Harmonic Millimeter Wave Generation and Frequency Up-Conversion Using Optical Injection Locking and Brillouin Selective Sideband Amplification

Harmonic millimeter wave (mm-wave) generation and frequency up-conversion are experimentally demonstrated using optical injection locking and Brillouin selective sideband amplification (BSSA) induced by stimulated Brillouin scattering in a 10-km single-mode fiber. By using this method, we successfully generate third-harmonic mm-wave at 27 GHz (f(LO) - 9 GHz) with single sideband (SSB) modulation and up-convert the 2GHz intermediate frequency signal into the mm-wave band with single mode modulation of the SSB modes. In addition, the mm-wave carrier obtains more than 23 dB power gain due to the BSSA. The transmission experiments show that the generated mm-wave and up-converted signals indicate strong immunity against the chromatic dispersion of the fibers.

Room-Temperature Continuous-Wave Operation of InGaN-Based Blue-Violet Laser Diodes with a Lifetime of 15.6 Hours

We report our recent progress of investigations on InGaN-based blue-violet laser diodes (LDs). The room-temperature (RT) cw operation lifetime of LDs has extended to longer than 15.6 h. The LD structure was grown on a c-plane free-standing (FS) GaN substrate by metal organic chemical vapor deposition (MOCVD). The typical threshold current and voltage of LD under RT cw operation are 78 mA and 6.8 V, respectively. The experimental analysis of degradation of LD performances suggests that after aging treatment, the increase of series resistance and threshold current can be mainly attributed to the deterioration of p-type ohmic contact and the decrease of internal quantum efficiency of multiple quantum well (MQW), respectively.

QUANTUM WAVE-GUIDE THEORY FOR MESOSCOPIC STRUCTURES

A one-dimensional quantum waveguide theory for mesoscopic structures is proposed, and the boundary conditions of the wave functions at an intersection are given. The Aharonov-Bohm effect is quantitatively discussed with use of this theory, and the reflection, transmission amplitudes, etc., are given as functions of the magnetic flux, the arm lengths, and the wave vector. It is found that the oscillating current consists of a significant component of the second harmonic. This theory is also applied to investigate quantum-interference devices. The results on the Aharonov-Bohm effect and the quantum-interference devices are found to be in agreement with previous theoretical results.

GAAS/GAALAS GRADED INDEX SEPARATE CONFINEMENT SINGLE QUANTUM-WELL SINGLE-MODE WAVE-GUIDE ELECTROABSORPTION LIGHT-MODULATOR

A GaAs/GaAlAs graded-index separate confinement single quantum well heterostructure single-mode ridge waveguide electroabsorption modulator was fabricated and investigated. For the modulator with a quantum well width of 100 angstrom and device length of 700-mu-m, an on/off ratio of 29.7 dB and estimated absorption insertion loss of 3 dB were obtained for TE polarised light with wavelength 8650 angstrom, and for TM polarisation the on/off ratio was 28.5 dB. With a switching voltage of 1 V, an on/off ratio of 15 dB was achieved. Photocurrent spectra exhibited a red shift of 600 angstrom of the absorption edge when the voltage applied to the PIN diode was varied from 0.5 to -7 V. The corresponding shift of the room temperature exciton peak energy was 96 meV.

Perpendicular-electric-field dependence of exciton binding energy studied by continuous-wave photoluminescence

The reduction of exciton binding energy induced by a perpendicular electric field in a stepped quantum well is studied. From continuous-wave photoluminescence spectra at 77 K we have observed an obvious blueshift of the exciton peak due to a spatially direct-to-indirect transition of excitons. A simple method is used to calculate the exciton binding energy while the inhomogeneous broadening is taken into account in a simple manner. The calculated result reproduces remarkably well the experimental observation.

TAILORED DFB LASER PROPERTIES BY INDIVIDUALLY CHIRPED GRATINGS USING BENT WAVE-GUIDES

DFB lasers with continuously and arbitrarily chirped gratings of ultrahigh spatial precision are implemented by a method we proposed recently, using bent waveguides on homogeneous grating fields. Choosing individual bending functions we generate special chirping functions and obtain additional degrees of freedom to tailor and improve specific device performances, We present two applications for lasers showing several improved device properties and the effectiveness of our method, First, we implement continuously distributed phase-shifted lasers, revealing a considerably reduced photon pile-up, higher single-longitudinal mode stability, higher output power, lower linewidth, and higher yield than conventional abruptly phase-shifted lasers, Second, a novel tuning principle is applied in chirped multiple-section DFB lasers, showing 5.5-nm wavelength tuning, without any gaps, maintaining high side-mode suppression.