Pressure Dependence Of Refractive Index Research Articles

Monodisperse Gold Nanorods for High-Pressure Refractive Index Sensing.

The effects of hydrostatic pressure on the surface plasmon resonances (SPRs) of aqueous dispersions of monodisperse gold nanorods (AuNRs)were determined up to 9 GPa. The ultranarrow longitudinal SPR band of monodisperse AuNRs allows us to monitor a gradual red shift with pressure, which shows abrupt jumps at the liquid to ice phase VI and ice phase VII transitions. Despite solidifying at low pressure (∼1.8 GPa), water displays a regime of quasi-hydrostaticity in said phases VI and VII, up to ca. 5 GPa. Above this pressure, nonhydrostatic effects manifest themselves through broadening of the SPR bands, but barely any effect is observed on the position of the surface plasmon mode. The variation in the SPR peak wavelength with pressure allowed us to determine the pressure dependence of the refractive index of water. Unlike Brillouin scattering or interferometric techniques, this plasmon-spectroscopy-based method leads to a more direct determination of the refractive index, which is well described empirically by Murnaghan-type equations in the three explored phases. We report herein the obtained analytical functions providing the pressure dependence of refractive index in the liquid, ice VI, and ice VII phases of water.

Pressure dependence of refractive index, dielectric constants and optical phonon frequencies of indium arsenide

A pseudopotential approach has been employed so as to investigate the pressure dependence of refractive index, dielectric constants and optical phonon frequencies for InAs. At zero pressure our findings are compared to those reported in the literature and found to be generally in reasonably good agreement. The pressure dependence of all features of interest showed a monotonic behavior. The linear pressure coefficient of the refractive index and dielectric constants are calculated and reported. The transverse and longitudinal optical phonon frequencies are found to shift towards high frequencies when pressure is applied.

Pressure dependence of refractive index of Ge near the absorption edge

Pressure-dependent refractive index of semiconductor germanium (Ge) near the absorption edge has not been well studied theoretically and experimentally to date. In this paper, we present a pressure-dependent refractive index of Ge film near its absorption threshold (about 1550 nm), deduced from the reflectivity of high crystalline Ge film coated on a fiber end. The thin Ge layer is deposited on one end of an optical fiber by using an E-beam evaporation machine equipped with a substrate heater of a quartz halogen lamp. In order to obtain high crystalline film, the quartz halogen lamp heater provides a constant substrate temperature of 450 ℃ during film deposition. After the film forming, the sample is transferred into a muffle furnace with a nitrogen atmosphere and annealed at 600 ℃ for 20 h to guarantee the formation of higher crystalline film. The process of light propagating through the optical fiber and reflecting from the Ge thin-film involves multi-beam interference. An abnormal dispersion is observed in the refractive index spectra of the polycrystalline Ge near the absorption edge. A comparison shows that the refractive index spectrum of the amorphous Ge is normal dispersion. Unlike previously reported results that the pressure-dependent refractive index had a negative value, in our experiment it is observed to be a positive value near the absorption edge. To better understand this phenomenon, we use a critical point model including the pressure effect to successfully fit the experimental data. We obtain an abnormal dispersion range of 1505-1585 nm and a range of negative value of pressure-dependent refractive index of 1500-1580 nm from the critical point model. In this paper, we adopt the method of high crystalline Ge film coated on a fiber end. This method has the advantages of small volume, high precision and strong stability, which can be used to measure the optical properties of many thin film materials under the different conditions (temperature, electric field or magnetic field, etc.). In this work, we obtain the refractive index of the Ge film and its pressure dependence near the C-band of the optical fiber communication, and these results are conducive to optimized design of the Ge-based optical systems near the C-band of the optical fiber communication.

Refractive indices and related properties of some potential mixed crystals

The high frequency refractive indices of some binary, ternary and quaternary mixed crystals have been evaluated from the knowledge of plasmon energy and the lowest gap energy of the crystals for their applications in heterojunctionled and solar cells. The Fermi energy screening factor correction has been applied to effect accuracy in prediction. The model has been used to study the temperature and pressure dependence of refractive index. The calculated value agrees with experiment (within a few percent) justifying the validity of the model.

STUDYING THE LAWS OF DEPENDENCE OF REFRACTIVE INDICES OF AMORPHOUS As2S3 ON HYDROSTATIC PRESSURE USING HIGH-PRESSURE MICROSPECTROSCOPIC SYSTEM

The pressure and wavelength dependence of refractive indices of amorphous As2S3 have been studied by means of observing transmission light interference spectrum under room temperature with the high-pressure microspectroscopic system in conjunction with the gasketed diamond anvil cell, in which methanol-ethanol mixture was used as pressure liquid with hydrostatic pressure up to 66kbar and wavelength between 400-900 nm. The pressure was monitored by ruby R-line shift. Amorphous As2S3 thin film samples a few micrometers in thickness were prepared by vacuum evaporation. Under our experimental conditions, neither the light of 441.6 nm He-Cd laser used for excitation of the ruby gauge, nor that of the Br-W lamp for measurement of light transmission, showed any detectable influence on the optical properties of the sample.By observing the interference maxima at energies below the absorption threshold and using the results of. Gerlich et al. of the pressure dependence of volume of a-As2S3, the pressure dependence of refractive index between 500-850 nm have been determined. The refractive index of amorphous As2S3 is significantly pressure-sensitive, increasing by 35% at 650 nm with pressure change of 66 kbar. Analysis of experimental data by least-square method on the computer gives the coefficients of the nonlinear formula n(p)=n(0)+Ap+Bp2, where n(p) and n(0) are refractive indices at pressure p and 1 bar, respectivelly; coefficients A and B are relative to wavelength, for example {A=9.62×10-3 kbar-1,B=2.07×10-3 kbar-2, for wavelength) λ = 800nm and other values were given in the paper. This relationship is different from the results of Weinstein et al. and Galkiewicz et al., where linear relationship between n and p at fixed wavelength in infra-red regime was reported. The difference, however, may be attributed to the different method of sample preparation etc.