IMPROVEMENT IN FIGURE OF MERIT BY DOPING FOR SQUEEZED STATE GENERATION IN GaAs

A simplistic theoretical investigation based upon the free electron model of optical nonlinearities has been made to establish the superiority of a doped semiconductor over its intrinsic counterpart in efficient squeezed state generation. Choice of Doping level at a given operating frequency regime has to be carefully choosen to avoid free carrier absorption and scattering losses. The relevant figure of merit is found to favor a doped crystal duly shined by off-resonant low frequency laser as a potential scheme to achieve significant quadrature variance. Numerical calculations have been made for GaAs sample irradiated with 10.6 μm pulsed CO 2 laser of intensity ~ 1.6 × 102 GW/m 2.

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The conduction bands in 6H and 15R silicon carbide II. Absorption measurements

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1967.0145 ◽

1967 ◽

Vol 299 (1458) ◽

pp. 393-404 ◽

Cited By ~ 25

Keyword(s):

Relaxation Time ◽

Effective Mass ◽

Low Frequency ◽

Free Carrier ◽

Frequency Region ◽

Free Carrier Absorption ◽

Absorption Coefficients ◽

High Frequency Region ◽

Low Frequencies ◽

Carrier Absorption

It is shown, on the basis of classical theory, that the free carrier absorption in a uniaxial semiconductor having an anisotropic effective mass and relaxation time is characterized by two independent absorption coefficients. For a general multivalley model these absorption coefficients are shown to be quite complicated functions of the effective mass and relaxation time tensors; these functions are considerably simplified if the energy band extrema are located on the symmetry axis. In this case the anisotropy of the effective mass and also that of the relaxation time may be obtained from the free carrier absorption coefficients if these are measured at high frequencies (w 2 >r 2 ≫ 1) and also in the low frequency region (w 2 r 2 ≪ 1) in the same specimen. At low frequencies the free carrier absorption coefficients no longer have a near quadratic dependence upon wavelength but tend to limiting values. Results of measurements in the high frequency region are presented for a number of samples of both the 6H and 15R forms of silicon carbide. At wavelengths for which the absorption is due to free carriers the absorption coefficient for radiation with its electric vector (X) perpendicular to the symmetry axis (c axis) is greater than that for X || c by a factor of ˜ 4 in the 15R polytype and by a factor of ˜ 15 in the 6H form. The wavelength dependences of the absorption coefficients in the high-frequency region are discussed in terms of the probable scattering mechanisms. In one specimen of each polytype the m easurem ents were extended to ˜ 20 μm and the absorption coefficients were observed to approach limiting values as predicted by the theoretical expressions for low frequencies. Quite good agreement was found between the magnitudes of the calculated and observed absorption coefficients, and the onset of low-frequency behaviour was found to occur in approximately the wavelength region predicted by classical theory. From these results the effective m ass in the direction of sym m etry axis was found to be 1.5 ± 0*2 m 0 in the 6H polytype and ˜ 0-53 m 0 in the 15R polytype; the relaxation time appropriate to the axial direction was found to be greater than that for the transverse plane by a factor of 2.5 in the 6H form and 1.6 in the 15R form. Additional absorption bands for X ||c were found at 19.9 μm in 6H SiC and a t 17.5 μm in the 15R polytype and were of magnitude ca . 100 cm -1 and ca . 150 cm -1 respectively; their origin is as yet unknown. All the results reported relate to room temperature.

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4-QAM OFDM Data Switching via Free Carrier Absorption in Si-Rich SiC Waveguide

IEEE Journal of Selected Topics in Quantum Electronics ◽

10.1109/jstqe.2020.3033282 ◽

2021 ◽

Vol 27 (3) ◽

pp. 1-11

Author(s):

Yen-Wei Hsueh ◽

Chih-Hsien Cheng ◽

Cai-Syuan Fu ◽

Huai-Yung Wang ◽

Bo-Ji Huang ◽

...

