摘要:

A recently developed near‐field optical technique, the solid immersion lens (SIL), is utilized in a realistic demonstration of near‐field optical data storage. Using 830 nm light, a 360 nm optical spot size is obtained at the exit surface of the SIL and is transferred across a small air gap to the surface of a spinning magneto‐optical disk. Reading and writing of data are achieved at a density of 3.8× 108bits/cm2with a data rate of 3.3×106bits/s. The subwavelength gap between the lens and the disk is maintained at a media velocity of 1.25 m/s by incorporating the lens into an air‐bearing slider. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116127

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

The optical nonlinearity induced by electrical poling decays gradually in poled polymers. This suggests that the molecular alignment can be reoriented in the polymer matrix at room temperature by the external electric field. We measured the frequency responses and the temperature characteristics of second‐harmonic generation (SHG) in a dye doped polymer in order to clarify the electric field dependence of the nonlinearity. The experimental results show that there is a slow response of the SHG coefficient variation due to the reorientation of nonlinear molecules and another fast response. This characteristic can be applied to develop a new type of nonlinear optical devices by dynamically controlling the nonlinearity of the material by the external electric field. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116128

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

A new type of polymer light emitting diodes that emit white light is reported. In these diodes, several electroluminescent substituted polythiophenes have been combined to give the necessary components of the visible spectrum. These emitting polymers are then mixed with an insulating polymer to diminish the energy transfer from high‐band‐gap polymers to low‐band‐gap polymers. The resulting emission at 20 V is shown to be close to the equienergy white point as defined by the CIE (Commission Internationale de l’Eclairage). ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116129

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the demonstration of an electro‐optic sampling technique that allows for the detection of freely propagating terahertz radiation. Coherent sampling is performed in a poled polymer device that is physically separated from the emitter. The poling electrodes in the sampling element are found to have an integrating effect on the incident terahertz field. The shot noise limited minimum detectable field in the polymer is 100 (mV/cm)/&sqrt;Hz. We discuss methods by which the sensitivity may be significantly enhanced. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116130

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Low‐temperature grown surface‐reflection all‐optical switching has been demonstrated with ultrafast photoresponse (1.5 ps), low switching energy (2 pJ), high‐contrast (13 dB), polarization independence, and wide operation wavelength range in the 1.55 &mgr;m band using low‐temperature‐grown Be‐doped strained InGaAs/InAlAs multiple quantum wells. The combination of low‐temperature growth and Be‐doping contributes to the ultrafast photoresponse. Additionally, the introduction of compressive strain and a mirror with 1% reflectivity greatly enhances optical nonlinearities. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116131

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We study the emission dynamics of two In0.2Ga0.8As/GaAs microcavity lasers after femtosecond optical excitation at 20 K. The pulse widths and the peak delays of &lgr; and a 2&lgr; cavity are compared. Pulses as short as 3.3 ps (9.5 ps) and peak delays as short as 8.2 ps (16.5 ps) are obtained with the 2&lgr; cavity (&lgr; cavity). The pulse widths and peak delays are well described by a model based on a rate equation analysis for carrier and photon densities; in particular, the better high speed characteristics of the 2&lgr; cavity compared to the &lgr; cavity are well reproduced. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116132

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

This letter reports a scanning electron microscopy investigation of surface acoustic wave diffraction on the zigzag domain wall in a Gd2(MoO4)3crystal. The zigzag domain wall with ∼80 &mgr;m period was formed in a Gd2(MoO4)3crystal by applying the external mechanical stress. It is shown that the surface acoustic wave diffracts on the zigzag domain wall in a ferroelastic Gd2(MoO4)3crystal. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116133

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Detection of surface and subsurface flaws is achieved using the time reversal process leading to self‐focusing Rayleigh waves. The generation of surface waves is accomplished with an array of transducers coupled to the specimen with a Plexiglas wedge. The advantages of this technique are demonstrated with the detection of surface and subsurface holes of subwavelength dimensions. An optical interferometer is used to control the surface acoustic field obtained with such a time reversal process. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116134

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

An ultrasound transducer with low synthetic quality factor, for in‐air applications, is presented. It is realized by curving a thin sheet of polyvinylidenefluoride and by assembling the so shaped piezo‐polymer film onto a mobile support. The resonance frequency, which is inversely proportional to the bending radius, can be easily varied on a range of some tens of kHz, 30–65 kHz, by mechanically controlling the opening arc angle of the curved film. An ultrasound transducer with both controlled resonance and controlled axial resolution is obtained. The combination of the different resonance frequencies, related to different opening angles, leads to a synthetic broad‐band transducer with unity quality factorQ. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116447

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

It is shown theoretically that the space charge field generated by two‐wave mixing in a photorefractive crystal may have a resonant response when a dc field and a sinusoidal ac field are simultaneously applied. Resonance occurs when the frequency of the ac field is equal to the eigenfrequency of the space charge wave determined by the dc voltage. Analytical expressions are derived for the magnitude of the space charge wave and the optimum ratio of the ac to dc field is determined. The enhancement of the space charge field is shown to be considerably higher than that obtained by a nonresonant method utilizing a sinusoidal ac field alone. Under optimum conditions the maximum space charge field available is equal tomEq/2&sqrt;2, wheremis the modulation of the interference pattern andEqis the saturation field. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.116448

出版商:AIP    

年代:1996

数据来源: AIP