Gain-assisted surface plasmon polaritons (SPPs) propagation is realized by electrical pumping the InGaAsP quantum
wells (QWs) beneath the metal waveguide with asymmetric configuration. The long-range and short-range mode SPPs
are analyzed theoretically and observed experimentally under different levels of current injection. It is demonstrated that
among the complex SPP-coupled emission mechanisms, the short-range SPP is supported by stimulated amplification
(SA) in electrically-pumped QWs, and increases robustly to as 1.6 times of the long-range mode SPP in output power
over a travelling distance of 80μm. This stimulated SPP emission can be adopted for the minimization of the electrically
controlled optical modulator.
A new wavelength monitor based on a multimode interference waveguide is proposed for multiwavelength communication applications. The device characteristics are studied using the beam propagation method. By adjusting the waveguide's geometric length, different wavelength ranges can be addressed. Each device can monitor up to a 50-nm range and has accuracy <5 Å.
N-type strained GaInAsP/InP multiple quantum well (MQW) structures have been grown successfully using all solid source molecular beam epitaxy (MBE) and the effects of doping density in the wells on the quality of the MQW structures have been investigated. In the high-resolution x-ray diffraction curves, well-defined sharp satellite peaks up to the 15th order can be observed, indicating a very high crystalline quality of the MQW structures. With increase of Si-doping concentration in the wells, the lattice mismatch increases. The FWHM of the zero-order peak also increases and fits a Logistic function well with the doping density. The period of the MQW structures is found to decrease and the intensity of the first-order satellite peak to decays exponentially. All the observations can be explained by the changes in lattice constant, interface defects, dopant diffusion and possibly growth rate, caused by high doping in the wells of the MQW structures.
The two-color detection using the multiple quantum well infrared photodetector consisting of InGaAs/GaAs step quantum wells with AlGaAs/GaAs superlattice barriers is investigated. The bound-to-bound and bound-to-continuum transitions in the step quantum wells provide two responses with energy separation large enough for the dual-band detection in the mid- and long-wave infrared ranges. The photocurrent due to the bound-to-bound transition can be extracted with a low external electric field via the miniband in the superlattice barriers so that the high leakage current is avoided. The Stark's shifts caused by the coupling and separation of energy states were clearly observed and the relevant analysis is discussed. This work demonstrates the use of asymmetric quantum wells with superlattice barriers for the fabrication of multicolor infrared detectors.
Proc. SPIE. 4582, Optical Switching and Optical Interconnection
KEYWORDS: Quantum wells, Signal attenuation, Wavelength division multiplexing, Single mode fibers, Control systems, Micromirrors, Deep reactive ion etching, Optical switching, Variable optical attenuators, Optical interconnects
Variable optical attenuator (VOA) is undergoing to be a mainstream component of wavelength division multiplex (WDM) networks to monitor and control the optical power of wavelength channels. In this paper, a free-space VOA fabricated by micro electromechanical systems (MEMS) technology to operate in the 1.55 micrometers wavelength region is described. It employs a micromirror driven by an electrostatic comb drive to cut partially into the light beam between two single mode fibers (SMFs), enabling the attenuation. The micromirror has a size of 30 micrometers X 30 micrometers and is coated with aluminum to increase the reflectance. The moving fingers of comb drive and the micromirror are supported by folded suspension beams over the substrate. By applying different voltage to the comb drive, the micromirror translates to different position to achieve an attenuation ranging from 0.4dB to 50dB, and even higher. The nonlinear relationship between the position of the micromirror and attenuation is analyzed. The distributions of the light beams at the micromirror and the output fiber end are investigated respectively. And the influence of the separations between the micromirror, the input and output fiber ends is also discussed to obtain different attenuation resolutions. At low attenuation stages, fine tuning of attenuation is obtainable. The largest attenuation is driven by 21voltage. Deep reactive ion etching (DRIE) process is employed to fabricate the VOA and the micro loading effect is remedied by mask design.