2005, 3(8) Column
Chinese Optics Letters 第3卷 第8期
Coherent population transfer with chirped few-cycle laser pulses in an excited-doublet four-level systemDownload:572次
The behavior of population transfer in an excited-doublet four-level system driven by linear polarized few-cycle ultrashort laser pulses is investigated numerically. It is shown that almost complete population transfer can be achieved even when the adiabatic criterion is not fulfilled. Moreover, the robustness of this scheme in terms of the Rabi frequencies and chirp rates of the pulses is explored.
020.1670 coherent optical effects 190.7110 ultrafast nonlinear optics 320.1590 chirping Total cross sections (TCSs) of electrons scattering from triatomic molecules over the energy range from 30 to 5000 eV are investigated employing a new semi-empirical formula. The TCSs of electrons scattering from triatomic molecules SO2, NO2, and CO2 are calculated. The quantitative TCSs are in good agreement with those obtained by experiments. It is shown that the results derived from the semi-empirical formula are much closer to the measurements than other calculations.
020.2070 effects of collisions 020.0020 atomic and molecular physics 8*10-Gb/s transmission system over 1500 km on G.652 fiber dispersion compensated by chirped fiber gratingsDownload:781次
A low cost 8*10-Gb/s transmission system over 1500 km on conventional fiber using chirped fiber Bragg grating (CFBG) as dispersion compensator is demonstrated. The bit error rate (BER) below 10^(-10) at 1500 km is obtained. The channel spacing is 0.8 nm and the optical amplifier spacing is 100 km. Only 16 erbium-doped fiber amplifiers (EDFAs) are used.
060.0060 fiber optics and optical communications 060.2330 fiber optics communications 230.0230 optical devices 230.1480 Bragg reflectors We propose a 1st and 2nd order polarization mode dispersion emulator (PMDE) with one variable differential group delay (DGD) element using birefringence crystals and four polarization controllers (PCs). Monte Carlo simulations demonstrate that the output 1st and 2nd order polarization mode dispersion (PMD) generated by the PMDE consists with statistic theory. Compared with former PMDEs, this design is tunable, lower-cost, and more integrated for fabrication, which shows response time of 150 μs, response frequency of 3.8 kHz, working wavelength of 1550 nm, total power consumption of less than 3 W, working range of 0---84 ps and 0---3600 ps2 for 1st and 2nd order PMD emulation, respectively. Also, it is programmable and can be controlled by either singlechip or computer. It can be applied to study the outage probability of optical communication systems due to PMD effect and the effectiveness of PMD compensation.
060.2330 fiber optics communications 060.2420 fibers polarization-maintaining Natural color appearance is the key problem of color night vision field. In this paper, the color mood of daytime color image is transferred to the monochromic night vision image. This method gives the night image a natural color appearance. For each pixel in the night vision image, the best matching pixel in the color image is found based on texture similarity measure. Entropy, energy, contrast, homogeneity, and correlation features based on co-occurrence matrix are combined as texture similarity measure to find the corresponding pixels between the two images. We use a genetic algorithm (GA) to find the optimistic weighting factors assigned to the five different features. GA is also employed in searching the matching pixels to make the color transfer algorithm faster. When the best matching pixel in the color image is found, the chromaticity values are transferred to the corresponding pixel of the night vision image. The experiment results demonstrate the efficiency of this natural color transfer technique.
100.0100 image processing 040.3060 infrared 040.3780 low light level 100.2980 image enhancement Image expansion plays a very important role in image analysis. Common methods of image expansion, such as the zero-order hold method, may generate a visual mosaic to the expanded image, linear and cubic spline interpolation may blur the image data at peripheral regions. Since infrared images have the characteristics of low contrast and low signal-to-noise ratio (SNR), the expanded images derived from common methods are not satisfactory. As shown in the analysis of the course from images with low resolution to those with high resolution, the expansion of image is found to be an ill-posed inverse problem. An image interpolation algorithm based on MAP estimation under Bayesian framework is proposed in this paper, which can effectively preserve the discontinuities in the original image. Experimental results demonstrate that the expanded images by this method are visually and quantitatively (analyzed by using the criteria of mean squared error (MSE) and mean absolute error (MAE)) superior to the images expanded by common methods of linear interpolation. Even in expansion of infrared images, this method can also give good results. An analysis about choosing regularization parameter α in this algorithm is given.
