摘要:

Theoretical and experimental studies on guided-wave acousto-optic (AO) Bragg diffraction in a composite indium gallium arsenide phosphide (InGaAsP) planar waveguide were carried out. In this letter, the experimental results of the excitation and propagation of a ⟨110⟩-directed surface acoustic wave (SAW) at the center frequency of 167 MHz, and the AO Bragg diffraction at a 1.31 micron wavelength inIn0.22Ga0.78As0.47P0.53waveguide are reported. An AO Bragg diffraction efficiency as high as 14&percent; was achieved at an acoustic drive power of 8.5 mW with an interaction length (transducer aperture) of only 1.0 mm. Two orders of magnitude improvement in the Bragg diffraction efficiency versus rf drive power should be achievable by the optimization of the SAW transducer and the optical waveguide parameters. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119153

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The properties of InAsSb/InAsP strained-layer superlattice (SLS), midwave infrared materials, and devices are reported. SLSs were grown by metal-organic chemical vapor deposition and characterized by magnetophotoluminescence and x-ray diffraction. Excellent performance was observed for an SLS light emitting diode (LED) and an optically pumped SLS laser. The semimetal injected, broadband LED emitted at 4 &mgr;m with 80 &mgr;W of power at 300 K and 200 mA average current. The laser displayed 3.86 &mgr;m emission at 240 K, the maximum operating temperature of the laser, and a characteristic temperature of 33 K. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119154

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Gain narrowing and lasing from a soluble, highly photoluminescent conjugated polymer,poly(2-butyl, 5-(2′-ethyl-hexyl)-1,4-phenylene vinylene)(BuEH-PPV), are compared using two resonant structures: planar waveguides and microcavities. The gain narrowing and lasing thresholds are comparable, 0.05–0.1 &mgr;J (10 ns pulse focused to∼1.5 mm). Gain narrowing is not observed in films on indium tin oxide (ITO) unless a cladding layer is placed between the BuEH-PPV and ITO. Single-mode microcavity lasers are obtained when a cavity resonance occurs at the wavelength where the gain of the polymer is maximum. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119156

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

A novel tandem SiGe–Si device is demonstrated which, based on different photoresponses in two back-to-back diodes, exhibits a voltage tunable spectral responsivity. This feature, in conjunction with a wavelength dependence in the current direction, allows the efficient decryption of a signal when substantial noise is added to distinct carrier frequencies. Time dependent encryption schemes are also possible via a modulated voltage bias. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119155

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Intersubband stimulated emission under optical pumping has been observed in the conduction band of GaAs–AlGaAs quantum wells. The asymmetric coupled quantum wells which exhibit three conduction bound levels are designed to exhibit population inversion under optical pumping. An optical excitation at&lgr;=9.2 &mgr;mis used to bleach the absorption between the ground and second excited subband. The population inversion between excited subbands is pumped and probed on a picosecond time scale by a tunable two-color free-electron laser. The stimulated amplification is studied at low temperature in infrared waveguides as a function of the waveguide length and of the probe wavelength. A stimulated gain≈80 cm−1is measured at 12.5 &mgr;m in agreement with calculations. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119125

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

The experimental realization of a new ultraviolet and blue tunable fiber Raman laser, based on a simple double-pass fiber laser arrangement with Littrow-prism-tuned emission, is demonstrated. The third harmonic of aQ-switched Nd:YAG laser(&lgr;p=355 nm)is used to pump a 100-&mgr;m-core-diam multimode silica UV optical fiber. As a result of a single pass of the pump laser emission through the fiber, an initial multicascade Raman Stokes spectrum that contains up to 21 Stokes orders in the spectral range 360–527 nm at1.9 GW/cm2input pump intensity is generated. By using the double-pass regime of the fiber Raman laser and multimode fibers with different lengths, a discretely tunable generation corresponding to the various Stokes orders over the multicascade Stokes spectrum in the ultraviolet and blue regions (360–493 nm) is obtained. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119126

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

In this letter, we present results of a study of the magneto-optical Kerr response in Co/Pt superlattices by solving for optical constants and Voigt parameters of constituent layers in the structure. The absolute values of the Voigt parameters of Co/Pt interfaces were found to be about twice as large as for the Co layer in the superlattice. Furthermore, using the determined optical constants and Voigt parameters, we can generate the Kerr rotations and ellipticities for Co/Pt superlattices or sandwich structures with continuously changed layer thicknesses and different repeat numbers. Comparison of these theoretical results to the experimental magneto-optical responses for selected structures exhibits strong consistency. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119152

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

An aluminum nitride thin film on sapphire substrate was prepared by metal–organic chemical-vapor deposition for optical waveguide study. A rutile prism coupler was employed to display the waveguide modes (Nlines) with wavelengths of 632.8, 532.1, 514.5, and 488.0 nm. The refractive index and thickness of the waveguide material were obtained by prism–coupler measurement. The parameters in the dispersion equation were determined by curve fitting. The attenuation in the waveguide was evaluated by scattering loss measurements using a fiber probe. The attenuation coefficient &agr; is in the range of1.5–2.1 cm−1(5.4–7.6 dB cm−1),depending on the surface roughness of the sample and different orders of waveguide modes. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119127

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

Spectroscopic ellipsometry (SE) together with the optical transmission method is successfully used to determine the refractive indexnand absorption coefficient &agr; of undoped gallium nitride film over the spectral range of 0.78–4.77 eV of photon energy. The SE measurement is carried out at angle of incidence of 60° over the 1.5–4.77 eV energy range and optical transmission measurement over the 0.78–3.55 eV energy range. The refractive indexnand absorption coefficient &agr; obtained by both methods show unique results in the overlap wavelength region. Refractive indexnis found to follow the Sellmeir dispersion relationshipn2(&lgr;)=2.272+304.72/(&lgr;2−294.02)below the fundamental band edge. A free excitonic structure at the band is clearly observed at room temperature, with the transmission energy of free exciton at 3.44 eV, which is in reasonable agreement with the reported results. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119157

出版商:AIP    

年代:1997

数据来源: AIP

摘要:

We present calculations of the differential gain and threshold current densities for a 3.7 &mgr;m multiple quantum well structure consisting of a “well” composed of several periods of an InAs/InGaSb superlattice alternating with a quinternary alloy “barrier.” We find serious limitations to the optical properties of active regions composed of these multiple quantum wells, and propose a four-layer superlattice structure which corrects these problems. ©1997 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.119128

出版商:AIP    

年代:1997

数据来源: AIP