949 resultados para dual-wavelength


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By using the mass-analyzed low energy dual ion beam deposition technique, a high quality epitaxial, insulating cerium dioxide thin film with a thickness of about 2000 Angstrom, has been grown on a silicon (111) substrate. The component species, cerium and oxygen, are homogeneous in depth, and have the correct stoichiometry for CeO2. X-ray double-crystal diffraction shows that the full width at half maximum of the (222) and (111) peaks of the film are less than 23 and 32 s, respectively, confirming that the film is a perfect single crystal. (C) 1995 American Institute of Physics.

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We numerically investigate four-wave-mixing (FWM) based multichannel wavelength conversion for amplitude-modulated signals, phase-modulated signals, together with mixed amplitude and phase modulated signals. This paper also discusses the influence of stimulated Brillouin scattering (SBS) effects on high-efficiency FWM-based wavelength conversion applications. Our simulation results show that DPSK signals are more suitable for FWM-based multichannel wavelength conversion because the OOK signals will suffer from the inevitable datapattern-dependent pump depletion. In future applications, when the modulation format is partially upgraded from OOK to DPSK, the influence of OOK signals on the updated DPSK signals must be considered when using multichannel wavelength conversion. This influence becomes severe with the increase of OOK channel number. It can be concluded that DPSK signals are more appropriate for both transmission and multichannel wavelength conversion,especially in long haul and high bit-rate system.

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This paper presents a wide tuning range CMOS frequency synthesizer for a dual-band GPS receiver,which has been fabricated in a standard 0.18μm RF CMOS process. With a high Q on-chip inductor, the wide-band VCO shows a tuning range from 2 to 3.6GHz to cover 2.45 and 3.14GHz in case of process corner or temperature variation,with a current consumption varying accordingly from 0.8 to 0.4mA,from a 1.8V supply voltage. Measurement results show that the whole frequency synthesizer consumes very low power of 5.6mW working at L1 band with in-band phase noise less than - 82dBc/Hz and out-of-band phase noise about - ll2dBc/Hz at 1MHz offset from a 3. 142GHz carrier. The performance of the frequency synthesizer meets the requirements of GPS applications very well.

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We propose a fiber-to-waveguide coupler for side-illuminated p-i-n photodiodes to obtain high responsivity and low polarization dependence that is grown on InP substrate and is suitable for surface hybrid integration in low cost modules. The fiber-to-waveguide coupler is based on a diluted waveguide,which is composed of ten periods of undoped 120nm InP/80nm InGaAsP (1.05μm bandgap) multiple layers. Using the semi-vectorial three dimensional beam propagation method (BPM) with the central difference scheme,the coupling efficiency of fiber-to-waveguide under different conditions is simulated and studied,and the optimized conditions for fiber-to-waveguide coupling are obtained. For TE-like and TM-like modes,the calculated maximum coupling efficiency is higher than 94% and 92% ,respectively. The calculated polarization dependence is less than 0. ldB,showing good polarization independence.

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A novel unselective regrowth buried heterostructure long-wavelength superluminescent diode (SLD) with a graded composition bulk InGaAs active region is developed by metalorganic vapor phase epitaxy (MOVPE). At a 150mA injection current, the full width at half maximum of the emission spectrum of the SLD is about 72nm, ranging from 1602 to 1674nm. The emission spectrum is smooth and flat. The ripple of the spectrum is less than 0.3dB at any wavelength from 1550 to 1700nm. An output power of 4.3mW is obtained at a 200mA injection current under continuous-wave operation at room temperature. This device is suitable for the applications of light sources for gas detectors and L-band optical fiber communications.

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Quantum dot gain spectra based on harmonic oscillator model are calculated including and excluding excitons. The effects of non-equilibrium distributions are considered at low temperatures. The variations of threshold current density in a wide temperature range are analyzed and the negative characteristic temperature and oscillatory characteristic temperature appearing in that temperature range are discussed. Also,the improvement of quantum dot lasers' performance is investigated through vertical stacking and p-type doping and the optimal dot density, which corresponds to minimal threshold current density,is calculated.

