is sufficiently low compared with that of InGaN/GaN green LDs. [ABSTRACT FROM AUTHOR]

Wavelength conversion using nondegenerate four-wave mixing in quantum-dot optical amplifiers is investigated. From the detuning frequency dependence of χ[sup (3)], derived from the conversion efficiency, we consider that, within the range of detuning in the experiment, spectral-hole burning and carrier heating are responsible, and that their time constants, i.e., carrier relaxation time to the ground state and the phonon scattering time, are in the range of 60-140 and 200-400 fs, respectively. This indicates that the carrier supply to the ground level via relaxation from the higher levels is very fast and that a broad conversion bandwidth comparable to that of quantum-well devices is ensured. © 2000 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Abstract: In this study, we developed InGaAs/AlAs/InAlAs-based coupled double quantum wells (CDQWs). The CDQW design was intended to obtain a high conduction band offset and to decrease the residual strain of the CDQWs. The design enabled the CDQWs to exhibit a clear 1550nm peak of optical absorption due to the intersubband transition, and a structure in which the CDQWS were stacked 60 times was obtained. However, the optical absorption wavelength of the interband transition was slightly short for obtaining high cross phase modulation efficiency. [Copyright &y& Elsevier]

Abstract: We have investigated the MOVPE growth of InAs1− x Sb x quantum dots (QDs) on vicinal InP(001) substrate for DFB laser applications. Miscut orientation was adopted toward the [11¯0] direction in which InAsSb quantum wires elongate on normal InP(001) substrate. The interval between the QDs and the lateral size of the QDs in the [110] direction decreased as the Sb fraction was increased, which brought the density to as high as 1.1×1011 cm−2 of InAsSb QDs. The InAsSb QDs were stacked with 30-nm-thick InGaAsP spacer layers for 10 periods without correlation, and had an emission of a wavelength at around 1.55μm although the segregation of Sb atoms was slightly observed. A pn-buried-heterostructure-type DFB laser with InAsSb-QD active layer was fabricated. The lasing wavelength was 1540.6nm at 25°C, and CW, single-mode lasing operation was demonstrated up to 100°C. [Copyright &y& Elsevier]

Abstract: We have investigated the effects of changing Sb fractions and misorienting InP(001) substrates on InAs1− x Sb x quantum structures grown by metal-organic vapor-phase epitaxy (MOVPE), with the aim of obtaining small quantum dots (QDs) with 1.55-μm emission. At medium Sb content, InAsSb tended to form quantum wires (QWRs) with widths of less than 20nm along the direction on InP(001), which was due to the surfactant effect. The size of these narrow InAsSb QWRs decreased as the miscut angles toward the direction of the vicinal InP(001) substrates was increased, and the InAsSb shapes changed from QWRs into QDs. Nearly 1.55-μm-emitting InAs0.61Sb0.39 QDs with lateral sizes of 20–30nm embedded in InGaAsP barriers were fabricated on a vicinal substrate with a miscut of 5°, which will enable InP-based QD-telecom device applications. [Copyright &y& Elsevier]

Abstract: InAs1− x Sb x quantum structures grown on InP(001) by metalorganic vapor-phase epitaxy were investigated for a wide range of Sb content. InAs quantum dots (QDs) had an asymmetric shape elongated in the direction. Inducing small Sb content (x=0.06) reduced the size of QDs to around 30nm with improved shape symmetry, revealing that the migration length of adatoms or incorporation probability at steps was reduced by Sb. As the Sb content increased further, the shape changed into quantum wires (QWRs) (x=0.12, 0.39) with widths of 18–19nm, and quantum wells (x=0.70), which are related to the Sb surfactant effect. These results indicate that Sb has two competing functions in forming InAs1− x Sb x quantum structures: the surfactant effect and the modification of kinetics of adatoms or energetics at steps. The Sb amount is a key factor in controlling the shape of those structures. [Copyright &y& Elsevier]

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.