摘要:

Strongly confining waveguides were fabricated in LiTaO3at high temperature (540–610 °C) by short‐time (≤6 s) rapid thermal annealing. Single‐step photolithography is able to accomplish the simultaneous fabrication of a waveguide and a periodically domain‐inverted structure for second‐order quasiphase‐matching blue‐light generation. A measured normalized conversion efficiency of 7%/W cm2for a physical length of 0.55 mm in a planar quasiphase‐matching waveguide showed that this single‐step process can lead to high conversion efficiency in channel waveguides. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117003

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the growth and photoluminescence (300 and 4.2 K) characterization of unintentionally doped GaN on both exact and vicinal (0001) sapphire substrates. The GaN heteroepitaxial layers are grown by metalorganic chemical vapor deposition on sapphire substrates using various growth conditions. The (0001) Al2O3c‐plane substrates are oriented exactly (0001) or misoriented either 2° towards theaplane (112¯0), 5° towards themplane (101¯0), or 9° toward themplane. A comparison of the 300 and 4.2 K optical characteristics of the samples grown on the different substrates indicates that a higher photoluminescence intensity is measured for the films on misoriented substrates. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117004

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Photoassisted poling of azobenzene containing polymer films at room temperature using polarized Ar+laser beam as pump light was studied. Irradiating the films withp‐polarized pump light at an incident angle to the normal during the poling process, second harmonic generation with in‐plane anisotropy could be induced. Second order nonlinear optical coefficient,d33, of the poled sample was measured to be 20 pm/V. The second harmonic generation properties induced by photoassisted poling and thermal assisted poling were compared. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117005

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Resonant slot and dipole antennas coupled to low‐temperature‐grown GaAs photomixers have been fabricated and tested at terahertz operating frequencies. Enhanced output power is seen from the resonant structures compared to mixers coupled to broadband self‐complementary spiral antennas. Driving point impedances as high as 300 &OHgr; are attained at the resonant frequencies. These devices will be useful as fixed frequency local oscillators for submillimeter heterodyne receivers. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117006

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We demonstrate a technique to modify the strain in a planar vertical‐cavity semiconductor laser. The technique consists of locally melting a hole in the wafer next to the device by means of a focused laser beam. This allows manipulating both the magnitude and the orientation of the native birefringence in a permanent way. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117007

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

Single‐mode and single‐beam emission have been achieved from surface emitting laser diodes based on the surface‐mode‐emission technique. By employing an optimized device design and a first‐order grating coupler, the laser diodes show under pulsed operation condition a single‐mode emission with a linewidth of 0.11 nm. A power up to 3.6 mW is emitted into a single, surface‐emitted beam, which has a beam divergence of 0.20°. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117008

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

In this letter the photoemissive properties of K–Te films produced under ultrahigh vacuum conditions are reported. K–Te photocathodes were fabricated by vapor deposition of Te and K onto a Mo substrate into the preparation chamber of the Free Electron Laser of the University of Twente. The highest quantum efficiency obtained at 259 nm was 11.1%, measured just after evaporation; this value decreased in a few minutes to a stable quantum efficiency of 8.3%. The reported results show that K–Te can be considered a promising material for the use as a photocathode in photoinjectors. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117009

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We determine the resolution of high‐performance confocal microscopes by measuring the three‐dimensional point–spread function (3D‐PSF) of an optimized confocal setup. The 3D‐PSF is standardized by recording the scattered light of pointlike objects. For a wavelength of 543 nm and a specified numerical aperture of 1.4 (oil), we find an axial and lateral focal full width at half‐maximum (FWHM) of 460±20 and 145±10 nm, respectively. A high signal‐to‐noise ratio is obtained by using recording times comparable to those of near‐field scanning optical microscopy. We further reduce the effective PSF extent by means of a three‐dimensional deconvolution technique exploiting the information gained from the measurement of the focus. We show that it is possible to obtain an axial and lateral FWHM of the far‐field effective PSF after deconvolution of 80 and 40 nm, respectively. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117010

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We report the transient response of wavelength switching in multicavity laser diodes. Spatially separated Bragg gratings embedded in a single fiber are used to map optical emission wavelength to photon round‐trip time in an external cavity mode‐locked laser diode. Transient emission wavelength and mode‐locked pulse formation are explored by switching applied radio frequency modulation. Initial conditions are found to dominate transient response. A hot photon cavity has a characteristic rise time corresponding to approximately two photon cavity round trips. A cold photon cavity exhibits significant turn‐on delay and rise time that depends on applied radio frequency signal power and is independent of above threshold steady‐state current bias. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117011

出版商:AIP    

年代:1996

数据来源: AIP

摘要:

We describe a method to microfabricate a light emitting diode array with pixels based on conjugated electroluminescent polymers sandwiched between appropriate electrodes. This method, based on direct photoablation with the 193 nm emission of an excimer laser, maintains the properties of these unique polymers. The technique as described here has already achieved an array of 20 &mgr;m×20 &mgr;m pixels with enhanced electroluminescence (EL) from these pixels and possible spectral tuning of the EL by the application of varying external field. This method can be extended to achieve nanometer dimensionalities using near‐field nanolithography. ©1996 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.117012

出版商:AIP    

年代:1996

数据来源: AIP