摘要:

The generation of 15‐ps light pulses at 1.23 and 1.26 &mgr;m having 200 mW peak power at a repetition rate of up to 10 MHz from directly modulated unbiased V‐groove InxGa1−xAsyP1−ylasers is reported. Specially designed avalanche generators are employed for modulation of the laser injection current. The light pulses are analyzed using microstructured Ge photodetectors having a response of 62 ps at full width half‐maximum. A deconvolution technique based on a theoretical analysis of the complete circuit of the detection system is applied to reduce the large error occurring normally when the characteristics of fast pulses are determined from the response of much slower detectors. This technique is proved by independent experiments to hold. A spontaneous lifetime of 1.5 ns of the charge carriers in the active layer of the laser is determined from the measured delay times between the optical and electrical pulses.

ISSN:0003-6951    

DOI:10.1063/1.96942

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Continuous lasing has been observed at 650 nm with a helium‐neon electrical discharge placed in an ultrahigh finesse optical cavity. This new lasing line is attributed to a Stokes–Raman process between the 1s5 and 1s4 electronic states of neon atoms pumped by the 632.8‐nm neon lasing line. A gain calculation based on a near‐resonant stimulated electronic Raman process predicts a lasing threshold for the 650‐nm line near that measured. Lasing output power was measured as a function of discharge current and helium‐neon gas pressure for the pump line and for the Stokes line.

ISSN:0003-6951    

DOI:10.1063/1.96943

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Continuous‐wave (cw) operation at temperature up to 33 °C of an AlGaInP/GaInP mesa stripe laser has been achieved for the first time. The threshold current was 106 mA at 30 °C for a device with a mesa stripe 6 &mgr;m wide and 250 &mgr;m long. The emission wavelength was 678 nm under cw operation at 20 °C. The wafer, which was grown by atmospheric pressure metalorganic chemical vapor deposition, had a dually stacked cladding structure in addition to a conventional double heterostructure. The mesa structure was formed by selective chemical etching of GaAs/AlGaAs over layers. The effect of the mesa structure on threshold current density, thermal resistance, and other characteristics was examined.

ISSN:0003-6951    

DOI:10.1063/1.96944

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

We report the demonstration of a new concept that permits the fabrication of low‐loss Ti:LiNbO3waveguide bends with radii much smaller than previously achieved.

ISSN:0003-6951    

DOI:10.1063/1.96945

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Thin‐film electroluminescent devices employing a new phosphor material ZnS:Sm,P have been found to exhibit bright red emission. Luminous efficiency of ZnS:Sm,P phosphor films is higher than that of ZnS:Sm phosphor films in the range of annealing temperature above 500 °C. A brightness of 1000 cd/m2and an efficiency of 8×10−2lm/W have been obtained in the devices with ZnS:Sm(1 at. %),P(0.5 at. %) phosphor films annealed at 600 °C. These results indicate that P is an efficient co‐activator for Sm in ZnS.

ISSN:0003-6951    

DOI:10.1063/1.96946

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The acceleration sensitivity of acoustic surface wave resonators (and delay lines) on quartz substrates supported uniformly at the base has been calculated. For normal acceleration the calculated sensitivity is almost two orders of magnitude lower than the lowest published measurements. For in‐plane acceleration the calculated sensitivity is comparable to the best published measurements. This causes us to believe that uniform base support has not been realized in practice and, in fact, may be impossible to achieve. For normal acceleration and nonuniform base support the calculations indicate that increasing the thickness of the substrate decreases the acceleration sensitivity. Experimental verification of this is presented. However, for in‐plane acceleration the calculations indicate that increasing the thickness of the substrate increases the acceleration sensitivity.

ISSN:0003-6951    

DOI:10.1063/1.96947

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The ultrasonic waveforms generated by a pulsed laser incident at two positions on a steel plate are studied as a function of laser energy. At the 45° position there is a steady increase in compression wave amplitude with energy when passing from thermoelastic to ablation regimes, in contrast to the epicenter where there is a large increase in amplitude and change of pulse shape. It is concluded that the thermoelastic and ablation sources are comparable in generation efficiency per unit laser energy, except close to the epicenter, and that the chief effect of raising the power density is to vary the angular distribution of ultrasonic energy.

ISSN:0003-6951    

DOI:10.1063/1.96965

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Experimental measurements are presented of space and time integrated x‐ray emission from aluminum plasma produced by 2 ns (full width at half‐maximum), 268 nm Raman compressed KrF laser pulses. A single temperature spectrum was measured giving temperatures of 75–440 eV over the range of intensities 9×1011–2×1013W/cm2. This scaling agrees well with a simple self‐regulating model. Conversion of laser energy into x rays above 1 keV energy was found to scale asI2.37Lreaching 0.35% at 3.5×1013W/cm2.

ISSN:0003-6951    

DOI:10.1063/1.96966

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Optical emission spectroscopy was applied to study the rf glow discharge in hydrocarbons used for the deposition of amorphous hydrogenated carbon (a‐C:H). The optical data in conjunction with mass spectrometric measurements show that the species found in the glow region are very specific for the hydrocarbon used (e.g., benzene), but they are not directly related to the structure of thea‐C:H film deposited. In the vicinity of the negatively self‐biased cathode strong emission from CH is observed, irrespective of which hydrocarbon is used. The excited CH radicals are shown to result from fragmentation of the impacting hydrocarbon molecules. We conclude that this fragmentation upon impact is the key mechanism for the formation of harda‐C:H, irrespective of the type of hydrocarbon used for the deposition.

ISSN:0003-6951    

DOI:10.1063/1.96967

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Linear polydimethylsiloxanes (PDMS’s) are liquid polymers between 200 and 550 K and are well suited for experimental studies in fluid mechanics because (1) they are commercially available in a wide range of molecular lengths, (2) they are transparent and colorless, and (3) their flow behavior can be predicted from their molecular length. A particular PDMS can flow either as a viscous or strain rate softening fluid, depending upon its molecular length and the applied strain rate. Six different flow regimes are defined here to aid the selection of the appropriate PDMS for any particular experiment in fluid dynamics. Diffusion is sufficiently slow in PDMS’s of long molecular length so that finite strains can be visualized by the deformation of strain markers within it. This allows laboratory modeling of three‐dimensional strain histories in fluids which previously could only be approached by two‐dimensional numerical modeling.

ISSN:0003-6951    

DOI:10.1063/1.97008

出版商:AIP    

年代:1986

数据来源: AIP