We report a bandwidth variation technique in an acousto-optic filter. Utilizing the adiabatic conversion in both optical and acoustic modes, we obtain a novel hybrid waveguide composed of serial concatenation of single-mode fiber (SMF) and two-mode hollow optical fiber (HOF). On the basis of dissimilarity in the phase-matching conditions and beat-length dispersion in SMF and HOF, the FWHM of the resonant bands is varied from 3.8 to 190 nm near the 1.5-microm region in a single device. Furthermore, we theoretically analyze the acousto-optic coupling among the guided modes in HOF, which shows good agreement with experimental observations.

An unusual appearance of a peak in the deep-level transient spectroscopy (DLTS) data for minority-carrier traps from an InGaN∕GaN multiple-quantum-well (MQW) light-emitting diode, under a bias condition provided by a square pulse of varying height superimposed over the reverse-bias voltage, is newly observed and analyzed. The peak is attributed to hole traps, having the estimated activation energy of 0.7eV, in the last one (toward the p side) among the GaN barrier layers in the MQW structure. We have found that the ΔC∕Cr-versus temperature pattern from the DLTS measurement agrees well with the pattern predicted from the model of hole traps, i.e., the minority-carrier traps, in the MQW barrier layer, whose occupation probability is governed by the local hole quasi-Fermi level.

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Full-color synthesis was achieved, for what we believe is the first time, utilizing a novel 3x1 hard polymer-clad fiber coupler along with red, green, and blue (RGB) LED primaries. By using RGB LEDs that are coupled to three input ports, the device rendered full color from the output port with a circular emitting pixel of 135 microm in diameter with an extended color gamut. The proposed fiber-optic color synthesizer can provide a compact waveguide solution for the beam scanning display and the tunable pure white source for LED backlighting.