摘要:

Three‐dimensional thermal diffusion effects are shown to be important for photothermal imaging. Signal enhancement near thermal boundaries is observed. The effects are applied to locating defects in a crystalline ceramic. A general application to signal enhancement in powders over bulk solids is suggested.

ISSN:0003-6951    

DOI:10.1063/1.92800

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The magnitude of the intrinsic resonant frequency exhibited by a semiconductor laser operating at a fixed level above threshold is shown to be determined by the product of the photon lifetime for the unpumped laser cavity and the differential lifetime of the carriers at threshold. This conclusion differs from the generally accepted view that the relevant lifetimes for the resonant frequency are the carrier and photon lifetimes evaluated at threshold and resolves the existing discrepancy between measured and calculated values. The present analysis is used to evaluate the shift in the resonant frequency produced in a typical proton‐bombarded stripe‐geometry laser by variations in the laser’s cavity loss.

ISSN:0003-6951    

DOI:10.1063/1.92801

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

We report the observation of bursts of transform‐limited 0.65‐psec pulses at 1‐GHz repetition rates by passive mode locking of a buried optical guide laser in an external cavity. The lasers contain a saturable absorber at the exit facet, specifically introduced by 600‐keV proton bombardment at a 3×1015‐ cm−2dosage level.

ISSN:0003-6951    

DOI:10.1063/1.92802

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A population inversion of the (001)–(100) transition in CO2gas has been observed when the cold CO2or CO2, and He gases were vertically injected into a high‐temperature, thermally equilibrated, low‐subsonic N2flow in a duct having a constant area. Simultaneously, the formation of a gas throat was observed. A small signal gain of 0.95/m was measured at 2 mm downstream from a gas injecting point.

ISSN:0003-6951    

DOI:10.1063/1.92803

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Measurements have been made of the phase noise of six different types of single‐mode diode laser in an unbalanced Michelson interferometer, as a function of optical path difference. The frequency dependence of the phase noise has also been determined. Possible origins of the frequency fluctuations which result in the phase noise are discussed. The detrimental effect of the phase noise on the sensitivity and dynamic range of optical fiber interferometer sensors is briefly discussed.

ISSN:0003-6951    

DOI:10.1063/1.92804

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

A new optical information storage technique is described which operates by irreversibly altering the absorption properties of a microscopically textured surface. Reflectance changes of greater than a factor of 100 have been obtained by local melting of the surface. A random array of Si columns with cross‐sectional dimensions less than 100 nm, formed on a Si film by reactive ion etching, has a visible reflectance of less than 0.01. By irradiation with a focused laser beam, at a power density of ≲8 mW/&mgr;m2, the columns melt to form a surface with a specular reflectance of ∼0.4. The applicability of this surface structure as a permanent optical storage medium is discussed. In general, this surface texturing can be applied to a wide variety of materials with the advantages of increased sensitivity to the writing beam, large contrast between the written and unwritten areas and reduced lateral energy flow.

ISSN:0003-6951    

DOI:10.1063/1.92805

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

Direct nuclear pumping of a3He‐Xe laser, lasing at 2.63 &mgr;m, has been achieved. Scaling of the laser output with xenon concentration, total pressure, and thermal neutron flux has been investigated. A peak power in excess of 200 W was obtained at a total pressure of 3 atm, a gas mixture consisting of 5 % xenon and 95%3He, and a peak thermal flux of 6×1016n/cm2 s.

ISSN:0003-6951    

DOI:10.1063/1.92806

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

We report the first pulsed opto‐acoustic spectroscopy of low loss condensed media in the infrared region. Stimulated Raman scattering in high‐pressure hydrogen gas was used for down shifting pulsed tunable dye laser radiation through first‐ and second‐order Stokes processes. Measurements of the absorption spectra of liquid ethylene in the region of 0.7–1.6 &mgr;m indicate the general applicability of this technique to other important problems.

ISSN:0003-6951    

DOI:10.1063/1.92807

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

The observation of a surface acoustic wave parametric oscillation in Si‐on‐LiNbO3is reported. The threshold power required for parametric oscillation was substantially reduced by the highly efficient surface acoustic wave reflectors. Experimental frequency was 130 MHz, and the conversion efficiency from the pumping to the surface acoustic waves was about −21 dB.

ISSN:0003-6951    

DOI:10.1063/1.92786

出版商:AIP    

年代:1981

数据来源: AIP

摘要:

We show that a cold, dense laboratory plasma can be readily characterized by extreme ultraviolet absorption spectroscopy. The plasma is produced by irradiating a thin aluminum foil with a pulsed soft x‐ray source. The same source also provides a backlighting continuum for absorption spectroscopy. Time‐integratedL‐shell spectra obtained with a grazing incidence spectrograph show collisionally broadened absorption lines of A1 IV and A1 V. The spectra provide plasma temperature and electron density measurements of ≳12 eV and 0.6×1021cm−3, respectively.

ISSN:0003-6951    

DOI:10.1063/1.92787

出版商:AIP    

年代:1981

数据来源: AIP