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We report a wavelength tunable electro-absorption modulated DBR laser based on a combined method of SAG and QWI. The threshold current is 37mA and the output power at 100mA gain current is 3.5mW. When coupled to a single-mode fiber with a coupling efficiency of 15% ,more than a 20dB extinction ratio is observed over the change of EAM bias from 0 to -2V. The 4.4nm continuous wavelength tuning range covers 6 channels on a 100GHz grid for WDM telecommunications.

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A semiconductor optical amplifier and electroabsorption modulator monolithically integrated with a spotsize converter input and output is fabricated by means of selective area growth,quantum well intermixing,and asymmetric twin waveguide technology. A 1550-1600nm lossless operation with a high DC extinction ratio of 25dB and more than 10GHz 3dB bandwidth are successfully achieved. The output beam divergence angles of the device in the horizontal and vertical directions are as small as 7.3°× 18.0°, respectively, resulting in a 3.0dB coupling loss with a cleaved single-mode optical fiber.

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A 1.60μm laser diode and electroabsorption modulator monolithically integrated with a novel dualwaveguide spot-size converter output for low-loss coupling to a cleaved single-mode optical fiber are demonstrated.The devices emit in a single transverse and quasi single longitudinal mode with an SMSR of 25.6dB. These devices exhibit a 3dB modulation bandwidth of 15. 0GHz, and modulator DC extinction ratios of 16.2dB. The output beam divergence angles of the spot-size converter in the horizontal and vertical directions are as small as 7. 3°× 18. 0°,respectively, resulting in a 3. 0dB coupling loss with a cleaved single-mode optical fiber.

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A novel distribute feedback (DFB) laser which gave two different wavelengths under two distinct work conditions was fabricated. The laser consists of two Bragg gratings with different periods corresponding to wavelength spacing of 20 nm in an identical active area. When driving current was injected into one of the different sections separately, two different wavelengths at 1542.4 and 1562.5 nm were realized. The side mode suppression ratio (SMSR) of 45 dB or more both for the two Bragg wavelengths were achieved. The fabricating process of the laser was just the same as that of traditional DFB laser diode. This device can be potentially used in coarse wavelength division multiplexer (CWDM) as a promising light source and the technology idea can be used to enlarge the transmission capacity in metro area network (MAN).

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The time-resolved photoluminescence and steady photoluminescence (TRPL and PL) spectra on self-assembled InAs/GaAs quantum dots (QDs) are investigated. By depositing GaAs/InAs short period superlattices (SLs), 1. 48 μtm emission is obtained at room temperature. Temperature dependent PL measurements show that the PL intensity of the emission is very steady. It decays only to half as the temperature increases from 15 K to room temperature, while at the same time, the intensity of the other emission decreases by a factor of 5 orders of magnitude. These two emissions are attributed to large-size QDs and short period superlattices (SLs), respectively. Large-size QDs are easier to capture and confine carriers,which benefits the lifetime of PL, and therefore makes the emission intensity insensitive to the temperature.

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Resonant cavity enhancement (RCE) typed optical detector and modulator which operating at wavelength band of 1.06 μm is reported. The peak quantum efficiency of detector is reasonably high as 50% without bias, and the photocurrent contrast ratio of modulator is 3.6 times at -3.5 V as compared to 0 V. The incident angle dependence of RCE device's photoelectric response is investigated carefully.

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Self-organized In_(0.5)Ga_(0.5)As/GaAs quantum island structure emitting at 1. 35 (im at room temperature has been successfully fabricated by molecular beam epitaxy (MBE) via cycled (InAs)_1/( GaAs)_1 monolayer deposition method. Photoluminescence (PL) measurement shows that very narrow PL linewidth of 19.2 meV at 300 K has been reached for the first time, indicating effective suppression of inhomogeneous broadening of optical emission from the In_(0.5)Ga_(0.5)As islands structure. Our results provide important information for optimizing the epitaxial structures of 1.3 μm wavelength quantum dot (QD) devices.

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The two-section tunable ridge waveguide distributed Bragg reflector (DBR) laser fabricated by the selective intermixing of an InGaAsP-InGaAsP quantum well structure is presented. The threshold current of the laser is 51mA. The tunable range of the laser is 4.6nm, and the side mode suppression ratio (SMSR) is 40dB.