RESUMEN
Grating coupled semiconductor lasers (GCSLs) has a wide application prospect in many fields, such as optical free space communication, intersatellite communication, ranging for laser radar, atmospheric environmental testing and medical imaging. In order to verify the reliability of GCSLs, the chips in different preparation stages and products of GCSLs are tested based on Raman spectroscopy. It concluded that for unprocessed semiconductor laser chip, the longitudinal optical (LO) photons mode vibration of GaAs chip is strong but the transverse (TO) optical photons mode vibration of GaAs chip is weak. when the is unprocessed. When the surface of GaAs chip is covered by a layer of SiO2 membrane, the LO mode will movetowards long wavelength direction, but its intensity wouldn't change. When a 100 m mesa is etched on GaAs chip which is covered by SiO2 membrane, LO mode vibration of GaAs chip weakens and TO mode vibration of GaAs chip enhances, and the peak width of LO mode and TO mode increase. After gratings are etched on the 100 m mesa, LO mode vibration of GaAs chip continues to weaken, but TO mode vibration of GaAs chip becomes stronger. It shows that lattice defects exist in the fabrication process of GCSLs. By contrast testson the semiconductor lasers without gratings, it shows that defect peaks present in the Raman spectrum of GCSLs regardless of the defects on light emitting surface. This further proved that the strains or defects were introduced into the fabrication process of grating structure, which affects its reliability, resulting in a decrease of the reliability of GCSLs.
RESUMEN
Fermi resonance is a phenomenon of molecular vibrational coupling and energy transfer occurred between different groups of a single molecule or neighboring molecules. Many properties of Fermi resonance under different external fields, the investigation method of Raman spectroscopy as well as the application of Fermi resonance, etc need to be developed and extended further. In this article the research results and development about Fermi resonance obtained by Raman spectral technique were introduced systematically according to our work and the results by other researchers. Especially, the results of the behaviors of intramolecular and intermolecular Fermi resonance of some molecules under some external fields such as molecular field, pressure field and temperature field, etc were investigated and demonstrated in detail according to the Raman spectra obtained by high pressure DAC technique, temperature variation technique as well as the methods we planed originally in our group such as solution concentration variation method and LCOF resonance Raman spectroscopic technique, and some novel properties of Fermi resonance were found firstly. Concretely, (1) Under molecular field. a. The Raman spectra of C5H5 N in CH3 OH and H2O indicates that solvent effect can influence Fermi resonance distinctly; b. The phenomena of the asymmetric movement of the Fermi resonance doublets as well as the fundamental involved is tuned by the Fermi resonance which had not been found by other methods were found firstly by our variation solution concentration method; c. The Fermi resonance properties can be influenced distinctly by the molecular group reorganization induced by the hydrogen bond and anti-hydrogen bond in solution; d. Fermi resonance can occurred between C7 H8 and m-C8H10, and the Fermi resonance properties behave quite differently with the solution concentration; (2) Under pressure field. a. The spectral lines shift towards high wavenumber with increasing pressure, and frequency difference Δ varies with pressure, which induced the change of W; b. The W of νi + ν4 ν3 of CCl4 in C6H6 decreased more quickly in solution than in pure liquid with increasing pressure and the Fermi resonance disappeared ahead of that in pure liquid, which indicates that the phenomenon of Fermi resonance induced by pressure effect can reveal the mechanism of some solvent effects. (3) Under temperature field. a. The Fermi resonance properties of different molecules behave quite differently with temperature. For an instance, the one of CO2 can be influenced distinctly by temperature, while the one of CS2 behaves no change with temperature. This article offers systematic theoretical and experimental support to the investigation of identification and assignment of molecular spectral line, the confirmation of molecular conformation and conformers, the effect of hydrogen bond on molecular structure and properties, etc.
RESUMEN
Stimulated Raman scattering was studied in water and heavy water using pulse laser at the wavelength of 532nm, not only obtaining the stimulated Raman of O-H and O-D stretching vibration, but also obtaining the stimulated Raman lattice vibration. When the laser energy was 130 mJ, the low frequency Stokes and anti-Stokes 313 cm(-1) line of water could be observed; When the laser energy was 160 mJ, the low frequnecy Stokes and anti-Stokes 280 cm(-1) line of heavy water could be observed. The results were explained by physics mechanism of laser induced plasma.
RESUMEN
Raman spectra of ice VII phase were obtained at room temperature when the pressure was from 2.5 to 23 GPa. The experimental results indicate that the oxygen atoms distance do-o of ice decreased with pressure increasing,which results in that hydrogen bond is shortened, O--H bond is lengthened,force constant is reduced, and Raman spectra are red shifted. The orientation order of proton (hydrogen atom) is first increased and then decreased with varying the pressure, which leads to the Raman intensity increasing and then decreasing, and Raman linewidth is decreased and then increased, and the linewidth is the least when the pressure is 13 GPa.
RESUMEN
In this paper, we explore whether interparticle spacing affects steady-state and transient-state optical properties by comparing close-packed CdSe/ZnS-quantum dots (QDs) and CdSe/ZnS-QDs dispersed in polymethyl methacrylate (PMMA). High-pressure is an effective physical means to adjust the interparticle spacing of QDs, which may artificially expand the application of QDs further. The results under high-pressure indicate that it is the reduced interparticle spacing rather than the enhanced quantum confinement effect with volume compression that has a stronger effect on exciton relaxation of CdSe/ZnS-QDs. This work is hoped to help us further understand the effect of interparticle spacing among QDs in various integrated environments.
RESUMEN
Ten meter single mode silica fiber was used to study the temperature characteristics of stimulated Raman scattering (SRS), and additional peaks (double-humped structure) were observed at both sides of pump light and first-order Stokes light in the experiment. The peak intensity increased first, and then decreased as the temperature increased from 80 K to 295 K. The first-order Stokes double-humped wave peaks disappeared when the temperature was 295 K. The double-humped peaks phenomenon was caused by simulated four photon mixing (SFPM), according to stimulated four-photon mixing theoretical calculation. At the same time, the phenomenon that the frequency shift of first-order Stokes spectrum line in SRS increased from 706.9 to 712.9 cm(-1) and its half width increased from 1.75 to 2.18 nm was theoretically explained, and the theoretical results are well consistent with experiments.
RESUMEN
Lycopene and beta-carotene are two important nutritional components in tomato. The main Raman spectrum group of lycopene and beta-carotene abundant in tomato is identical and difficult to be distinguished through fundamental frequency. With excitation wavelength of 514.5 nm, the excited light was just present in the half width range of the main absorption bands of Lycopene and beta-carotene, so the resonance Raman effect can occur. Based on resonance Raman spectra, by on-body measuring the second harmonic of stretching vibration of carbon-carbon conjugated double bond in lycopene and beta-carotene, the content of lycopene and beta-carotene can be obtained according to the integrated intensity of each component calculated by software. And this provides a method for on-body determining the content of the components with the homologous group.