摘要:

We report the first demonstration of an InGaAs/InP multiple quantum well Fabry–Perot e´talon modulator. The obtainedon‐offcontrast is 5:1 at −16 V applied voltage for 1540 nm wavelength light. The absorption coefficient of the multiple quantum well around 1540 nm increases from 1000 to 6300 cm−1as the applied voltage increases from 0 to −16 V, and the relative refractive index change is up to −0.9%.

ISSN:0003-6951    

DOI:10.1063/1.102175

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The diffraction efficiency suppression and peak shifting from the Freedericksz threshold voltage are predicted for degenerate four‐wave mixing process in a low‐frequency ac voltage‐biased homeotropically aligned nematic liquid crystal film. The crucial factor is the twist deformation in the induced phase grating. Significant amounts of diffraction efficiency suppression and peak shift are shown both in numerical and experimental results.

ISSN:0003-6951    

DOI:10.1063/1.102176

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We show that two‐photon absorption can lead to serious deterioration in the all‐optical switching characteristics of nonlinear directional couplers and distributed feedback gratings.

ISSN:0003-6951    

DOI:10.1063/1.102177

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We describe for the first time the theory of frequency modulation (FM) response in distributed feedback (DFB) lasers with two active segments. FM response is enhanced due to two‐segment operation; the enhancement decreases at higher modulation frequencies and higher photon densities. Bandwidth of the response can extend to the multigigahertz range. The FM response is dramatically different in lasers operating in the red‐ and blue‐shifted static tuning regimes. We find good agreement between the theory and our measurements of multigigahertz FM response of two‐segment DFB lasers.

ISSN:0003-6951    

DOI:10.1063/1.102178

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

Nonlinear optical transmission and switching phenomena have been observed in directional coupler devices fabricated from soluble polydiacetylenes. Effects due to both slow thermal nonlinearities and ultrafast (picosecond) electronic nonlinearities were identified. At the operating wavelength of 1.06 &mgr;m used here, the ultrafast electronic nonlinear phenomena originated from intensity‐dependent changes in the imaginary part of the refractive index due to two‐photon absorption effects.

ISSN:0003-6951    

DOI:10.1063/1.102179

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The carrier‐induced optical frequency deviation undergoes an unusual phase reversal in external‐cavity semiconductor lasers when the modulation frequency is equal to that of the external‐cavity mode spacing. A model based on the coherent nature of the external optical feedback is used to explain this phenomenon.

ISSN:0003-6951    

DOI:10.1063/1.102180

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

A high‐resolution scanning phase‐measuring acoustic microscope (SPAM) has been developed and used to image the near‐surface residual stress field around features etched in sputtered alumina via the acoustoelastic effect. This microscope operates at 670 MHz and has a resolution of 5–10 &mgr;m, depending upon the amount of defocus. Relative velocity changes of sample surface waves as small as 50 ppm are resolved. Images of the stress field at the tip of a 400‐&mgr;m‐wide slot etched in alumina are presented and compared with a finite element simulation. The SPAM uses an unconventional acoustic lens with an anisotropic illumination pattern which can measure anisotropic effects and map residual stress fields with several &mgr;m resolution and a stress sensitivity of 1/3 MPa in an alumina film.

ISSN:0003-6951    

DOI:10.1063/1.102326

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

MeV ion implantation in Si above a dose of 1014/cm2leads to secondary defect formation in a buried layer, which is rather stable. Annealing of Si(100) implanted with 2.0 MeV B+ions to a dose of 2.2×1014/cm2has been investigated by means of cross‐sectional transmission electron microscopy. After annealing at 900 °C for 15 min, dislocation loops elongated along [110] were found. A remarkable decrease in secondary defect formation has been observed if, in addition, 140 keV Si+was implanted prior to annealing.

ISSN:0003-6951    

DOI:10.1063/1.102181

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

The transmission through thin gold films on optical quartz during laser blow‐off with 15 ns, 532 nm laser pulses has been measured. Dramatic changes in transmission mark the duration of the blow‐off event with laser fluences above the threshold for removal. The integrated laser fluence required to blow‐off the films is roughly independent of incident laser fluence, and is close to that expected to raise the temperature of the film to the boiling point at the film‐support interface.

ISSN:0003-6951    

DOI:10.1063/1.102182

出版商:AIP    

年代:1989

数据来源: AIP

摘要:

We present a description of electrorheological fluids in terms of an electric field induced phase transition at a critical electric fieldEc. Theoretically, we find that as the applied field exceedsEc, the osmotic pressure becomes negative and the liquid experiences a phase transition to a solid phase.Ecis experimentally determined as a function of concentration in one system. Our theoretically predicted phase diagram is in reasonable agreement with our experimental data.

ISSN:0003-6951    

DOI:10.1063/1.102183

出版商:AIP    

年代:1989

数据来源: AIP