摘要:

We have used a bias-induced annealing process to improve the initial performance and the reliability of red (680 nm)Ga.46In.54Pvertical-cavity surface-emitting lasers. Measurements showed improved cathodoluminescence efficiency and increased current collection efficiency after the anneal. Trap concentration is believed to be reduced by the bias-induced annealing process. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121320

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Photopumped, pulsed, narrow line laser emission is demonstrated using cylindrical microcavities formed by &pgr;-conjugated polymer thin films wrapped around thin glass optical fibers and metal wires with various diametersD. A variety of cavity-dependent resonant laser mode structures were observed, which forD<10 &mgr;mcontain a single resonant spectral line of less than 1 Å in width. The microring lasers are also characterized by a well-defined, very low threshold excitation intensity, at which beam directionality and polarization degree dramatically increase. These findings open up the fields of lasers and fiber optics to organic materials. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121189

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

High-resolution x-ray microscopy makes use of nanostructured diffractive optics such as Fresnel zone plates made of nickel. These micro zone plates are manufactured using microscopic galvanoforms and electrodeposition techniques. Copolymer galvanoforms for nickel micro zone plates were irradiated with high doses of x-ray radiation to increase the degree of cross-linking of the copolymer network; in this way, exact pattern replication in the galvanoform was obtained for zone aspect ratios of up to 8:1. Using these galvanoforms, nickel micro zone plates were produced for the soft x-ray wavelength &lgr;=2.4 nm, with smallest zone widths of 30 nm and 40 nm, achieving first-order diffraction efficiencies of up to 13&percent; and 20&percent;, respectively. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121190

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Optical superlatticeEr:LiNbO3was fabricated by inducing a periodic ferroelectric domain structure into the crystal during the growing process. Because of the combination of the nonlinear optical properties ofLiNbO3and the spectral properties ofEr3+,the crystal can simultaneously emit the second harmonic light through quasi-phase matching and the green light through upconversion at room temperature. Pumped by infrared diode lasers, violet-and-green and blue-and-green light generation was demonstrated in two samples. The detailed absorption spectrum and emission spectrum of upconversion were measured. The possible physical mechanism was discussed. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121191

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We have mapped the internal pump intensity distribution of an optically pumped vertical-cavity surface-emitting laser. Spontaneous emission from quantum wells placed throughout the distributed Bragg reflectors is correlated to the pump intensity. The emission is monitored along the cleaved edge using the high spatial resolution and shallow depth of field provided by near-field scanning optical microscopy. Our results show a distinct buildup of optical intensity between the mirror stacks. Simulations performed using the transfer matrix method match well with the experimental data. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121192

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Double-fused vertical-cavity surface-emitting lasers (VCSELs) have demonstrated the highest temperature performance of any 1.5 &mgr;m VCSEL, but further optimization is needed to reduce their temperature sensitivity. We present and analyze threshold current measurements of these devices between−90 °Cand 30 °C stage temperature. Despite a zero gain peak offset from the emission wavelength at room temperature, the pulsed threshold current has its minimum near−50 °Ccorresponding to about−30 nmgain offset. This is in contrast to a common VCSEL design rule. Temperature effects on the optical gain of the strain-compensated InGaAsP/InP active region are found to be the main cause for the disagreement. A design rule modification is proposed. Numerical simulation of an optimized 1.55 &mgr;m VCSEL shows that gain offset improvements are counteracted by loss mechanisms. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121318

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The wavelength dependence of the third-order nonlinear optical susceptibilities,&khgr;(3),of theAu:TiO2composite films with Au concentration varying from 15&percent; to 60&percent; (volume fraction), was measured by a degenerate four-wave mixing (DFWM) technique using a probe laser with a pulse width of 200 fs. It was found that, with the wavelength of the probe laser close to the surface plasmon resonance(∼680 nm),both the&khgr;(3)and the figure of merit,&khgr;(3)/&agr;(&agr; is optical absorption coefficient) were significantly enhanced. The maximum value of the&khgr;(3)was6×10−7 esuand occurred at an Au concentration of about 38&percent;. Femtosecond time-resolved DFWM measurements revealed that the response time of the optical nonlinearity in theAu:TiO2films is extremely fast. The time-resolved DFWM results suggest that the main physical mechanism involved in the optical nonlinearity inAu:TiO2films on the femtoseconds time scale is the interband electric–dipole transition, and the hot electron excitation only partially contributes to the&khgr;(3)on the femtosecond time scale and it becomes dominant only in the picosecond region. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121193

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

We observe a light-induced on–off switching of the selective donor–acceptor pair excitation in bulk-grown semi-insulating GaAs. The spectral dependence of the switching process is related to the metastability of the EL2 defect. In the ground state, this As-antisite related midgap donor compensates the shallow acceptors and is responsible for the semi-insulating properties of the material. The loss of the shallow acceptor compensation, that accompanies the transfer of the EL2 to its metastable state leads to the observed absorption and luminescence quench of the shallow donor–acceptor pairs. We exploit these effects in demonstrating optical data storage in semi-insulating GaAs. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121194

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A metal nanoparticle system has been prepared by 200 KevAg+ion implantation into perfect single crystalSiO2at room temperature to dose:6.7×1016/cm2.The system presents quasidual-layer structure: the shallower implanted layer containing noninteracting small Ag nanoparticles and the deeper layer containing interacting large nanoparticles, in which great red shift, about 1 eV, comparing with the plasmon resonance frequency of the noninteracting nanoparticle, can be clearly observed. The red shift is attributed to the multipoles interaction among the high density nanoparticles at external electric field. Moreover, the magnitude of red shift increases with implanted dose. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121196

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Plasma-based ion implantation of the inner surface of a short, cylindrical tube is modeled using a two-dimensional particle-in-cell simulation. An auxiliary electrode, here a coaxial anode, is used to increase the ion impact energy. Initially, ions inside the tube impact the inner surface at approximately normal angles. At later times, ions enter the tube from the exterior plasma and impact predominantly near its center at glancing angles. Ions are found to cross the midplane of the tube and in some cases to pass completely through the tube, in contrast to the predictions of the “collisionless” fluid model. The total incident dose is greatest around the center of the tube, and least at its ends. ©1998 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.121188

出版商:AIP    

年代:1998

数据来源: AIP