摘要:

We report the first experimental evidence of a nonlinear optical effect due to intersubband transitions in compositionally asymmetrical multiquantum wells. The effect is detected as an optical rectification signal appearing at the structure terminals when irradiated by a continuous 10.6 &mgr;m CO2laser. The net electro‐optical coefficient of the structure is found to be 7.2 nm/V which is more than three orders of magnitude higher than for bulk GaAs. The results are in good agreement with theoretical predictions.

ISSN:0003-6951    

DOI:10.1063/1.102248

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The spike‐like substructure in picosecond optical pulses from gain‐switched multimode injection lasers is analyzed. A theoretical description based on the interference of the randomly phased longitudinal laser modes and the transient shift of the envelope of the mode spectrum under gain‐switched operation is presented. Single shot, streak camera records and autocorrelation traces are simulated, describing all essential experimental features of the substructure like its random variation from pulse to pulse and inherent periodicity.

ISSN:0003-6951    

DOI:10.1063/1.102249

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A high‐speed optically addressed spatial light modulator is described which uses the electroclinic effect in chiral smecticAliquid crystals with ap‐i‐nphotodiode of hydrogenated amorphous silicon (a‐Si:H). The near microsecond response time is a function of the liquid‐crystal mixture and temperature. We present and analyze optical modulation measurements of a device which exhibits a response time of 40 &mgr;s at 29 °C and 4 &mgr;s at 50 °C. The optical response is continuous and linear with electric field and write‐light intensity, allowing for grey level applications.

ISSN:0003-6951    

DOI:10.1063/1.102250

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

By loading periodic loss perturbation into a GaAlAs/GaAs distributed feedback laser, we have realized complete single longitudinal mode oscillation which is hardly disturbed by cleaved facet reflection. Our coupled‐mode analysis explains this empirical result well.

ISSN:0003-6951    

DOI:10.1063/1.102254

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We show that the nonlinear response of a direct‐gap semiconductor superlattice is greatly enhanced when the separation of the lowest two conduction minibands approaches the magnitude of the principal gap. Two structures exhibiting this enhanced nonlinear response are described.

ISSN:0003-6951    

DOI:10.1063/1.102234

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A method which allows broadband optical detection of ultrasound with large e´tendue from a scattering surface is presented. The wave scattered by the surface interferes with a reference wave which is derived from the scattered wave after stripping it from its optical sidebands by a confocal resonator. Simple implementation by a confocal Fabry–Perot used in reflection is explained and demonstrated experimentally.

ISSN:0003-6951    

DOI:10.1063/1.102235

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A new, very high rate dry etching system based on the plasma jet principle is presented. In this device the active gases are fed into the processing vacuum chamber through a small 0.5 mm i.d. nozzle. By applying radio frequency power (13.56 MHz) a hollow cathode discharge is created inside the nozzle. This discharge will be very intense and effective in dissociating the gas mixture used for reactive etching. A jet stream of radicals will be formed. By placing a silicon substrate in front of this jet stream it is possible to perform very high rate reactive etching of silicon. Etch rates as high as 0.1–0.2 mm/min can be easily obtained. It is demonstrated that the etch rate and the width of the etching crater are sensitive to different processing conditions. The width of the etching crater may be smaller than the diameter of the nozzle exit under certain conditions.

ISSN:0003-6951    

DOI:10.1063/1.102215

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We describe our application of plasma‐enhanced photoemission as aninsituelectrode diagnostic for operating discharge lamps. The method uses focused low‐power laser beams of various wavelengths to investigate emission properties of cathodes in fluorescent lamps. When a pulsed laser beam is directed onto the cathode, the photoemission effect will cause electrons to be ejected ifh&ngr; is greater than the effective work function of the surface over the area illuminated. This burst of photoelectrons can be monitored, as well as the optogalvanic signal which results as they enter the surrounding discharge and produce additional ionization. The photon energy at which photoemission is observed places an upper limit on the local effective work function, which is influenced by the electric field at the cathode surface.

ISSN:0003-6951    

DOI:10.1063/1.102216

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The director configuration in a thin layer of ferroelectric liquid crystal (FLC) under an applied static field is investigated by exciting optic modes in a FLC cell. The reflectivity data obtained may only be fitted to theory by maintaining in the voltage‐distorted optical tensor profile a point in the middle of the cell having the same structure as at 0 V. This unambiguously confirms the chevron structure observed in x‐ray diffraction and shows that the layering remains largely undistorted to fields of order 3×106V m−1.

ISSN:0003-6951    

DOI:10.1063/1.102217

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Thin films of hydrogenated amorphous carbon for magnetic data storage media have been examined by atomic force microscopy. The topography of several coatings has been imaged with a lateral resolution of a few nanometers. Histograms of the height distribution and rms values have been calculated to characterize the roughness of the surfaces quantitatively. Variations of these microscopic properties could be related to changes in the macroscopic behavior like friction and wear.

ISSN:0003-6951    

DOI:10.1063/1.102218

出版商:AIP    

年代:1989

数据来源: AIP