Temperature and Polarization Dependence of the Optical Absorption in ZnGeP2 at two Micrometers

1993 ◽  
Vol 325 ◽  
Author(s):  
M. Shah ◽  
M. C. Ohmer ◽  
D. W. Fischer ◽  
N. C. Fernelius ◽  
M. O. Manasreh ◽  
...  
Keyword(s):  
Optical Absorption ◽  
Absorption Coefficient ◽  
Polarization Dependence ◽  
Type I ◽  
Optical Parametric Oscillators ◽  
Absorption Coefficients ◽  
Parametric Oscillators ◽  
The Face ◽  
Significant Temperature ◽  
First Time

AbstractThe temperature and polarization dependence of the optical absorption in ZnGeP2 at two micrometers is reported for the first time over the temperature range from 10K to 300K. The radiation was normally incident upon the face of a cubic sample which contained the c-axis. The absorption of o-rays (E parallel to c), and erays (E perpendicular to c) was determined. It was found that the e-ray absorption coefficient was always significantly larger than the o-ray absorption coefficient and that it had a less significant temperature dependence. For example, the ratio of e-ray to o-ray absorption coefficient was approximately two at 300K and five at 77K. Correspondingly the o-ray absorption coefficients were reduced upon cooling to 77K by a factor of 2.5, while the e-ray absorption coefficients were reduced only slightly (10%-20%). These results indicate that for Type I optical parametric oscillators (OPOs) which use an oray pump beam, that performance may be improved by cooling the crystal.

Degenerate type I nanosecond optical parametric oscillators

2003 ◽  
Vol 20 (11) ◽  
pp. 2319 ◽  
Author(s):  
Arlee V. Smith ◽  
Darrell J. Armstrong ◽  
Mark C. Phillips ◽  
Russell J. Gehr ◽  
Gunnar Arisholm
Keyword(s):  
Type I ◽  
Optical Parametric Oscillators ◽  
Parametric Oscillators ◽  
Optical Parametric ◽  
Degenerate Type

scholarly journals Case Report: Aicardi-Goutières Syndrome Caused by Novel TREX1 Variants

2021 ◽  
Vol 9 ◽  
Author(s):  
De Wu ◽  
Liwei Fang ◽  
Ting Huang ◽  
Songcheng Ying
Keyword(s):  
White Matter ◽  
Type I Interferons ◽  
Enzyme Linked Immunosorbent Assay ◽  
Type I ◽  
White Matter Volume ◽  
Elevated Type ◽  
Chinese Girl ◽  
The Face ◽  
Exonuclease 1 ◽  
First Time

TREX1 (three prime repair exonuclease 1) gene encodes DNA 3′ end repair exonuclease that plays an important role in DNA repair. Mutations in TREX1 gene have been identified as the cause of a rare autoimmune neurological disease, Aicardi-Goutières syndrome (AGS). Here, we report an AGS case of a 6-month-old Chinese girl with novel TREX1 variants. The patient had mild rashes on the face and legs, increased muscle tensions in the limbs, and positive cervical correction reflex. Cranial magnetic resonance imaging showed that there were patches of slightly longer T1 and T2 signals in the bilateral cerebral hemisphere and brainstem white matter, mainly in the frontotemporal lobe, together with decreased white matter volume, enlarged ventricles, and widened sulcus fissure. Total exon sequencing showed that the TREX1 gene of the child had mutations of c.137_138insC and c.292_293insA, which had not been reported before. In addition, elevated type I interferons were detected by using enzyme-linked immunosorbent assay in the patient's serum. Together, our study demonstrated that novel TREX1 variants (c.137_138insC and c.292_293insA) cause AGS for the first time.

