A wavelength-tunable duplex integrated light source for fastwavelength switching

A new monolithically integrated opto-electronic device has been developed for fast wavelength switching in photonic packet switching. The integrated device, called a tunable duplex integrated light source comprises two distributed Bragg reflector lasers (DBR-LDs), two electroabsorption optical switches, a Y-shaped waveguide coupler, an electroabsorption modulator, and two thermal drift compensators (TDCs). The tuning range of the DBR-LDs is 3 nm, and the wavelength switching time of the optical switches is estimated to be 60 ps including a 50 ps rise time for the electrical pulse generator. The wavelength of a 10 Gb/s NRZ-modulated optical signal is switched without bit loss. Thermal crosstalk between the DBR-LDs, and wavelength drift of the DBR-LDs, which is due to a thermal transient, are effectively suppressed by thermal-drift-compensation operation using the TDCs     

Low-switching-voltage InGaAsP/InP waveguide interferometricmodulator for integrated optics

An InGaAsP/InP electrooptic Mach-Zehnder modulator consisting of two 3-dB Y-branch couplers and phase modulation arms is fabricated by the metal-organic vapor-phase epitaxy growth method. A schematic illustration and cross section of the interferometric modulator as well as the current-voltage characteristics of the arms are shown. The modulator is formed by a waveguide having almost the same cross-sectional configuration as a double-heterostructure laser diode. The switching voltage of 4.5 V applied to one arm of the modulator results in an excitation of about 7 dB     

Electric-field-sensitive polymers: Reversible bending of rod-shaped polymer gels in salt solutions

Neutral gel (acrylamide [AAm] gel) and anionic gel (copolymer gel of 2-acrylamido-2-methyl-1-propane sulfonic acid [AMPSA] and butyl methacrylate [BMA]) were prepared to observe the bending phenomena in various salt solutions. The bending pattern of AAm gel was closely related to salts used in the aqueous media. The competition NMR technique was used to understand the interaction of salts with the polymer matrix. In the case of copolymer gel, the bending pattern did not show the salt dependence and the bending angle decreased after reaching a maximum. © 1994 John Wiley & Sons, Inc.     

Optically triggered off-switching in a bistable laser diode using atwo-electrode DFB-LD

Optically triggered off-switching in a bistable laser diode (BLD) with inhomogeneous excitation is demonstrated for the first time. By injecting an optical pulse with a slightly different frequency from that of the BLD, the BLD is switched from the stable on to the stable off position. This off-switching results from beat vibration between the BLD lasing light and the externally injected light     

Tunable optical-wavelength conversion using anoptically-triggerable multielectrode distributed feedback laser diode

Tunable optical-wavelength conversion with tunability greater than 5 Å using a multielectrode distributed-feedback laser diode (DFB LD) with a saturable absorber is discussed. This device is not dependent on input polarization and can operate at up to 500 MHz. Preliminary results of an optical switching experiment using the tunable wavelength converter and optical narrowband filter with a DFB LD amplifier are also reported     

Propagation-mode-controlled fabrication of self-written waveguide in photosensitive polyimide for single-mode operation

We have developed a new fabrication method of single-mode self-written waveguide by controlling the propagation mode in an optical fiber. This method is very appropriate for repeatable fabrication of the single-mode self-written waveguide. Since a Gaussian-like near-field pattern is required for the fabrication of a tiny and uniform waveguide core, the propagation mode in a conventional optical communication fiber was controlled by coupling with an optical fiber having 3-/spl mu/m core, which shows a single-mode operation at visible wavelength region. Single-mode propagation at optical communication wavelength was confirmed for the fabricated self-written waveguide. The evaluated core diameter of the self-written waveguide was /spl sim/9.5 /spl mu/m.     

Structural characterization of GaAs<Subscript>1−x</Subscript>Bi<Subscript>x</Subscript> alloy by rutherford backscattering spectrometry combined with the channeling technique

Rutherford backscattering spectrometry (RBS) combined with the channeling technique has been applied to a GaAs_1−xBi_x epilayer to investigate concentration and lattice location of Bi atoms and crystalline quality of the epilayer. The metastable GaAs_1−xBi_x alloy layer was grown on a GaAs substrate at a temperature as low as 365°C. The GaBi mole fraction obtained was 2.6 ± 0.2%. Angular scans for [100] and [111] crystal directions reveal that the incorporated Bi atoms exactly occupy substitutional sites in the GaAs crystal lattice. Crystal perfection of the GaAs_1−xBi_x metastable alloy is fairly good in spite of the low growth temperature.     

Broad-range tunable wavelength conversion of high-bit-rate signalsusing super structure grating distributed Bragg reflector lasers

Tunable wavelength conversion of a 10 Gb/s signal over a broad wavelength range of about 90 nm is achieved by using a super structure grating distributed Bragg reflector laser. The extinction ratio dependence of converted signal light on input signal light power and bias current to the laser active region is discussed. The extinction ratio becomes large when the input signal light power increases and the bias current decreases. Bit error rate measurements show that error-free, penalty-free wavelength conversion is achieved when the extinction ratio is large (12.5 dB) and that the bit rate which error-free wavelength conversion is possible increases as the input signal light power increases. Twenty Gb/s signal wavelength conversion is also demonstrated