摘要:

We present a theory that should explain the operation of the apertureless near‐field optical microscope in the limit of smooth variations of both the refractive index and the corrugation of the object. Special emphasis is made on ultimate resolution and the recent experiments by F. Zenhausern, M. P. O’Boyle, and K.H. Wickramasinghe [Appl. Phys. Lett.65, 1623 (1994)]. We show that, in order to obtain resolution better than 7 nm, the variation of the object refractive index has to satisfy severe conditions. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113366

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We report the observation of all‐optical switching in a metal–semiconductor–metal waveguide structure. A silicon‐on‐insulator waveguide with aluminum interdigitated fingers deposited on the surface and overcoated with amorphous silicon provided high‐efficiency coupling and switching of Nd:YAG laser pulses. This structure is fully compatible with very large scale integrated manufacturing processes and represents a substantial leap forward in the quest for full‐scale integration of silicon‐based optoelectronic systems. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113367

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The lasing performance and wavelength tunability of a novel high efficiency copolymer poly[(2, 5, 2‘, 5‘‐tetraoctyl)‐p‐terphenyl‐4,4‘‐ylene vinylene‐p‐phenylene vinylene], TOP‐PPV, pumped with third harmonic radiation of a Nd:YAG laser, was studied in various organic solvents. The results were compared with Coumarin 120 and Coumarin 47 in ethanol under identical experimental conditions. The efficiency of the TOP‐PPV copolymer in hexane exceeds that of both coumarin dyes with more than 50%. The laser emission of the polymer dye in hexane is tunable in the wavelength region between 414 and 456 nm (&Dgr;&lgr;=38 nm). ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113368

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A new scanning near‐field optical microscopy based on the surface plasmon resonance is presented. Enhanced fields are localized at individual surface irregularities by the scattering of plasmons and the scattered plasmons produce a conical radiation. Variations in the conical radiation intensity caused by interactions between a raster‐scanned probe tip and the enhanced fields are recorded and related to the surface topography, providing an optical image with lateral resolution exceeding the diffraction limit. This technique is compared to complementary atomic force microscopy and scanning tunneling microscopy measurements and potential advantages are discussed. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113369

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Quasi‐phase‐matched second‐harmonic generation is observed in an AlGaAs waveguide. The AlGaAs waveguide is epitaxially grown on a template substrate where a periodic crystal domain inversion is achieved using wafer bonding and organometallic chemical vapor deposition. A scanning electron micrograph of the waveguide cross section reveals a distinct propagation of the crystal domain boundaries in the epitaxial growth direction. Second‐harmonic generation measurements on a fabricated rib‐loaded waveguide show a clear quadratic dependence of the second‐harmonic power to the input fundamental power. The peak conversion efficiency is 4.9%/W whereas the theoretical value is 124%/W for an ideal waveguide with no loss and with equal domain dimensions. A significant increase in the conversion efficiency is expected with reduced scattering losses realized by improved epitaxial growth and fabrication processes. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113370

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

We show that a buried oxide layer forming a current aperture in an all epitaxial vertical‐cavity surface emitting laser has a profound influence on the optical and electrical characteristics of the device. The lateral index variation formed around the oxide current aperture leads to a shift in the cavity resonance wavelength. The resonance wavelength under the oxide layer can thus be manipulated, independent of the as‐grown cavity resonance, by adjusting the oxide layer thickness and its placement relative to the active region. In addition, the electrical confinement afforded by the oxide layer enables record low threshold current densities and threshold voltages in these lasers. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113371

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

Blues pulses 300 fs long have been generated from 150 fs infrared pulses by compressing second harmonic radiated in the Cerenkov geometry. Mode‐locked Ti:sapphire pulses were prism coupled into a 1‐cm long proton‐exchanged MgO:LiNbO3planar waveguide. The 2 ps Cerenkov output, chirped due to group velocity mismatch, was then compressed by a diffraction grating down to 300 fs. The use of mode‐locked pulses results in a conversion efficiency of 1000%/W/cm, three orders of magnitude higher than by cw doubling in the same geometry. The Cerenkov geometry ensures that all wavelengths can be phase matched over long crystal length, so that even low power lasers can be efficiently doubled. The dispersion element ensures that the chirped output can be compressed into the femtosecond regime. This concept can be extended to femtosecond pulses in any two‐photon process in any waveguide material and any mode‐locked source. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113372

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The intensity noise in Fabry–Pe´rot lasers with low facet reflectivities is studied. A direct comparison between laser intensity fluctuations under noise suppressed and shot‐noise limited current injection is made. Noise levels in excess of the shot‐noise level are observed, even when the pump noise is suppressed. Also, an injection current dependent negative correlation between the intensity noise at the output facets of a laser is demonstrated. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113373

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

A novel external cavity configuration for stable single frequency operation of the semiconductor laser is demonstrated. By using an erbium doped fiber as the external cavity, longitudinal mode‐hopping is suppressed, ensuring single frequency operation. Employing a 3 m long fiber cavity, resolution‐limited optical linewidths of a kHz are obtained. ©1995 American Institute of Physics.

ISSN:0003-6951    

DOI:10.1063/1.113374

出版商:AIP    

年代:1995

数据来源: AIP

摘要:

The feasibility of population inversion is studied for the SiGe/Si system and compared with that of GaAs/AlGaAs. Because of the absence of strong polar optical phonon scattering in SiGe/Si, the lifetime difference of the upper and lower lasing levels, to which the population inversion and laser gain are proportional, is consistently an order of magnitude larger than that of GaAs/AlGaAs; nor does it show the sudden drop to zero or negative values when the lasing energy exceeds the optical phonon energy. Both systems studied are superlattices, each period of which consists of three coupled quantum wells and barriers. ©1995 American Institute of Physics. 

ISSN:0003-6951    

DOI:10.1063/1.113375

出版商:AIP    

年代:1995

数据来源: AIP