摘要:

The characteristics of polarization self-modulation in a vertical-cavity surface-emitting laser (VCSEL) were studied for frequencies up to≈9 GHz both experimentally and theoretically. Polarization self-modulation was obtained by rotating the linearly polarized output of the VCSEL by 90° and reinjecting it into the laser. Experimentally we simultaneously recorded time traces, optical and radio-frequency spectra. We found for increasing modulation frequencies that the output characteristics changed from square-wave to sinusoidal and the VCSEL system assumed new polarization eigenstates that are different from the free-running VCSEL eigenstates. We modeled polarization self-modulation as an interband process and found a good qualitative agreement between our experimental and numerical results. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121398

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The static second-order hyperpolarizabilities&ggr;of armchair nanotubesC60+i×10are studied. Their magnitudes obey a scaling law given by&ggr;/&ggr;60=(1+i/6)3.15, where&ggr;60is the static&ggr;magnitude ofC60.Based on this law, as an example, we predict that the static&ggr;magnitude of armchair nanotube with a length of 40 Å generally seen in experiment is about3.5×10−29 esu, which is an appropriate value needed in photonic devices, and implies that armchair nanotube is an ideal candidate among all third-order materials for photonic applications. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121356

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Growth of high quality wurtzite-structure GaN layers on (111)MgAl2O4by gas source molecular beam epitaxy is described. Hydrazine was used as a source of active nitrogen.In situreflection high energy electron diffraction was used to monitor the growth mode. Two-dimensional growth was obtained at temperatures above 750 °C on multi-step GaN buffer layers. The resulting GaN films show excellent luminescence properties. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121357

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Ridged channel waveguides inKNbO3were fabricated by a technique usingHe+ion implantation, photolithographic masking, and subsequentAr+ion sputtering. A continuous-wave second-harmonic output power of 14 mW at 438 nm was obtained with an in-coupled fundamental power of 340 mW in a 0.73 cm long waveguide. Phase matching was provided by material birefringence without need of periodic poling. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121358

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The spectral characteristics of the internal(PO4tetrahedron) modes of fast-grownKH2PO4crystals under sub-damage threshold, 10 ns, 355 nm laser irradiation have been investigated. Pump-and-probe Raman spectroscopy indicates transient changes of the intensity of the915 cm−1,–PO4internal mode. This change is attributed to a transient increase of the absorption due to generation by the 355 nm pump pulse of electronic defects in the bulk of the crystal. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121389

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A 25-stage interband cascade laser with a W active region and a third hole quantum well for the suppression of leakage current has exhibited lasing in pulsed mode up to 286 K. A peak output power of 160 mW/facet and a slope efficiency of 197 mW/A per facet (1.1 photons per injected electron) were measured at 196 K. Above 200 K, the characteristic temperature was higher(T0=53 K)and the threshold current densities lower than for a previously reported W interband cascade laser without the third hole quantum well. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121359

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Persistent spectral hole-burning has been reported for singly, Eu-doped, and doubly, Eu- and Sm-doped, CaS phosphors. Efficient photon gated holeburning in the4f7(8S7/2)−4f65d1transition ofEu2+is a result of photoionization ofEu2+toEu3+.These holes have a width of<5 GHz(2 K), survive thermal cycling of the phosphor up to the room temperature, 300 K, and have no detectable deterioration over more than a day of storage time at low temperature (2 K). Although self-gated holeburning is observed with the reading laser at higher powers, the photon budget for reading these holes is so small that in excess of 1000 reading cycles can be performed without destroying the optical signal. The nature of holes burned by photon-gating is found to be very different from the self-gated holes. The characteristics for the holeburning are the same in singly and doubly doped phosphors, suggesting that under the conditions of our experiments, Sm traps do not play any significant role in spectral holeburning. Possibilities of high density optical memory storage using photon-gated holeburning in this THz broad transition are discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121360

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We report a resonant cavity enhanced (RCE) detector built around a three-dimensional photonic band gap crystal. The RCE detector was built by placing a monopole antenna within the localized modes of planar and boxlike defect structures. The enhanced electric field around these defect structures were then measured by a microwave detector and a network analyzer. We measured a power enhancement factor of 3450 for planar cavity structures. A Fabry–Perot cavity model was used to understand and predict resonant cavity enhancement in this structure. The tuning bandwidth of the RCE detector extends from 10.5 to 12.8 GHz, which corresponds to the full photonic band gap by the crystal. These RCE detectors have increased sensitivity and efficiency when compared to conventional detectors, and can be used for various applications. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121361

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Light-coupling masks (LCMs) based on structured organic polymers that make conformal contact with a substrate can constitute an amplitude mask for light-based lithographies. The LCM is exposed through its backside, from where the light is differentially guided by the structures towards the substrate. Images of arbitrarily shaped features having dimensions much smaller than that of the vacuum wavelength of the exposing light are formed in the resist in a 1:1 correspondence to their size in light-guiding portions of the mask. LCMs allow pattern replication at high resolution and densities over large areas in photoresist without the need for elaborate projection optics. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121362

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Light-emitting diodes ofpoly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEHPPV) are fabricated using sodium sulfonated polystyrene (SSPS) ionomer containing 10 mol &percent; ionic groups as an electron injecting and hole blocking material. When an electric field stronger than2.7×107 V/mis applied, SSPS in the indium–tin oxide ITO/MEH-PPV/SSPS/Al system causes a bridging effect between sodium ions and the Al cathode at the SSPS/Al interface, leading to excellent electron injection. Furthermore, the ionomer has a high band gap energy of∼5 eV,resulting in hole blocking. The operating voltage for the ITO/MEH-PPV/SSPS/Al is reduced by∼60&percent;and the relative quantum efficiency is enhanced by three orders of magnitude compared with those of the corresponding single-layer MEH-PPV device. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121363

出版商:AIP    

年代:1998

数据来源: AIP