The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Quantum well infrared photodetectors based on the GaAs/AlGaAs material system where the aluminium mole fraction is below 0.45 are used for detecting long wavelength infrared radiation. By increasing the aluminium fraction these detectors can be made to detect shorter wavelengths as well, however this increase degrades detector performance. In this work we have studied a quantum well infrared photodetector...
High-quality nanocrystalline silicon films were fabricated in plasma enhanced chemical vapor deposition system by using a high excitation frequency (40.68 MHz) at low temperatures. It is found that the nanocrystalline Si films with high crystallinity of 89% can be obtained by using SiH4 highly diluted with H2. Furthermore, the area density of the nanocrystalline Si is as high as 4.4×1011/cm2. The...
Methods of calculation of optical absorption and emission spectra for Au8 cluster has been suggested and corresponding calculations has been carried out. It has been shown that the best agreement with experiment is observed in case of planar C2v hexagon+1 shaped structure. The comparison of calculated absorption and emission spectra reveals that Stokes shift is small (about 11.5 nm) which agrees well...
The structural characteristics, deposition rate, absorption spectra and optical band gap of the silicon-germanium thin films, which were prepared by RF-PECVD, had been researched under the diffferent Germane's concentration. By test of Raman, all the silicon-germanium thin films presented amorphous and the spectral peaks were located around 480cm-1. According to the trend of optical band gap, the...
Copper monoxide (CuO) nanorods were successfully synthesized by complex-assisted hydrothermal route. The as-obtained CuO samples were well characterized by XRD, SEM, and TEM. TEM and SEM images showed that the particles have a uniform shape and narrow size distribution. HRTEM and SAED showed that the rod-like CuO nanoparticles were single crystalline monoclinic phase grown along the [110] direction...
Alcohol is estimated to be the major factor of vehicle-related deaths in many counties. Setting-up random checking points with breathalyzer by police departments has several drawbacks: traffic interruption; time consuming; costly; only selected vehicles can be tested; human interaction required. In this paper, a new method based on TDLAS (Tunable Diode Laser Absorption Spectroscopy) for remote detection...
In this paper we investigate the evolutions of Bloch vector in a dense two-level system with near-dipole-dipole (NDD) interactions driven by ultrafast incident pulses, whose duration is far less than the relaxation times. The results show that the evolutionary relationships between dispersion (absorption) and inversion, as function of NDD parameter, are reciprocal. And the pulse width and pulse area...
We present a theoretical study on the spectral linewidth of electromagnetically induced transparency (EIT) in a cyclic three-level atomic system coupled by double coupling fields and a microwave field. The absorption profiles are obtained by a weak probe field scanning corresponding transition. It is shown that for definite Rabi frequencies of interacting fields the spectral linewidth of transparency...
Am at monitoring and forecasting the red tide in real time, an double-wavelength airborne lidar system is proposed in this paper. The lidar system not only can use a infrared laser to detect the seawater scattering signal and gain the information about the red tise's density and size, but also can use a blue-green laser to detect the Brillouin scattering signal and deduce the temperature and salinity...
We confirm firstly to our knowledge that terahertz waves can be guided in a porous fiber with a core of random arrangement of sub-wavelength air holes. Numerical simulations show that many of the properties previously attributed to periodic porous fibers, in particular, low loss and low dispersion, can also be obtained with random porous fibers. We provide that the dispersion can be improved almost...
we present a theoretical study on a four-level atom system with a triplet ground state and an exicited state driven by two coupling fields, a rf field and a probe field. The absorption spectrum is characterized by two EIT. It can be found that the linewidth of the two EIT change with the relative phase of the two coupling fields. The linewidth reaches the minimum when the relative phase is equal to...
Au/Si-NPA composite materials were fabricated by immersion plating method based on a substrate-silicon nanoporous pillar array(Si-NPA). Its surface morphology and optical absorption property were investigated. The optical absorption curves of the samples indicated that compared to pure Au nanoparticles, Surface Plasmon Resonance (SPR) peak of Au nanoparticles in the samples appeared a large blue-shift...
A novel dmit2- complex: [C7H7 (C2H5)3N] [Au (dmit)2 ] (BTEAADT) was synthesized. The thin film of BTEAADT doped into poly (methyl methacrylate) (PMMA) was prepared using spin-coating method. Its third- order nonlinear optical (NLO) properties were investigated using Z-scan technique at the wavelength of 1064 nm with laser pulse duration of 20 ps. The linear optical properties of the thin film were...
Recently, researches about the controllable group velocity of light propagation had made many progresses. And several experiments had demonstrated the signal evolution of slow and fast light. In this letter, the authors described a simple experiment for the tracing of light signals in an erbium-doped optical fiber at the optical communication wavelength firstly. We have, directly, observed the evolution...
Tunable diode laser absorption spectroscopy (TDLAS) technology is a new detective method developed with the combination of a tunable diode laser source and a long absorption path. It has the characteristic of high sensitivity, high precision and rapid response. Based on TDLAS and high performance microcontroller (DSP), the system is developed to monitor the coal mine methane. The second harmonic detection...
Tunable diode laser absorption spectroscopy (TDLAS) is a technique measuring the concentration of trace-gas, the gas concentration is in the sub-ppm (part-per-million) range. Experiment results show that the main part of system noise is interference fringes originating from multiple reflections between surfaces in optical components, so-called etalon effects. This work investigates the basis principle...
Tunable diode laser absorption spectroscopy (TDLAS) is a widely used technique in measuring the concentration of trace gas due to its high sensitivity, high selectivity, and fast time response. The fluctuations of temperature in the gas cell can cause the characteristics of the absorption spectra to change in the TDLAS methane sensing system. The three absorption lines in the R(3) transitions of 2v...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.