摘要:

We demonstrate a design that allows fabrication of substrate input/output resonant-cavity photodetectors and vertical cavity lasers (VCLs) on the same substrate without regrowth. By selectively oxidizing a few layers in the bottom mirror the as-grown 80&percent; reflectivity mirror, used as the input mirror for the detector, is converted to a 99.3&percent; reflectivity mirror allowing fabrication of VCLs from the same epitaxial material. Since these two reflectivities are uncorrelated, the detectors and VCLs can be individually designed. Despite the change in refractive index from ∼3 to ∼1.6 in the oxidized layers, the structure can be designed to have nearly the same resonance wavelength for both the detectors and VCLs. Using this design strategy, we have successfully fabricated high-performance resonant photodetectors and VCLs from the same epitaxial material. The photodetectors have an absorption of 56&percent; and an optical bandwidth of 5.9 nm, in good agreement with theory. Small diameter, single-mode VCLs have threshold currents as low as 180 &mgr;A with 33&percent; slope efficiencies while multimode devices have slope efficiencies exceeding 60&percent; with less than 500 &mgr;A threshold currents. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122951

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Recently, chromophores with a large figure-of-merit for incorporation into photorefractive polymers with low glass-transition temperature have become available. However, their rather polar nature so far limited their use in typical nonpolar photoconducting matrices due to dye aggregation. By incorporation of an additional polar compound we were able to influence this situation favorably. The material we report here has a factor 4 to 5 (2) improved index modulation amplitude (gain coefficient) compared to the best previously known materials. The material is sufficiently resistant against phase separation and operates in the near infrared at typical wavelengths of commercially available high-power laser diodes. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122950

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Confocal microscopy of single molecules bound on a silica surface is performed with precompressed 27 fs laser pulses. Interferometric autocorrelation using a single molecule is demonstrated. It is also shown that orientational distributions can be directly obtained from one- and two-photon images produced with circularly polarized light. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121730

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Femtosecond dynamics of color changes due to photoinduced electron transfer and reverse reactions in polymeric 4,4′-bipyridinium di-iodides salts were studied with a fs laser pump–probe technique. The characteristic color change was shown to take place in less than 1 ps by fs-laser excitation of an ion-pair charge-transfer band, which may be applied to ultrafast THz all-optical switching devices using visible light. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.122952

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We propose a method of heterodyne detection of far-infrared signals using quantum interference between one- and two-photon absorption. We suggest different implementations of the scheme using multiple quantum well detectors and evaluate its sensitivity. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121707

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report the observation of steady-state two-dimensional photorefractive self-trapping and screening spatial soliton formation in a sample of potassium–lithium–tantalate–niobate in the centrosymmetric paraelectric phase. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121708

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The authors present a way to monolithically integrate surface—and substrate—emitting vertical cavity surface emitting lasers (VCSELs) on a single substrate for use in smart pixel applications. Spatially selective oxidation is used to adjust the reflectivity of distributed Bragg reflectors to fabricate surface and substrate emitting VCSELs with threshold currents of 65–70 &mgr;A, far field FWHMs of 9°–16°, and slope efficiencies of 16&percent;–18&percent;. Threshold currents and far field angles for various aperture dimensions are measured and discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121709

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A study of thermo-optical coefficient(dn/dT)of GaN using spectroscopic ellipsometry is made, and a large thermo-optical nonlinearity near band edge, which increases with increasing temperature, has been observed. Kramers–Kronig transformation has been used to verify our results and a qualitative consistency has been obtained. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121710

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report investigations of a space-time structure of the electric field of laser plasma from a solid target. An ArF excimer laser with an intensity ofI≅108 W/cm2was used to produce the plasma on various targets placed in air at atmospheric pressure. A strong difference in both the amplitude (by more than 1–2 orders of magnitude) and the structure of the electric field for conductive and dielectric targets has been observed. The field distribution for a conductive target was found to correspond to a dipole configuration of charges in the laser plasma, while for the dielectric target a quadrupole configuration was revealed. Possible explanations and applications of the observed effect are discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121711

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Homoepitaxially grown nitrogen-doped ZnTe layers have been exposed to a hydrogen (deuterium) plasma. After hydrogen (deuterium) diffusion, an infrared absorption band appears at 3346cm−1(2489cm−1).It is assigned to the vibrational stretching mode of the N–H (N–D) bond. It is also shown that the absence of such detectable bands in heteroepitaxially grown ZnTe/CdZnTe layers can be explained by thermal strains originating from the difference between the ZnTe and the CdZnTe thermal expansion coefficients. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121712

出版商:AIP    

年代:1998

数据来源: AIP