摘要:

The irradiation at 514.5 nm of a ferroelectric liquid crystal (FLC) film doped with a photochromic chiral thioindigo dye causes a change in the birefringence of the FLC film under a constant dc voltage. This birefringence photomodulation is used to create electric field controlled dynamic holograms. The diffraction efficiency of the hologram is found to depend resonantly on the applied dc voltage. The unwinding of the FLC helical structure into a planar alignment as a result of a photoinduced increase of the spontaneous polarization(Ps)and of the corresponding dielectric torque is thought to be at the origin of the observed birefringence photomodulation. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121794

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We demonstrate that combined lateral-vertical oxidation of AlGaAs can be used to change the resonant wavelength of an optical cavity after the single epitaxial growth. A multiple-wavelength array of vertical-cavity surface-emitting lasers with a 48 nm wavelength span has been realized using this technique. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121795

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

By comparing theoretical prediction with experimental performance, we gain insight into the physical operation of lateral current injection lasers. By studying the temperature dependence of lasing stimulated efficiency, we demonstrate the influence of lateral heterobarriers (achieved in this experiment by quantum well intermixing) on the confinement of carriers to the active region. By comparing the evolution of threshold current with temperature for devices of differing contact separations with a self-consistent model of lateral current injection laser operation, we reveal the importance of the interplay between the lateral material gain profile and the optical mode. Understanding these mechanisms, unique to the lateral injection family of lasers, is key to realizing the tremendous potential of this class of lasers to enable optoelectronic integration and novel functional devices. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121796

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Composite glasses containing different metal nanoclusters were obtained by implanting copper, nickel, or copper+nickel ions inSiO2glass. The nonlinear refractive index of the composites was determined by theZ-scan method at a wavelength of 770 nm and with a laser pulse duration of 130 fs. Values ofn2up to0.68 cm2 gW−1were measured in the case of theCu+Niimplanted sample. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121797

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Using an optical tweezer, we trap a DNA polymer tethered bead. Collinear with the tweezer, a red laser light beam probes the bead fluctuations through backscattered radiation measurement. Those fluctuations give information on the flexibility of DNA and can be used to probe the interaction of proteins with DNA. We use this approach to directly monitor the extension of a single DNA polymer beyond its contour length induced by the polymerization of Rec A protein on DNA. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121798

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

This letter describes the fabrication of structured polymer light-emitting devices (LEDs) that produce patterns of light with feature sizes as small as ∼0.8 &mgr;m. Solvent-assisted micromolding of a film of a precursor to poly(p-phenylene vinylene) (PPV), produces variations in its thickness that replicate the relief on the mold. Thermal conversion of this precursor produces a film of PPV with the same surface relief. LEDs formed with the structured PPV emit preferentially in the thin regions of the film. Devices fabricated in this manner may be important for constructing plastic visual displays, and could eventually lead to new subwavelength sources of light suitable for applications in near field optics. ©1998 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.121799

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Carrier dynamics in absorption saturation in an InP/InGaAs nonlinear Bragg reflector is studied by transient reflectance measurements. An ultrafast process of the relaxation time shorter than 100 fs is observed and identified as carrier-carrier scattering. Such an ultrafast process is not observed in the transient reflectance of bulk InGaAs measured with the same photoexcitation level. The difference between these transient reflectance characteristics indicates an enhancement of carrier-carrier scattering in the nonlinear Bragg reflector. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121814

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We analyze the physics of three-level and four-level systems for optically pumped far-infrared quantum well lasers. The higher complexity of the four-level system offers a great advantage because it gives more flexibility to design the dipole matrix elements and phonon scattering rates to enhanceboththe gain and emission efficiency. We propose a four-level scheme that is superior in gain and emission efficiency by an order of magnitude over previous designs. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121815

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Pb(Zr,Ti)O3(PZT) thin-film optical waveguides were grown on Nb-dopedSrTiO3substrates by solid-phase epitaxy to fabricate an electrode/waveguide/conductor structure. The propagation loss was relatively large for a PZT waveguide on a lightly Nb-dopedSrTiO3as compared with the propagation loss of 4 dB/cm for the structure using undopedSrTiO3.An electro-optic beam deflection device was fabricated by preparing a prism electrode on the surface of the PZT waveguide on a lightly Nb-dopedSrTiO3substrate. Efficient deflection of the coupled laser beam in the PZT waveguide as large as 11 mrad was observed by applying 35 V between the prism electrode and the substrate. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121816

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A model of the electrical sheath between plasma and a positively biased wall has been developed for the case of the magnetic field perfectly parallel to the wall. The magnetized sheath and relatively large positive wall potential with respect to the plasma are considered, so that only electron current is present in the sheath. We show that the sheath thickness increases linearly with duct current density. There is good quantitative agreement between the calculated and experimental current–voltage duct characteristics. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121817

出版商:AIP    

年代:1998

数据来源: AIP