A Novel Two-Section Co-Cavity Wavelength Tunable Semiconductor Laser

于2010-11-23批量导入

Study on photoluminescence spectra of SiC

于2010-11-23批量导入

Growth and photoluminescence of InAlGaN films

Two quaternary InAlGaN films were grown by metal-organic chemical-vapor deposition (MOCVD) on sapphire (0001) substrates with and without high-temperature GaN interlayer, respectively. The structural and optical properties of the quaternary films were investigated by high-resolution X-ray diffraction (HRXRD), high-resolution electron microscopy (HREM), temperature-dependent photoluminescence (PL) spectroscopy and time-resolved photoluminescence (TRPL) spectroscopy. According to the HRXRD and PL results, it is demonstrated that two samples have the same crystal quality. The TRPL signals of both samples were fitted well as a stretched exponential decay from 14 K to 250 K, indicating significant disorder in the materials, which is attributed to recombination of excitons localized in disorder quantum nanostructures such as quantum dots or quantum disks originating from indium (In) clusters or In composition fluctuation. The cross-section HREM measurement further proves that there exist disorder quantum nanostructures in the quaternary. By investigating the temperature dependence of the dispersive exponent beta, it is shown that the stretched exponential decays of the two samples originate from different mechanisms. (C) 2003 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Fabrication of 1.3 mu m Si-based MEMS tunable optical filter

In this paper we report the fabrication of 1.3 mum Si-based MEMS tunable optical filter, by surface micromaching. Through wet etching of polyimide sacrificial layer, a tunable Fabry-Perot filter was successfully fabricated. We make the capacitance measurement of the prototype device, compare the experimental curve with the theoretical one, and explain the difference between them.

Photoluminescence characterization of 1.3 mu m In(Ga)As/GaAs islands grown by molecular beam epitaxy

1.3 mum wavelength In(Ga)As/GaAs nanometer scale islands grown by molecular beam epitaxy (MBE) were characterized by photoluminescence (PL) and atomic force microscopy (AFM) measurements. It is shown that inhomogeneous broadening of optical emission due to fluctuation of the In0.5Ga0.5As islands both in size and in compositions can be effectively suppressed by introducing a AlAs layer and a strain reduction In0.2Ga0.8As layer overgrown on top of the islands, 1.3mum emission wavelength with narrower line-width less than 20meV at room temperature was obtained.

Photoluminescence from carbon nanotubes

We observed yellow colored light emission bands from multiwalled carbon nanotubes in photo-luminescence (PL) experiments. The light emission band features indicate that the PL bands are associated with the electronic properties inherent to the carbon nanotube (CNT) structures.

Tunable MQW-DBR lasers using selective area growth

The tunable ridge waveguide distributed Bragg reflector (DBR) lasers designed for wavelength-division-multiplex (WDM) communication systems at 1.55 um by using selective area growth (SAG) is reported. The threshold current of the DBR laser is 62mA and the output power is more than 8mW. The isolation resistance between the active region and the Bragg region is 30K Ohm. The total tuning range is 6.5nm and this DBR laser can provide 6 continuous standard WDM channels with 100GHz channel spacing; in the tuning range, the single mode suppression ratio (SMSR) is maintained more than 32dB and the maximum output power variation is less than 3dB.

Photoluminescence characteristics of GaAs/AlGaAs quantum dot arrays fabricated by dry and dry-wet etching

GaAs/AlGaAs quantum dot arrays with different dot sizes made by different fabrication processes were studied in this work. In comparison with the reference quantum well, photoluminescence (PL) spectra from the samples at low temperature have demonstrated that PL peak positions shift to higher energy side due to quantization confinement effects and the blue-shift increases with decreasing dot size, PL linewidths are broadened and intensities are much reduced. It is also found that wet chemical etching after reactive ion etching can improve optical properties of the quantum dot arrays.

