摘要:

We study optical properties of ZnMgSSe‐ZnCdSe structures with CdSe submonolayers inserted in a ZnSe matrix. Remarkably high exciton oscillator strength is found in ultrashort‐period submonolayer CdSe‐ZnSe superlattices, as compared to ZnCdSe quantum wells of comparable average width and Cd composition. In conventional ZnCdSe quantum wells the lasing occurs at energies ∼30 meV below the free heavy‐hole exciton transition revealed in photoluminescence and in optical reflectance spectra. In the CdSe submonolayer superlattices lasing occurs at energies in the very vicinity of the heavy hole exciton resonance, directly in the region of strongly‐enhanced exciton‐induced modulation of the reflectance spectrum, and, consequently, refractive index change. We attribute the effects observed to exciton localization by potential fluctuations caused by nanoscale CdSe islands formed during submonolayer deposition. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117430

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The observation of photorefractive two‐wave mixing bistability without external feedback is reported. Hysteresis with an on/off contrast ratio of 30 was obtained through the interaction of two 514.5 nm laser beams within a Fe: KNbO3crystal. A signal beam modulation rate less than 25 mHz was necessary to obtain the hysteresis when the total optical irradiance of the pump and signal beams was ∼1 mW/mm2. The data are shown to correspond well with a two‐state increasing gain model. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117431

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

It is shown that the photorefractive grating produced by a pair of plane waves in periodically poled lithium niobate includes an additional set of spatial harmonics related to the periodic domain structure. This results in new schemes for photorefractive wave coupling. Using the modified phase matching conditions and the concept of optical oscillation we accurately describe the position of the diffraction peaks and explain the main characteristics of self‐organized photoinduced scattering reported recently. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117432

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A transmission silica phase mask grating was used to fabricate LiNbO3wafer phase gratings by a single excimer pulse at 248 nm. The morphologies of the LiNbO3wafer gratings were studied with an atomic force microscope as well as an optical microscope. The crystal structures of the gratings were characterized by x‐ray diffraction and three new crystal phases were found at the gratings’ surface besides the substrate phase of LN (110). ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117433

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Differential reflectance (DR), a contactless optical modulation technique, has been used to study GaAs/AlGaAs quantum wells and bulk GaAs, over a wide temperature range (77<T<600 K). The objective of this study was to demonstrate that DR, unlike most optical modulation spectroscopies, can be effectively and effortlessly used at elevated temperatures, and, thus, provide considerable potential forinsitumonitoring. We have used DR to measure the temperature dependence of several critical points of GaAs and AlxGa1−xAs (x=0.31). ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117434

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Two different upconversion mechanisms leading to green fluorescence in an Er3+doped LiNbO3crystal have been investigated with pulse laser excitations at the wavelengths of 1064 and 980 nm. In the case of the 1064 nm pump, the Er3+ions become excited by the phase‐matched second harmonic wave generated in the LiNbO3crystal, whereas sequential two‐photon absorption is mainly responsible for the excitation with the 980 nm pump. The second harmonic excitation is of an order of magnitude more efficient than the sequential two photon excitation in the upconversion of the near‐infrared pump photons to the green fluorescence. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117435

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Direct measurements of the electric field in the sheath of adcglow discharge were made using laser spectroscopic measurements of argon atoms. The effect of the electric field on the 4s⇒7ftransitions was used to determine the electric field. Both laser opto‐galvanic spectra and laser‐induced fluorescence spectra were obtained. The magnitude of the electric field was determined using an experimentally obtained calibration of the change in wavelength produced by the electric field. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117436

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An arc‐heated source for producing an intense nitrogen atom beam with intensity of 1019atoms/sr s and kinetic energies of 0.5–4 eV is presented. The arc discharge has been carried out in pure nitrogen gas and maintained stable in an arc operating pressure of 30–300 Torr. The beam kinetic energy changes with the arc pressure, and is insensitive to the arc current. Auger electron spectroscopy analysis showed that a TiNO layer with a thickness of about 100 A˚ was formed on the smooth Ti wafer at room temperature with interaction of the atomic nitrogen beam. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117437

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A simple technique is presented for evaluating defect profiles in ultrathin Si films on buried SiO2formed by implanted oxygen. A combination of thinning by sacrificial oxidation and epitaxial film growth by UHV‐CVD is used. By measuring the defect density of the epitaxial film with respect to the thickness prior to epitaxial growth, the profile of the initial defect density can easily be evaluated. This technique is applied to evaluate the Si on insulator structure fabricated by state‐of‐the‐art technique, in which low dose oxygen implantation (∼4×1017cm−2) and high temperature internal oxidation processes are used. The defect density at the surface of the film is 250 cm−2. However, as the buried interface is approached, the defect density increases. The defect density at 20 nm from the buried interface is as high as 6×105cm−2. A defect generation mechanism is also discussed. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117438

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

B as well as N core excitation spectra of hexagonal boron nitride (h‐BN) have been studied by means of x‐ray Raman scattering (XRS) spectroscopy. Transitions from 1score to &sgr;* and &pgr;* states are completely distinguished by anisotropy measurements of XRS, thus making an unambiguous assignment to the symmetries of excited states and offering a sound basis to characterizeh‐BN with core absorption spectroscopy. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117439

出版商:AIP    

年代:1996

数据来源: AIP