摘要:

We have studied changes in the absorption, temperature, ultraviolet (UV) spectrum, birefringence, and surface profile of various high‐purity ‘‘UV‐grade’’ fused silica samples during KrF excimer laser irradiation at 400 mJ/cm2and 300 Hz and up to a total of 60 million pulses. All samples exhibit permanent and irreversible changes in the spectroscopic and physical properties. Some samples show a partial ‘‘self‐annealing’’ behavior during the irradiation in which the absorption first increases to a peak value of ∼10%/cm, and then decreases and levels off at a lower value. This may indicate the formation of a new stable state. The radiation‐induced effects are significantly affected by the laser repetition rate, annealing, and ambient temperature of the sample. For comparison, crystalline quartz is tested under similar conditions, and is found to be essentially unchanged by the radiation.

ISSN:0003-6951    

DOI:10.1063/1.104583

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

We demonstrate the generation of optical sidebands with a frequency separation of 170 GHz by nonlinear optical intracavity interaction of light from a 1.3 &mgr;m distributed feedback laser with the population pulsations caused by the longitudinal mode beating of a broad‐area laser and demonstrate a cavity‐enhanced response by approximately 45 dB.

ISSN:0003-6951    

DOI:10.1063/1.104584

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The facet temperature and output power of uncoated AlGaAs single quantum well lasers operated at constant current were measured as a function of time until catastrophical breakdown. The temperature rise is observed to consist of two regimes−an initial linear temperature rise accompanied by a gradual power degradation followed by a rapid nonlinear temperature rise at what appears to be a critical temperature leading to catastrophical optical damage (COD). The time to COD and the pre‐COD facet temperature rise rate are found to have a strong dependence on the diode output power. This facet temperature behavior plus the data obtained from an argon laser probe beam induced heating experiment provide valuable information regarding the mechanisms leading to COD.

ISSN:0003-6951    

DOI:10.1063/1.104585

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The infrared transmission spectra of KTiOPO4(KTP) have been closely inspected in the region between 4000 and 1000 cm−1(2.5–10 &mgr;m) using single‐crystal samples of various thicknesses. The spectral information obtained reveals that the band edge at 4.5 &mgr;m is due to the first overtone of the &ngr;3tetrahedral phosphate fundamental vibration. A heretofore questionable absorption centered at 3.3 &mgr;m has been shown to be the second overtone of this same fundamental vibration.

ISSN:0003-6951    

DOI:10.1063/1.104586

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Optical waveguiding in a crystalline organic semiconductor, namely, 3,4,9,10 perylenetetracarboxylic dianhydride (PTCDA), has been demonstrated in slab and rib waveguides using both end‐fire and grating coupling at &lgr; 1.064 &mgr;m. The effective indices of the transverse electric (TE) modes measured by means of grating coupling are in good agreement with theoretical prediction. A very low propagation loss of 2.5 dB/cm in a PTCDA rib waveguide has been determined from measurements of the scattered light intensity from the top surface of the guide.

ISSN:0003-6951    

DOI:10.1063/1.104587

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The performance of a pulsed laser system consisting of an electron beam pumped XeF(C→A) amplifier injection‐controlled by a wavelength‐agile dye laser is reported. Random sequence tuning over a 27 nm spectral region, centered at 478.5 nm, was demonstrated at a 1 Hz pulse repetition frequency. Laser output energies of 0.8 J with pulse durations of 10 ns were measured.

ISSN:0003-6951    

DOI:10.1063/1.104588

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Current biased samples are illuminated by short pulses of laser light and voltages are measured for a range of temperature 7 K<T<350 K. Classically, no response is expected for times greater than 10 ps after the pulse arrival. However, transient signals with temperature‐independent decay times are observed in Ni and Nb samples, and a similar signal with diminished amplitude is observed in a Au sample.

ISSN:0003-6951    

DOI:10.1063/1.104589

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

The quantitative determination of atomic hydrogen concentrationscHin the vicinity of hot filaments is performed with two‐photon laser‐induced fluorescence. The measurements yield atomic hydrogen concentration profiles up to 28 mm from the filament surface with a spatial resolution of about 0.5 mm. The nonequilibrium nature of the hydrogen dissociation on the filament surface results in a saturation of hydrogen concentration profilescH(r) for gas pressures above 10 mbar. Atomic concentrations in immediate vicinity of the filament are significantly lower than expected from thermodynamical calculations and depend on the filament diameter. Addition of methane results in a decrease ofcHby more than 30% near the filament and a steepercH(r) dependence, demonstrating the accelerated consumption of H atoms by the presence of hydrocarbon species. H concentration profiles for Ta, Ir, and W filaments show a dependence on filament materials which might be taken into account when selecting filament materials for chemical vapor deposition of diamond.

ISSN:0003-6951    

DOI:10.1063/1.104590

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

A study of current quenching in the pseudospark is presented. Current quenching during the conductive phase limits peak conduction current in certain thyratron switches. The quenching phenomenon also occurs in the pseudospark. However, a remarkable feature is that current quenching is observed only below currents of ≊ 2–3 kA, near the onset of superemissive behavior, and thus in the pseudospark is not an upper limit to high current operation. A mechanism involving an instability caused by ion depletion at the plasma boundary is discussed.

ISSN:0003-6951    

DOI:10.1063/1.104591

出版商:AIP    

年代:1991

数据来源: AIP

摘要:

Ion beam sputtering was used to deposit tantalum oxide films on silicon substrates at different positions surrounding a Ta2O5target. dc conductance of the films shows dependence on the ejection angle of sputtered particles and primary ion energy. Capacitance‐voltage characteristics also vary by changing the primary ion energy. These variations of electrical properties are discussed by considering the effect of anisotropic ejection of the sputtered energetic particles.

ISSN:0003-6951    

DOI:10.1063/1.104592

出版商:AIP    

年代:1991

数据来源: AIP