100.2000 digital image processing 100.3190 inverse problems 040.3060 infrared A two-section offset quantum-well structure tunable laser with a tuning range of 7 nm was fabricated using offset quantum-well method. The distributed Bragg reflector (DBR) was realized just by selectively wet etching the multiquantum-well (MQW) layer above the quaternary lower waveguide. A threshold current of 32 mA and an output power of 9 mW at 100 mA were achieved. Furthermore, with this offset structure method, a distributed feedback (DFB) laser was integrated with an electro-absorption modulator (EAM), which was capable of producing 20 dB of optical extinction.
130.3120 integrated optics devices 130.5990 semiconductors 230.1480 Bragg reflectors 230.4110 modulators A high power double-clad ytterbium-doped large-mode-area photonic crystal fiber (LMA PCF) laser was demonstrated using a unique Fabry-Perot (F-P) configuration. The pump source is a fiber coupled diode array operating at 976 nm. A continuous wave (CW) output power of 50 W at ~1.04 μm with a slope efficiency of 76.3% is obtained. Single transverse mode operation is achieved without any thermal-optical problems. This laser has the potential for scaling to much higher output power.
140.3480 lasers diode-pumped 140.3510 lasers fiber 060.2430 fibers single-mode A broadband multiwavelength Raman fiber ring laser (RFRL) covering the whole C-band at room temperature are presented. The effect of the intracavity highly nonlinear dispersion-shifted fiber on broadening and flattening the output spectrum envelope is discussed and experimentally demonstrated. More than 45-dB extinction-ratio multiwavelength output from 1527.76 to 1566.86 nm with 100-GHz channel spacing and 2.1-dB power ripple has been achieved by carefully controlling the individual powers of three pump lasers.
060.2320 fiber optics amplifiers and oscillators 060.2330 fiber optics communications A diode-pumped single frequency Tm,Ho:YLF laser operating at an eye-safe wavelength of 2 μm has been developed. Temperature of the laser crystal was controlled at room temperature with a thermoelectric cooler. The line-width narrowing elements were two solid uncoated fused silica etalons whose thicknesses were 1 and 0.1 mm, respectively. Continuous wave single frequency power of 113 mW was obtained.
140.3480 lasers diode-pumped 140.3570 lasers single-mode 140.3580 lasers solid-state 140.0140 lasers and laser optics In this paper, we report a novel 1.3-μm uncooled AlGaInAs/InP multiple quantum well (MQW) ridge waveguide laser diodes. By optimizing the design of MQW structure and facet coatings, together with the application of reversed-mesa ridge waveguide (RM-RWG) structure, polyimide planarization, and lift-off processes technology, an uncooled 1.3-μm, 10-Gb/s directly modulated MQW ridge waveguide laser diode was successfully fabricated. The threshold current and the slope efficiency were 7 mA and 0.48 mW/mA, respectively. The directly modulated bandwidths of 11 and 9.2 GHz were achieved at room temperature and 80 Celsius degrees, respectively.
140.5960 semiconductor lasers 230.5590 quantum-well devices 250.0250 optoelectronics Characterization of Er^(3+)-doped Na2O-WO3-TeO2 glass for ion-exchanged waveguide amplifiers and lasersDownload:739次
Er^(3+)-doped Na2O-WO3-TeO2 glass consistent with standard ion-exchange technology has been fabricated and characterized. The measured absorption and emission spectra of the glass were analyzed by the Judd-Ofelt and McCumber theories. The intensity parameters are Ω2 = 7.01*10^(-20) cm2, Ω4 = 1.80*10^(-20) cm2, Ω6 = 1.03*10^(-20) cm2. The maximum emission cross-section is 0.91*10^(-20) cm2 at 1.533 μm, and a broad 1.5-μm emission spectrum of 65-nm full width at half-maximum (FWHM) is demonstrated. Glass transition temperature, crystallization onset temperature, density, refractive index are also reported for reference in the design and modelling of the ion-exchange process.
160.5690 rare earth doped materials 300.6170 spectra 140.3500 lasers erbium Generation of broadband and multiple-peak THz radiation in aperiodically poled lithium niobateDownload:527次
We theoretically analyze the generation of broadened and multi-peak terahertz (THz) radiation in aperiodically poled lithium niobate (APPLN), whose sequence of opposite domains is optimized by simulated annealing (SA) algorithm. The full-width at half maximum (FWHM) of the broadened THz radiation in our simulation is 0.26 THz. Both of the central wavelength and FWHM can be easily tuned by choosing proper objective functions. THz radiation with wider and flatter FWHM can be achieved by increasing the length of the lithium niobate crystal. The two-peak THz generation is also provided as an example of multi-peak with the central wavelengths at 1.68 and 1.80 THz, respectively.