Nonlinear Intersubband Optical Absorption Coefficient and Refractive Index Changes in Asymmetric Parabolic Double Quantum Wells

2017 ◽  
Vol 6 (1) ◽  
pp. 121-125 ◽  
Author(s):  
Menberu Mengesha Woldemariam
Keyword(s):  
Refractive Index ◽  
Optical Absorption ◽  
Absorption Coefficient ◽  
Quantum Wells ◽  
Optical Absorption Coefficient ◽  
Double Quantum ◽  
Absorption Coefficients ◽  
Total Change ◽  
Left Handed ◽  
Index Changes

The change in optical absorption coefficients and refractive index in GaAs-AlGaAs asymmetric parabolic double quantum wells (DQWs) with applied electric field are studied in detail. Analytical expressions for the linear, nonlinear and total intersubband absorption coefficient and refractive index changes are obtained by using compact density matrix approach. It is found that the magnitude of the nonlinear part of the change in refractive index and absorption coefficients are larger than the linear part in the given frequency region. The value of the total change in refractive index is negative and the asymmetric DQWs becomes left handed media. This property is of great importance for metamaterials science and can contribute substantially to the present search for simple and inexpensive left handed media. Moreover the negative value of the total change in absorption coefficient may be used for developing optical device such as maser at different frequency regime.

scholarly journals A2AgCrBr6 (A = K, Rb, Cs) and Cs2AgCrX6(X = Cl, I) Double Perovskites: A Transition-Metal-Based Semiconducting Material Series with Remarkable Optics

Nanomaterials ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 973 ◽  
Author(s):  
Pradeep R. Varadwaj
Keyword(s):  
Transition Metal ◽  
Optical Absorption ◽  
Absorption Coefficient ◽  
Dielectric Function ◽  
Density Of States ◽  
Dielectric Constants ◽  
Double Perovskites ◽  
Absorption Coefficients ◽  
Band Structures ◽  
Effective Masses

With an interest to quest for transition metal-based halogenated double perovskites AB′B″X6 as high performance semiconducting materials for optoelectronics, this study theoretically examined the electronic structures, stability, electronic (density of states and band structures), transport (effective masses of charge carriers), and optical properties (dielectric function and absorption coefficients, etc.) of the series A2AgCrBr6 (A = K, Rb, Cs) using SCAN + rVV10. Our results showed that A2AgCrBr6 (A = Rb, Cs), but not K2AgCrBr6, has a stable perovskite structure, which was revealed using various traditionally recommended geometry-based indices. Despite this reservation, all the three systems were shown to have similar band structures, density of states, and carrier effective masses of conducting holes and electrons, as well as the nature of the real and imaginary parts of their dielectric function, absorption coefficient, refractive index, and photoconductivity spectra. The small changes observed in any specific property of the series A2AgCrBr6 were due to the changes in the lattice properties driven by alkali substitution at the A site. A comparison with the corresponding properties of Cs2AgCrX6 (X = Cl, I) suggested that halogen substitution at the X-site can not only significantly shift the position of the onset of optical absorption found of the dielectric function, absorption coefficient and refractive spectra of Cs2AgCrCl6 and Cs2AgCrI6 toward the high- and low-energy infrared regions, respectively; but that it is also responsible in modifying their stability, electronic, transport, and optical absorption preferences. The large value of the high frequency dielectric constants—together with the appreciable magnitude of absorption coefficients and refractive indices, small values of effective masses of conducting electrons and holes, and the indirect nature of the bandgap transitions, among others—suggested that cubic A2AgCrBr6 (A = Rb, Cs) and Cs2AgCrCl6 may likely be a set of optoelectronic materials for subsequent experimental characterizations.

