摘要:

The spontaneous emission rate from an In0.2Ga0.8As quantum well in a cylindrical dielectric cavity with submicron radii and without mirrors in the emission plane is calculated based on a rigorous description of the cavity modes and their interaction with the 2D electronic system. The rate is suppressed for radii much less than the peak optical wavelength (rcav≪&lgr;/n), enhanced by up to a factor of ≊8 forrcav≊&lgr;/n, and remains similar to its value in the absence of a cavity forrcav≫&lgr;/n. The emitted light produces a highly collimated vertical beam in the intermediate region with the majority of photons emitted into the guided cavity modes, and its spatial distribution broadens dramatically in the smallest structures. The global spectral width of spontaneous emission in cavities that can presently be fabricated is largely unaffected by the introduction of lateral dielectric boundaries. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115299

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A three‐terminal laser structure is proposed as a means to achieve laser modulation using dynamic carrier heating. The injection of hot electrons, with energy tuned by variable joule heating over a high electric field region, is used to govern the carrier temperature in the active layer of a laser, while a separate heterojunction controls the injection rate. Simulations show the possibility of generating good‐shaped picosecond optical pulses by modulating the voltage that controls the heating electric field. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115300

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The optical nonlinearity of a mode‐locking dye (Kodak 9740) under picosecond excitation at 532 nm, is studied using the Z‐scan technique. Theoretical fits to the data give a value of 3.2 cm/GW for the two‐photon absorption coefficient (&bgr;) and −2.1×10−5cm2/GW for the real part (&ggr;) of the nonlinearity. In addition, we demonstrate optical limiting using two‐photon absorption as well as self‐defocusing. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115301

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Polymeric 2×2 electro‐optic switches based on the balanced bridge, or Mach–Zehnder, design are presented. Two poled nonlinear optical side‐chain polymers based on the dye Disperse Red 1, one with a glass transition temperatureTgof 131 °C and the other with aTgof 228 °C, were used as the active layers in these devices. The switch designs incorporated traveling‐wave electrodes in the phase shift sections and, for the lowerTgpolymer device, electrically adjustable 3 dB couplers. At the 1.32 &mgr;m operating wavelength, extinction ratios of at least 28 dB were achieved in all four states of the lowerTgswitch with a propagation loss of 1.6 dB/cm and a small signal 3 dB modulation bandwidth of over 2 GHz. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115302

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The large signal dynamics of passively colliding pulse mode‐locked laser diodes is studied. We derive a model which explains modelocking via the interplay of gain and loss dynamics; no bandwidth limiting element is necessary for pulse formation. It is found necessary to have both fast and slow absorber dynamics to achieve mode‐locking. Significant chirp is predicted for pulses emitted from long lasers, in agreement with experiment. The pulse width shows a strong dependence on both cavity and saturable absorber length. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115303

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Discharge frequency dependence of growth of particulates is studied in high frequency silane plasmas. Particulates appear earlier after discharge initiation and the increasing rate of their amount in the subsequent phase decreases with increasing the discharge frequency from 3.5 to 28 MHz. Even in the early phase of their formation for all 3.5–28 MHz discharges, particulates grow principally around the plasma/sheath boundary near the powered electrode, where short lifetime radicals are actively generated. For 28 MHz, the density of particulates in the early discharge phase is extremely high (≥1011cm3). The latter two features suggest thatmanyshortlifetimeneutralradicals(such as SiH2), being produced at a high rate, significantly contribute to the nucleation and initial growth ofoneparticulate, at least, for a relatively high power density of the order of 0.5 W/cm2. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115304

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Deep‐etch‐definedGaAs/Al0.3Ga0.7Assquare features of multiquantum well material, with dimensions as small as 160 nm, have been fabricated using magnetron reactive ion etching (MIE). Luminescence spectroscopy shows confinement of charge carriers to the features’ center. The effects of rf power and etching time on the luminescence efficiency of these features and its concomitant etch‐induced damage are examined. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115305

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

166Er atoms were implanted with an energy of 70 to 90 keV and doses of 0.8 to 2.0×1017/cm2into Si(111) substrates at temperatures ranging from 450 to 530 °C. We found that using conventional nonchanneled implantation at energies of ∼90 keV, it is impossible to form a continuous ErSi1.7layer. At best, after annealing, a discontinuous ErSi1.7layer with poor crystalline quality (&khgr;min=40%) is obtained. On the contrary, using channeled implantation, a continuous epitaxial ErSi1.7layer with very good crystalline quality can be formed; a lowest &khgr;minvalue of 1.5% for a surface ErSi1.7layer has been obtained. The origin of this different behavior is explained. Our results show that for synthesizing continuous ErSi1.7layers with good quality using ion beam synthesis at energies around 90 keV, channeled implantation is indispensable. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115306

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Photoelectron spectra of a Si wafer, on which copper phthalocyanine was evaporated with a thickness of 50 A˚, were measured using grazing incidence x rays under a total reflection condition. It was observed that the backgrounds owing to inelastic electron scattering in solids were reduced. It was also observed that the substrate Si signal was removed and that surface signal was enhanced due to the total x‐ray reflection. Oxygen depth was determined using the angle dependence of the x‐ray photoelectron spectral intensity. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115307

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

An application of photoacoustic technique is developed for determining the thermal diffusivity coefficient and the thermal conductivity of transparent materials. The backing material which supports the sample is made optically opaque, i.e., it entirely absorbs the incident light, and the converted heat diffuses through the sample heating the gas in contact with its opposite surface. The method is illustrated by fitting voltage amplitude and phase signals versus the chopping frequency in the photoacoustic cell, according to a theoretical model of heat diffusion. Thermal parameters obtained for three polymers compare very well with results from the literature. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.115308

出版商:AIP    

年代:1995

数据来源: AIP