摘要:

The macroscopic third‐order nonlinearity &Ggr; of a nematic liquid crystal has been measured for the first time with the technique of dc electric‐field‐induced optical second‐harmonic generation. The effect of nematic ordering on &Ggr; is observed. Results are in good agreement with theoretical calculations.

ISSN:0003-6951    

DOI:10.1063/1.90821

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Piezoelectric (PZE) oscillations superimposed on the pyroelectric (PRE) voltage response to short (<50 nsec) single CO2laser pulses in PLZT detectors are shown to have an incubation time, i.e., to startafterthe beginning of the PRE response. During the incubation time (40–60 nsec, depending on sample geometry) the PRE response is not disturbed, thus PRE detectors for use with short ir pulses can be designed with minimum PZE interference. The initial PZE amplitudes were 0.05–0.4 of the observed peak PRE voltages. The periods of the PZE oscillations with the measured lengths of the samples gave 2.2 km/sec for the velocity of sound in PLZT.

ISSN:0003-6951    

DOI:10.1063/1.90822

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An x‐ray step‐scanning topographic technique combined with an automatic Bragg‐angle control (ABAC) system has been developed and applied to the study of crystal perfection of silicon wafers subjected to copper decoration, phosphorus diffusion, and thermal oxidation. This technique has revealed exact spatial configurations of individual lattice imperfections such as swirl defects, diffusion‐induced dislocations, oxidation‐induced stacking faults, and precipitates.

ISSN:0003-6951    

DOI:10.1063/1.90823

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

A new laser structure, the ’’T‐laser’’, has been monolithically integrated with a MESFET on a semi‐insulating GaAs substrate. Integration is achieved by means of a compatible structure in which the optically active layer of the laser also serves as the electrically active layer of the MESFET. Direct modulation of the laser by means of the transistor is demonstrated.

ISSN:0003-6951    

DOI:10.1063/1.90824

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The effective minority‐carrier lifetime in the active region of Pb0.86Sn0.14Te/PbTe double‐heterostructure (DH) laser diodes has been experimentally determined for a series of diodes with active‐region widths ranging from 0.7 to 3.9 &mgr;m using a measurement technique which involves observing the dependence of the threshold current density on the duration of a current pulse input. From the data, it is inferred that the interface recombination velocity at the heterojunctions is as high as 1×105cm/sec at 5 °K, while the bulk minority‐carrier lifetime is 4.3 nsec. For a typical double‐heterostructure laser with a 2‐&mgr;m active‐region width, this implies a reduction in the internal quantum efficiency due to interface recombination of as much as 80%.

ISSN:0003-6951    

DOI:10.1063/1.90825

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

This paper reports the first measurement of optical‐absorption loss in LiNbO3waveguides and bulk material. This is also the first demonstration of calorimetry as a feasible technique for measuring waveguide absorption in integrated optics. Results indicate that in LiNbO3out‐diffused waveguides the absorption is two orders of magnitude lower than the total loss, implying that the predominant loss mechanism is scattering. The ultimate sensitivity limit for calorimetric determination of absorption losses appears to be ∼10−4dB/cm for optimized geometries.

ISSN:0003-6951    

DOI:10.1063/1.90826

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Room‐temperature cw lasing at 1.063 &mgr;m was obtained in Nd(Al,Cr)3(BO3)4crystals. Cross pumping via Cr3+is as efficient as direct pumping via Nd3+. Thresholds around 20 mW and slope efficiencies up to 13% have been measured. The internal losses were high, around 15%, which we ascribed to imperfect crystal quality. Improvement of crystal quality should lead to thresholds in the mW range.

ISSN:0003-6951    

DOI:10.1063/1.90827

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

The compound 2,2‐dichloro‐1,1,1‐trifluoroethane, CF3CHCl2, has been selected in an exhaustive search as the most promising working material for potentially viable laser separation of deuterium. Highly isotopically selective absorption in CF3CDCl2occurs near 10.2 and 10.6 &mgr;m, accessible with the normal CO2laser. The single‐step deuterium isotopic enrichment factor attains a value of 1400 at a fluence of 10 J/cm2for the dominant photoproduct, trifluoroethene (CF2=CFD and CF2=CFH). The probability for CF3CDCl2dissociation into CF2=CFD photoproduct occurs with a fluence threshold near 1.5 J/cm2and appears to saturate near 100% yield above 15 J/cm2. Liquid‐phase base‐catalyzed H/D exchange occurs rapidly with water without hydrolysis to permit redeuteration of the CF3CHCl2working material.

ISSN:0003-6951    

DOI:10.1063/1.90819

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

An expression is derived for the current dependence of spontaneous emission in the lasing state. It shows that the slope of the emission above threshold is controlled by a product of two terms, of which only one is affected by the dynamics of lasing. Since the other depends on subthreshold properties, the slope of the spontaneous characteristic is not a definitive test of laser models. While a rise in spontaneous emission above threshold is inconsistent with the linear rate equations describing the stimulated recombination, a strong saturation is not supportive of them. As an example, comparison of the properties of the laser of Paoli and Barnes, which exhibited a strong saturation, with data on other stripe units with various degrees of saturation shows that the unusually strong saturation they find is caused by an unusually low product of threshold current and external efficiency, not by a different form of the rate equation. As an aside it is shown that the slope ratio also measures the ratio of junction resistances above and below threshold.

ISSN:0003-6951    

DOI:10.1063/1.90820

出版商:AIP    

年代:1979

数据来源: AIP

摘要:

Al‐coated glasses of molar composition 20Na2O‐10CaO‐70SiO2have been bombarded with a rastered beam of either 7‐ or 10‐keV electrons. SIMS analysis of these glasses indicates a near‐surface layer deficient in Na, bounded by a steep rise of the Na signal. The thickness of this layer increases with electron‐bombardment time until it becomes close to the expected maximum range of electron penetration. No Ca displacement was observed. Below the Na‐deficient layer, a layer containing uncombined Na was found.

ISSN:0003-6951    

DOI:10.1063/1.90828

出版商:AIP    

年代:1979

数据来源: AIP