摘要:

Free‐space electro‐optic sampling is an alternative method for the characterization of freely propagating terahertz beams with subpicosecond temporal resolution. In contrast to resonant photoconductive dipole antennas, free‐space electro‐optic sampling via the linear electro‐optic effect (Pockels effect) offers a flat frequency response over an ultrawide bandwidth and the potential for a simple cross‐correlation signal of the terahertz and optical pulses. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114909

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Microcavity lasers with differing mirror designs are used to study the influence of the index contrast ratio on the mode size and temporal response. The experimental results demonstrate the advantages of high contrast Bragg reflectors for reducing the mode area while simultaneously increasing the laser temporal response. We suggest that the far‐field angle is preferable to an effective cavity length as a characterization parameter, since the far‐field angle is directly measurable and yields the photon lifetime. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114910

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The growth rate of fiber Bragg gratings written using 193 nm light from an ArF excimer laser is linearly proportional to the laser pulse energy density for fibers with high germanium doping but proportional to the square of the pulse energy density for standard telecommunications fibers with low germanium concentration. The two‐photon process in standard fibers yields refractive index increases that saturate around 10−3, an order of magnitude improvement over previous results in this type of fiber without sensitization treatment. The two types of photoinduced refractive index gratings have comparable thermal stability and preserve about 50% of their initial magnitude after 30 min at 600 °C. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114911

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report the results of an all-optical programmableANDlogic gate. This gate consists of a germanium-doped silica planar waveguide, a laser, and the means of coupling two fundamental frequency beams into different guiding modes of the waveguide along with a second harmonic beam coupled into one guiding mode. These waves interfere in the film generating a set of semipermanent second-order susceptibility gratings which give rise to the waveguide, the film-generated second harmonic light wave made to behave as an output of a logicANDgate. The fundamental and second harmonic light were sent into the waveguide during the programming sequence, but only the fundamental light was injected to probe the logic gate to produce an output. The measured signal-to-noise ratio was 17 dB.©American Institute of Physics

ISSN:0003-6951    

DOI:10.1063/1.115564

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A critical assessment of thermal models for laser sputtering at high fluences is presented. It is argued that the model explaining such sputtering by involving a subsurface superheating effect misinterprets the meaning of ‘‘vaporization’’ and ‘‘boiling’’. As a result inappropriate boundary conditions are used, including those for both the surface temperature and for the surface temperature gradient. On the contrary, it is shown that explosive boiling (also termed phase explosion) in the sense pioneered by Martynyuk and by Fucke and Seydel remains the only thermal mechanism able to explain laser sputtering at high fluences. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114912

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

With two coherent waves incident to a two‐dimensional (2D) nonlinear optical superlattice containing Kerr form dielectric nonlinearity, the optical bistability related to transition between a forbidden transmission state and an allowed transmission state can occur through the index‐modulation mechanism. This kind of bistability is difficult to obtain in the case of only one incident wave. The power cost for the bistability might be very low. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114913

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The properties of an acoustoelectrically active surface acoustic wave (SAW) propagated on the (112) cut [11¯0] direction of gallium arsenide are studied theoretically. The leaky nature of this SAW (LSAW) which has three displacement components of comparable magnitude is demonstrated. The low attenuation (4.94×10−5dB per wavelength) of the LSAW is obtained. The values of the velocity and the electromechanical coupling coefficient of the LSAW, equal to 3047.4 m/s and 9.3×10−4, respectively, are acquired and agree with the results of experiments carried out previously. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114914

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We have studied the influence of high repetition rates, up to 300 Hz, on four pulsedp‐type germanium lasers. The maximum electric input power which terminates laser action via heating is a characteristic value for each crystal. We show magnetic field sweeps and introduce a diagram which connects the dynamical behavior of light and heavy holes to optical phonons and impurity states. We find that temperature is an essential key for the understanding of the laser action. High repetition rates or continuous wave operation may be achieved with proper design of the crystal and its cooling environment. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114915

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

By measuring the spontaneous emission from strained and unstrained 1.5 &mgr;m InGaAs quantum well lasers as a function of temperature we deduce the temperature dependence of the radiative current density at threshold corresponds to a characteristic temperatureT0≊300 K, close to that expected from theory, whereasT0of the threshold current is around 60 K. We conclude from our analysis that the large temperature dependence of long wavelength lasers is due to Auger recombination. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114916

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report the results of a high efficiency room temperature continuous wave (cw) vertical‐cavity surface‐emitting laser. The structure is obtained by four deep H+implantation using tungsten wires as the mask. The fabrication process is the simplest ever reported in vertical‐cavity surface‐emitting laser fabrication. The largest differential quantum efficiency of 65% and maximum cw light output power over 4 mW have been achieved for the 15×15 &mgr;m2device. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.114917

出版商:AIP    

年代:1995

数据来源: AIP