Wavelength tunable electroabsorption modulated DFB baser with thin film heater

　

The influence of oxygen content on photoluminescence from Er-doped SiOx

SiOx films with oxygen concentrations ranging 13-46 at.% were deposited by plasma enhanced chemical vapor deposition (PECVD) technique using: pure SiH4 and N2O mixture. Erbium was then implanted at an energy of 500 KeV with dose of 2x10(15) ions/cm(2). The samples were subsequently annealed in N-2 for 20 sec at temperatures of (300-950 degrees C). Room temperature (RT) photo-luminescence (PL) data were collected by Fourier Transform Infrared Spectroscopy (FTIS) with an argon laser at a wavelength of 514.5 nm and an output power from 5 to 2500 mw. The intense room-temperature luminescence was observed around 1.54 mu m. The luminescence intensity increases by 2 orders of magnitude as compared with that of Er-doped Czochralski (CZ) Si. We found that the Er3+ luminescence depends strongly on the SiOx microstructure. Our experiment also showed that the silicon grain radius decreased with increasing oxygen content and finally formed micro-crystalline silicon or nano-crystalline silicon. As a result, these silicon small particles could facilitate the energy transfer to Er3+ and thus enhanced the photoluminescence intensity.

Effect of carrier relaxation and emission on photoluminescence of InAs quantum dots

　

Preparation and photoluminescence of nc-Si/SiO2 MQW

The deposition rate and refractive index for a-Si(amorphous silicon) and SiO2 grown by PECVD were studied under different pressure, power and proportion of reactant source gases. a-Si/SiO2 MQW(multi-quantum well) with high quality was deposited under suitable conditions, in which the thickness of the a-Si layers is several nanometers. The sample of a-Si/SiO2 MQW was crystallized by laser annealing. Because of the confinement of the SiO2 layers, crystalline grains were formed during the a-Si layers were being crystallized. The size of the crystalline grains were not more than the thickness of the a-Si layers. The a-Si layers were crystallized to be nanometer crystalline silicon(nc-Si), therefore, nc-Si/SiO2 MQW was formed. For the a-Si/SiO2 MQW with 4.0nm a-Si wells separated by 5nm SiO2 barries, most of the a-Si were crystallized to silicon grains after laser annealing,and the size of the grains is 3.8nm. Strong photoluminescence with three peaks from the nc-Si/SiO2 MQW was detected at 10K. The wavelength of the peaks were 810nm, 825nm and 845nm, respectively.

Electroluminescence and photoluminescence of Si/SiGe self-assembly quantum dot structures

Comparative electroluminescence (EL) and photoluminescence (PL) measurements were performed on Si/Si0.6Ge0.4 self-assembly quantum dots (QDs) structures. The samples were grown pseudomorphically by molecular beam epitaxy, and PIN diodes for electroluminescence were fabricated. Assisted TEM pictures shows the SiGe self-assembly QDs are platelike. And it showed that the diameters of QDs are in range from 40nm to 140nm with the most in 120nm. Both EL and PL has a wide luminescence peak due to wide distribution of QDs dimensions. At low temperature (T=14K), EL peak has a red shift compared to the corresponding PL peak. Its full-width at half-maximum (FWHM) is about 97meV, a little smaller than that of corresponding PL peak. The reasons of position and FWHM changes of EL peak from QDs have been discussed.

Photoluminescence measurements on erbium-doped silicon

Erbium-implanted silicones were treated by lamp-heating rapid thermal annealing (RTA). Two types of erbium-related photoluminescence spectra appear under different anneal temperatures. 750 degrees C annealing optimizes the luminescence intensity, which does not change with anneal time. Exciton-mediated energy transfer model in erbium-doped silicon was presented. The emission intensity is related to optical active erbium concentration, lifetime of excited Er3+ ion and spontaneous emission time. The thermal quenching of the erbium luminescence in Si is caused by thermal ionization of erbium-bound exciton complex and nonradiative energy backtransfer processes, which correspond to the activation energy of 6.6 meV and 47.4 meV respectively.