Large-signal phase retardation with a poled electrooptic fiber

A linear electrooptic coefficient of 0.3 pm/V is induced in a germanosilicate fiber by thermal/electric-field poling. Reducing the fiber thickness by simple mechanical polishing following the poling, leads to a half-wave drive voltage of only 75 V for a 12-cm active length with no measurable linear optical loss in the fiber. The induced linear electrooptic coefficient shows no decay at room temperature for over four months, and only a 10% decay after heating to 90/spl deg/C for 1000 h.     

A CW external-cavity surface-emitting laser

Room temperature, continuous wave (CW) operation of an external-cavity, optically-pumped surface-emitting laser is reported. The device is a resonant-periodic gain (RPG) vertical-cavity surface-emitting laser (VCSEL) with the top mirror stack replaced by an epitaxially grown antireflection (AR) coating. An external mirror having a 50-mm radius of curvature completes the resonator in a near hemispherical configuration. Mode spectra, input-output curves, and polarization properties of the device are presented.     

Effect of hydrogen loading on temperature/electric-field poling ofSiO2-based thin films on Si

Waveguide stacks of GeSiO₂-based glass deposited on Si exhibit a permanent second-order nonlinearity following temperature electric-field poling. High temperature hydrogen loading increases the second harmonic signal under certain conditions     

Pump depletion and saturation of two-photon resonant third-harmonic generation processes

Theoretical efficiency limitations for a two-photon resonant third-harmonic generation (THG) process are analyzed in a treatment which includes all nonlinear processes associated with the two-photon resonance assuming negligible material excitation. Results are presented for both collimated-beam and tight-focusing geometries. The theory is applied to experimental results for THG of CO2laser radiation in liquid CO-O2mixtures; good agreement is found for the observed saturation in the THG efficiency in a tight-focusing geometry.     

Large Photosensitivity in Lead Silicate Glasses

A large photoinduced refractive index change (△n = 0.21 ± 0.04 ) is obtained in leadsilicate glasses by irradiation with the frequency quadrupoled output of a Q-switched YAG laser (266nm).     

Large Photosensitivity in Lead Silicate Glasses

A large photoinduced refractive index change (△n = 0.21 ± 0.04 ) is obtained in leadsilicate glasses by irradiation with the frequency quadrupoled output of a Q-switched YAG laser (266nm).     

Emission Reduction and Capacity Increase in GSM Networks by Single Antenna Interference Cancellation

There is an increasing demand to utilize the frequency spectrum of mobile communication systems most efficiently. This means in particular to GSM networks that the frequency reuse shall be planned as low as possible. In this case the system may become limited by interference rather than coverage. One promising technology for GSM mobiles in interference-limited systems is single antenna interference cancellation (SAIC). This receiver technology allows both for increasing the network capacity and for reducing the base station transmit power. The aim of this paper is to assess the emission reduction as well as the system capacity capabilities when SAIC technology is applied in downlink receivers.     

High-efficiency CW operation of MOCVD-grown GaAs/AlGaAs vertical-cavity lasers with resonant periodic gain

A GaAs/AlGaAs vertical-cavity surface-emitting laser with resonant periodic gain has been grown by metal-organic chemical vapour deposition. The as-grown structure exhibits an optically pumped CW threshold below 15 mW at 300 K and a single-ended power efficiency up to 45%. Fundamental Gaussian and higher-order modes are observed with spectral widths (FWHM) as low as 0.27 AA.<>     

Optical and Interferometric Lithography - Nanotechnology Enablers

Interferometric lithography (IL), the interference of a small number of coherent optical beams, is a powerful technique for the fabrication of a wide array of samples of interest for nanoscience and nanotechnology. The techniques and limits of IL are discussed with particular attention to the smallest scales achievable. With immersion techniques, the smallest pattern size for a single exposure is a half-pitch of /spl lambda//4n where /spl lambda/ is the optical wavelength and n is the refractive index of the immersion material. Currently with a 193-nm excimer laser source and H/sub 2/O immersion, this limiting dimension is /spl sim/34 nm. With nonlinear spatial frequency multiplication techniques, this limit is extended by factors of 1/2, 1/3, etc.-extending well into the nanoscale regime. IL provides an inexpensive, large-area capability as a result of its parallelism. Multiple exposures, multiple beams, and mix-and-match with other lithographies extend the range of applicability. Imaging IL provides an approach to arbitrary structures with comparable resolution. Numerous application areas, including nanoscale epitaxial growth for semiconductor heterostructures; nanofluidics for biological separations; nanomagnetics for increased storage density; nanophotonics including distributed feedback and distributed Bragg reflectors, two- and three-dimensional photonic crystals, metamaterials, and negative refractive index materials for enhanced optical interactions are briefly reviewed.