190.7110 ultrafast nonlinear optics 190.2620 frequency conversion 130.3060 infrared The advantages of multivalued logic in optical parallel computation need no introduction. There are lots of proposals, already reported, where tristate, quarternary state logic operations can be performed with optics. Here we report a new approach to implement tristate logic based all optical flip-flop using optical nonlinear material. The concept and the principle of operation of this type of flip-flop are different from that of the conventional binary one.
190.4360 nonlinear optics devices 210.4680 optical memories 200.3760 logic-based optical processing Three novel kinds of polymers containing rare earth europium have been synthesized and the integrating sphere technique was employed to measure the absolute photoluminescence (PL) efficiency. The PL efficiencies were found to be up to about 40%, which indicates the potential usage in organic light emitting devices (OLED). The energy transfer from ligand to Eu ions and the 5D0 -> 7F2 transition of Eu^(3+) were analyzed under the PL process.
250.5230 photoluminescence 250.3680 light-emitting polymers 310.6860 thin films optical properties An analytical equation, which directly relates amplified spontaneous emission (ASE) with small signal gain (SSG) of travelling-wave semiconductor optical amplifier (TWA), was derived. It was shown by theoretical analysis and experimental results that calibrated ASE spectra of TWA at different injection currents could be good evaluation and extension of SSG near gain peaks when gain peaks are larger than several decibels. The rapid evaluation method of SSG spectra is very simple, effective and especially applicable to batch measurement.
250.5980 semiconductor optical amplifiers 300.6170 spectra 230.7020 traveling-wave devices Experimental observation of the linewidth narrowing of electromagnetically induced transparency resonanceDownload:563次
We report an experimental observation of the variation in linewidth of the electromagnetically induced transparency (EIT) resonance in a three-level Λ-type system for several laser bandwidths in a Rb vapor cell, with and without a buffer gas. It is found, using narrow bandwidth (about 20 kHz) diode laser for both coupling and probe beams, that the linewidth of the EIT resonance can be significantly narrowed in the Rb vapor cell with the buffer gas. The results are in good qualitative agreement with a simple theoretical calculation.
270.0270 quantum optics 270.1670 coherent optical effects Effect of oxygen flow rate on the properties of SiOx films deposited by reactive magnetron sputteringDownload:532次
SiOx (x=0--2) films were deposited on BK-7 substrates by a low frequency reactive magnetron sputtering system with the oxygen flow rate (OFR) changing from 0 to 30 sccm. The samples were characterized by atomic force microscopy, spectrophotometer, and X-ray photoelectron spectroscopy. The extinction coefficient and refractive index decrease, while the optical transmittance increases with the increase of OFR from 0 to 17 sccm. The root mean square surface roughness has a maximum at 10 sccm OFR. The highest deposition rate is at 15 sccm OFR. Our results show that the films deposited at 20 sccm OFR are stoichiometric silica with relatively high deposition rate, low extinction coefficient, and low surface roughness. Therefore, a precise control of OFR is very important to obtain high quality films for optical applications.
310.1860 deposition and fabrication 310.6860 thin films optical properties Optical properties for ZnO thin films grown on (100) γ-LiAlO2 (LAO) substrate by pulsed laser deposition method were investigated. The c-axis oriented ZnO films were grown on (100) γ-LiAlO2 substrates at the substrate temperature of 550 Celsius degrees. The transmittance of the films was over 85%. Peaks attributed to excitons were shown in absorption spectra, which indicated that thin films had high crystallinity. Photoluminescence spectra with the maximum peak at 540 nm were observed at room temperature, which seemed to be ascribed to oxygen vacancy in the ZnO films caused by diffusion of Li from the substrates into the films during the deposition.
250.0250 optoelectronics 310.0310 thin films 040.6070 solid state Effect of nanocrystals on up-conversion luminescence of Er^(3+),Yb^(3+) co-doped glass-ceramicsDownload:547次
Different up-conversion luminescent spectra of Er^(3+) ions were observed in the oxyfluoride glass-ceramics. The ratio of two fluorides in the original compositions was modified in order to form different nanocrystals. The intensity of up-conversion luminescence increased sharply when the ratio of PbF2 and CdF2 was 40:10. The data of differential thermal analysis and X-ray diffraction were used to explain the optimization fluoride ratio. The intensity of up-conversion luminescence is not only decided by the crystallizability but also mainly related with the stoichiometric proportion of fluoride nanocrystals in the glass-ceramics.
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