摘要:

Lasing action at 1.73, 1.23, and 0.85 &mgr;m was obtained by a threefold upconversion process in Er:YLF at 110 K using a 1.53 &mgr;m Er:glass pump laser. The 1.73 &mgr;m transition had the lowest threshold and highest pump conversion efficiency.

ISSN:0003-6951    

DOI:10.1063/1.100842

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Photocarrier generation and injection processes in double‐layered organic photoconductors consisting of carrier generation layer (CGL) and carrier transport layer (CTL) were studied by means of photoacoustic and xerographic time‐of‐flight methods. In the photoacoustic method, the photocarrier generation efficiency in the CGL was derived by measuring the decrease in photoacoustic signal due to carrier recombination in the CGL. On the other hand, in the xerographic method, the ratio of the number of holes emitted into the CTL to that of absorbed photons in the CGL was obtained from the temporal change in surface voltage under light pulse irradiation. From comparing two experimental results, we evaluated the injection efficiency of holes at the CGL/CTL interface. The injection efficiency is determined by the trapping of holes at the CGL/CTL interface.

ISSN:0003-6951    

DOI:10.1063/1.100794

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A neodymium‐doped single‐mode fiber emits light at 496 and 633 nm, as well as at several near‐infrared wavelengths, when pumped by a mode‐locked,Q‐switched Nd:YAG laser operating at 1064 nm. A threshold peak pumping power of approximately 50 kW is required for the process; peak emitted powers of several watts were observed. The blue line is more than 15 nm wide at high pumping levels and possesses large temporal pulse dispersion across its spectrum. Amplified spontaneous emission via a three‐photon pumping process is proposed to account for the phenomenon.

ISSN:0003-6951    

DOI:10.1063/1.100795

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A new method is proposed to generate transversely coherent energetic photon beams. It does not rely on stimulated photon emission, therefore, is not subject to the same technological and cost limitations which affect bound‐state x‐ray lasers and free‐electron x‐ray lasers. The method leaves unchanged the photon source; it increases transverse coherence by dynamical optical means, i.e., using nonstationary optical elements. It is well suited to first‐order interference experiments (e.g., x‐ray holography) particularly with synchrotron radiation sources.

ISSN:0003-6951    

DOI:10.1063/1.100796

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A new laser‐assisted crystal growth technique that enables three‐dimensional patterning of the GaAs quantum well (QW) active layer within a laser diode structure is demonstrated. In this technique, the GaAs QW is locally heated with superimposed Ar+and Nd:YAG laser beams during a pause in the metalorganic chemical vapor deposition growth. The evaporation rate of the GaAs is greatly increased by the laser heating, locally thinning the QW. After exposure, the crystal growth is resumed, burying the patterned QW within the crystal. Transmission electron microscopy is used to quantify the lateral profile of the QW thickness while photoluminescence is used to demonstrate the spatial variation of the energy band gap. Finally, multiple wavelength operation of broad‐area diode lasers is observed, consistent with the spatial variation in the energy band gap.

ISSN:0003-6951    

DOI:10.1063/1.100797

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The dynamic properties of GaAs/AlGaAs graded index separate confinement heterostructure single quantum well lasers have been investigated. The sublinear gain‐carrier density relation imposes bandwidth limitations on these lasers. However, a considerable increase in the resonance frequency (∼55% for a quantum well width of 140 A˚) was observed for lasers with cavities shorter than a certain cavity length. This discontinuous increase in bandwidth with decreasing cavity length coincides with the transition from first to second quantized state lasing and the associated recovery of the differential gain.

ISSN:0003-6951    

DOI:10.1063/1.100798

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Rate equations are proposed which describe the operation of a crystal as a resonant cavity for x rays. The formalism, which applies equally well to two‐beam or multibeam diffraction cases, is not restricted to any particular mechanism of x‐ray emission. It automatically takes into account dynamical diffraction effects on energy flow (group velocity) and absorption (the Borrmann effect) which are shown to be instrumental in increasing gain and lowering the lasing threshold. The resonant x‐ray modes are those for which the group velocity vanishes (the resonant diffraction condition).

ISSN:0003-6951    

DOI:10.1063/1.100799

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A novel material deposited by molecular beam epitaxy at low substrate temperatures using Ga and As4beam fluxes has been used as the active layer for a high‐speed photoconductive optoelectronic switch. The high‐speed photoconductive performance of the material was assessed by fabricating two devices: an Auston switch and a photoconductive‐gap switch with a coplanar transmission line. In a coplanar transmission line configuration, the speed of response is 1.6 ps (full width at half maximum) and the response is 10 to 100 times greater than that of conventional photoconductive switches. Since the material is compatible with GaAs discrete device and integrated circuit technologies, this photoconductive switch may find extensive applications for high‐speed device and circuit testing.

ISSN:0003-6951    

DOI:10.1063/1.100800

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Single‐beam overwriting with melt‐erasing process was made in a 5.25‐in.‐diam phase‐change optical disk using an In22Sb37Te41recording film. In the overwriting between 2 and 3 MHz signals at the linear velocity of 3–11 m/s, a carrier to noise ratio (C/N) more than 46 dB and an erasability less than −35 dB could be obtained. This high erasability was found to be due to the melt‐erasing process. This disk presents highly erasable overwriting and long data retention time supported by an activation energy of 2.3 eV and a temperature of 230 °C for crystallization of the amorphized part.

ISSN:0003-6951    

DOI:10.1063/1.101417

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The first experimental observation of strong optical nonlinearities induced by a laser field in polymer dispersed liquid crystals is reported. The measured rise time of the effect agrees with the interpretation of a thermal origin of the phenomenon.

ISSN:0003-6951    

DOI:10.1063/1.100801

出版商:AIP    

年代:1989

数据来源: AIP