Keyword(s):

Free Carrier ◽

Free Carrier Absorption ◽

Carrier Absorption ◽

Data Switching

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Microscopic FCA System for Depth-Resolved Carrier Lifetime Measurement in SiC

Materials Science Forum ◽

10.4028/www.scientific.net/msf.924.269 ◽

2018 ◽

Vol 924 ◽

pp. 269-272 ◽

Cited By ~ 2

Author(s):

Shinichi Mae ◽

Takeshi Tawara ◽

Hidekazu Tsuchida ◽

Masashi Kato

Keyword(s):

Carrier Lifetime ◽

Laser Light ◽

Probe Laser ◽

Free Carrier Absorption ◽

Cross Sectional ◽

Lifetime Measurements ◽

Control Distribution ◽

System A ◽

Excitation Laser ◽

Carrier Absorption

For high voltage SiC bipolar devices, carrier lifetime is an important parameter, and for optimization of device performance, we need to control distribution of the carrier lifetime in a wafer. So far, there have been limited systems for depth-resolved carrier lifetime measurements without cross sectional cut. In this study, we adopted a free carrier absorption technique and made local overlapping of the probe laser light with excitation laser light to develop depth-resolved carrier lifetime measurements. We named the developed system a microscopic FCA system and demonstrated measurement results for samples with and without intentional carrier lifetime distribution.

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Influence of Li2CO3 addition on electrical and magnetic properties of Ni0.6Mg0.4Fe2O4

Journal of Advanced Dielectrics ◽

10.1142/s2010135x20500034 ◽

2020 ◽

Vol 10 (03) ◽

pp. 2050003

Author(s):

M. R. Hassan ◽

M. T. Islam ◽

M. N. I. Khan

Keyword(s):

Magnetic Properties ◽

Single Phase ◽

Low Frequency ◽

Solid State Reaction Method ◽

Charge Carriers ◽

X Ray Diffraction ◽

X Ray ◽

Electrical And Magnetic Properties ◽

Frequency Regime ◽

Xrd Patterns

In this research, influence of adding Li2CO3 (at 0%, 2%, 4%, 6%) on electrical and magnetic properties of [Formula: see text][Formula: see text]Fe2O4 (with 60% Ni and 40% Mg) ferrite has been studied. The samples are prepared by solid state reaction method and sintered at 1300∘C for 6[Formula: see text]h. X-ray diffraction (XRD) patterns show the samples belong to single-phase cubic structure without any impurity phase. The magnetic properties (saturation magnetization and coercivity) of the samples have been investigated by VSM and found that the higher concentration of Li2CO3 reduces the hysteresis loss. DC resistivity increases with Li2CO3 contents whereas it decreases initially and then becomes constant at lower value with temperature which indicates that the studied samples are semiconductor. The dielectric dispersion occurs at a low-frequency regime and the loss peaks are formed in a higher frequency regime, which are due to the presence of resonance between applied frequency and hopping frequency of charge carriers. Notably, the loss peaks are shifted to the lower frequency with Li2CO3 additions.

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A study of vibrations of boron and phosphorus in silicon by infra-red absorption

Proceedings of the Royal Society of London Series A - Mathematical and Physical Sciences ◽

10.1098/rspa.1965.0169 ◽

1965 ◽

Vol 287 (1408) ◽

pp. 64-88 ◽

Cited By ~ 67

Keyword(s):

Second Harmonic ◽

Force Constants ◽

Published Data ◽

Free Carrier Absorption ◽

Local Modes ◽

Pure Silicon ◽

Infra Red ◽

Carrier Absorption ◽

Experimental Problem ◽

Silicon Doped

The infra-red absorption spectrum of silicon doped with high densities of boron and phosphorus has been measured from 1 to 60 μm and at temperatures between 5 and 290 °K in order to observe the local and band mode vibrational absorption activated by these impurities. The major experimental problem, that of achieving a high degree of electrical compensation to eliminate free carrier absorption, was solved by using fast electron bombardment to introduce a controllable number of trapping centres. A series of experiments was conducted to eliminate the effects of these centres from the spectrum of the chemical impurities. The characteristic spectra of the substitutional boron and phosphorus have been analysed in detail in terms of the theory of Dawber & Elliott. For local modes activated by boron isotopes close agreement with theory has been found in number of lines, strength and frequency. From the latter it is estimated that the local force constants are weakened by less than 10 % on substituting boron for silicon in the lattice. Second harmonic lines are observed at a frequency 0.25 % less than twice that of the fundamentals. The band modes exhibit a striking in-band resonance at 0.0546 eV which was not theoretically predicted. This is attributed to phosphorus and analysis shows that the theory can give such a resonance but not with parameters associated with substitutional phosphorus and unchanged force constants. Most of the remaining features in the band modes can be interpreted satisfactorily in terms of substitutional boron but this requires some modification to published data on the density of states for pure silicon. Critical points for TO( L ), TO( X ) and LA( L ) phonons are clearly identified in the spectra.

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