Nonlinear optical absorption in the core shell nanowire

2017 ◽  
Vol 31 (23) ◽  
pp. 1750164 ◽  
Author(s):  
Mohammad Kouhi
Keyword(s):  
Refractive Index ◽  
Relaxation Time ◽  
Optical Absorption ◽  
Absorption Coefficient ◽  
Shell Thickness ◽  
Refractive Index Change ◽  
Resonance Wavelength ◽  
Core Shell ◽  
Core Radius ◽  
Absorption Coefficients

In this paper, the effect of incident light intensity, relaxation time, core radius and shell thickness on linear, nonlinear, total optical absorption coefficients and refractive index changes in [Formula: see text] core–shell nanowire are theoretically investigated. The presented nanostructure is a cylindrical quantum wire including a shell around the cylinder core. By numerical solution of Schrödinger equation in the cylindrical coordinates with effective mass approximation, the optical absorption coefficients are calculated. The results show that the magnitude of optical absorption coefficients can be adjusted by varying the relaxation time. The positions of resonant peaks of optical absorption coefficients are redshifted by increase of core radius due to decrease of the energy difference between two energy levels. With increase of shell thickness initially, the resonance wavelength of absorption coefficient increases (redshift) and magnitude of absorption coefficient decreases. Then with more increases of the shell thickness, redshifting of resonance wavelength is stopped and magnitude of absorption coefficient is increased. There is a significant increase in the refractive index change with increase of relaxation time.

scholarly journals Modelling Dispersion Compensation in a Cascaded-Fiber-Feedback Optical Parametric Oscillator

Optics ◽  
2021 ◽  
Vol 2 (2) ◽  
pp. 96-102
Author(s):  
Ewan Allan ◽  
Craig Ballantine ◽  
Sebastian C. Robarts ◽  
David Bajek ◽  
Richard A. McCracken
Keyword(s):  
Pulse Propagation ◽  
Dispersion Compensation ◽  
Numerical Aperture ◽  
Tunable Laser ◽  
High Energy ◽  
Order Effects ◽  
Optical Parametric Oscillators ◽  
Fiber System ◽  
Parametric Oscillators ◽  
Optical Parametric

Fiber-feedback optical parametric oscillators (OPOs) incorporate intracavity fibers to provide a compact high-energy wavelength-tunable laser platform; however, dispersive effects can limit operation to the sub-picosecond regime. In this research article, we modeled pulse propagation through systems of cascaded fibers, incorporating SMF-28 and ultra-high numerical aperture (UHNA) fibers with complementary second-order dispersion coefficients. We found that the pulse duration upon exiting the fiber system is dominated by uncompensated third-order effects, with UHNA7 presenting the best opportunity to realise a cascaded-fiber-feedback OPO.

Healthcare and Terrorism: The Lebanese Experience

2021 ◽  
pp. 1-4
Author(s):  
Nooreddine Iskandar ◽  
Tatiana Rahbany ◽  
Ali Shokor
Keyword(s):  
Public Health ◽  
Qualitative Study ◽  
Thematic Analysis ◽  
Terrorist Attacks ◽  
Analysis Method ◽  
Structured Interviews ◽  
Security Issues ◽  
The Face ◽  
The Common ◽  
First Time

Abstract Background: Due to the common instability caused by political and security issues, Lebanese hospitals have experienced acts of terrorism multiple times. The most recent Beirut Explosion even forced several hospitals to cease operations for the first time in decades—but studies show the preparedness levels for such attacks in similar countries are low. Objective: The aim of this study is to explore the experience of Lebanese hospitals with terrorist attacks. Methods: This qualitative study used semi-structured interviews with various stakeholders to assess their experience with terrorist bombings. Data was analyzed using the thematic analysis method. Results: The researchers found that Lebanese hospitals vary greatly in their structures and procedures. Those differences are a function of 3 contextual factors: location, culture, and accreditation status. Hospitals found near ‘dangerous zones’ were more likely to be aware and to have better response to such events. A severe lack of communication, unity of command, and collaboration between stakeholders has made the process fragmented. Conclusion: The researchers recommend a larger role for the Ministry of Public Health (MOPH) in this process, and the creation of a platform where Lebanese organizations can share their experiences to improve preparedness and resilience of the Lebanese healthcare system in the face of terrorism.

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