NUMERICAL ANALYSIS OF A NOVEL 980nm MICROCAVITY SEMICONDUCTOR OPTICAL AMPLIFIER WITH HIGH GAIN AND LOW NOISE

A novel microcavity semiconductor optical amplifier ( MCSOA) was proposed by incorporating top and bottom distributed Bragg reflectors ( DBRs) into the waveguide structure of conventional traveling-wave semiconductor optical amplifiers(TW-SOAs). The incoming( outgoing) light beam incidented onto (escaped from) the waveguide structure at a oblique angle through two optical windows, where the top DBR was etched away, and anti-reflection coating was deposited. The light beams inside the optical cavity were reflected repeatedly between two DBRs and propagated along waveguide in a zigzag optical path. The performance of the MCSOA was systematically investigated by extensive numerical simulation based on a traveling-wave model by taking into account the comprehensive effects of DBRs on both the amplification of signals and the filtering of spontaneous emission( SE). Our results show that the MCSOA is capable of achieving a fiber-to-fiber gain as high as 40dB and a low noise figure is less than 3.5dB.

40-Gb/s Low Chirp Electroabsorption Modulator Integrated With DFB Laser

A 40-Gb/s monolithically integrated transmitter containing an InGaAsP multiple-quantum-well electroabsorption modulator (EAM) with lumped electrode and a distributed-feedback semiconductor laser is demonstrated. Superior characteristics are exhibited for the device, such as low threshold current of 20 mA, over 40-dB sidemode suppression ratio at 1550 nm, and more than 30-dB dc extinction ratio when coupled into a single-mode fiber. By adopting a deep ridge waveguide and planar electrode structures combined with buried benzocyclobutene, the capacitance of the EAM is reduced to 0.18 pF and the small-signal modulation bandwidth exceeds 33 GHz. Negative chirp operation is also realized when the bias voltage is beyond 1.6 V.

Low-temperature magnetotransport behaviors of heavily Mn-doped (Ga,Mn)As films with high ferromagnetic transition temperature

We report the low-temperature magnetotransport behaviors of (Ga,Mn)As films with the nominal Mn concentration x larger than 10%. The ferromagnetic transition temperature T-C can be enhanced to 191 K after postgrowth annealing (Ga,Mn)As with x=20%. The temperature T-m, corresponding to the resistivity minimum in the curve of resistivity versus temperature at temperature below T-C, depends on Mn concentration, annealing condition, and magnetic field. Moreover, we find that the variable-range hopping may be the main conductive mechanism when temperature is lower than T-m.

Symmetry and optical transition rule for low-dimensional semiconductor system with spin-orbit interaction and magnetic field

Starting from effective mass Hamiltonian, we systematically investigate the symmetry of low-dimensional structures with spin-orbit interaction and transverse magnetic field. The position-dependent potentials are assumed to be space symmetric, which is ever-present in theory and experiment research. By group theory, we analyze degeneracy in different cases. Spin-orbit interaction makes the transition between Zeeman sub-levels possible, which is originally forbidden within dipole approximation. However, a transition rule given in this paper for the first time shows that the transition between some levels is forbidden for space symmetric potentials. (C) 2009 Elsevier Ltd. All rights reserved.

A Bragg-mirror-based semiconductor saturable absorption mirror at 800 nm with low temperature and surface state hybrid absorber

We present a novel 800-nm Bragg-mirror-based semiconductor saturable absorption mirror with low temperature and surface state hybrid absorber, with which we can realize the passive soliton mode locking of a Ti:sapphire laser pumped by 532-nm green laser which produces pulses as short as 37 fs. The reflection bandwidth of the mirror is 30 nm and the pulse frequency is 107 MHz. The average output power is 1.1 W at the pump power of 7.6 W.

Thermo-optic variable optical attenuator with low power consumption fabricated on silicon-on-insulator by anisotropic chemical etching

A thermo-optic Mach-Zehnder (MZ) variable optical attenuator based on silicon waveguides with a large cross section was designed and fabricated on silicon-on-insulator (SOI) wafer. Multimode interferometers were used as power splitters and combiners in the MZ structure. In order to achieve a smooth interface, anisotropic chemical etching of silicon was used to fabricate the waveguides. Isolating grooves were introduced to reduce power consumption and device length. The device has a low power consumption of 210 mW and a response time of 50 mus. (C) 2004 Society of Photo-Optical Instrumentation Engineers.

FexSi grown with mass-analyzed low-energy dual ion beam deposition

Heavily iron-implanted silicon was prepared by mass-analyzed low-energy dual ion beam deposition technique. Auger electron spectroscopy depth profiles indicate that iron ions are shallowly implanted into the single-crystal silicon substrate and formed 35 nm thick FexSi films. X-ray diffraction measurements show that as-implanted sample is amorphous and the structure of crystal is partially restored after as-implanted sample was annealed at 400degreesC. There are no new phases formed. Carrier concentration depth profile of annealed sample was measured by Electrochemical C-V method and indicated that FexSi film shows n-type conductivity while silicon substrate is p-type. The p-n junction is formed between FexSi film and silicon substrate showing rectifying effect. (C) 2003 Elsevier B.V. All rights reserved.

Low-threshold-current and high-out-power 660 nm laser diodes with a p-GaAs current blocking layer for DVD-RAM/R

We investigate a new structure of high-power 660-nm AlGaInP laser diodes. In the structure, a p-GaAs layer is grown on the ridge waveguide serving as the current-blocking layer, and nonabsorbing windows are only fabricated near the cavity facets to increase the catastrophic-optical-damage level. Stable fundamental mode operation was achieved at up to 80 mW without kinks, and the maximum output power was 184 mW at 22 degrees C. The threshold current was 40 mA.