Shift-invariant interpattern association neural network

A shift-invariant neural network that uses the translation-invariant property of the modulus Fourier spectra with the heteroassociation interpattern association memory is proposed. A binary encoding of a spectral sampling of the training set is used to preserve the main features. Computer simulations and experimental demonstrations are provided that show the shift-invariant property of the proposed optical neural network.     

Derivation of algorithms for phase-shifting interferometry using the concept of a data-sampling window

I propose a systematic way to derive efficient, error-compensating algorithms for phase-shifting interferometry by integer approximation of well-known data-sampling windows. The theoretical basi of the approach is the observation that many of the common sources of phase-estimation error can be related to the frequency-domain characteristics of the sampling window. Improving these characteristics can therefore improve the overall performance of the algorithm. Analysis of a seven-frame example algorithm demonstrates an exceptionally good resistance to first- and second-order distortions in the phase shift and a much reduced sensitivity to low-frequency mechanical vibration.     

Fiber-linked telescope array: description and laboratory tests of a two-channel prototype

We present a complete two-telescope version of a fiber-linked coherent array that is meant to be used for mounting on the dish of a radio telescope. This was built with 20-cm amateur telescopes and includes three different servo subsystems for guiding, nulling of the air path difference, and fiber length control. Laboratory tests of the fully integrated system in front of a star simulator are described.     

Synthetic circular-harmonic phase-only filter for shift, rotation, and scaling-invariant correlation

A synthetic circular-harmonic phase-only filter is described. With this filter and a Fourier-transform correlator it is possible to obtain shift, rotation, and scaling-invariant correlations.     

Regenerative-feedback mode-locked dye laser: influence of the acousto-optic mode locker

A regenerative-feedback AM-mode-locked Rhodamine 6G dye laser is described. The laser delivers pulses of 0.8-ps duration with 40-mW average output power. The influence of the acousto-optic modulator on the output spectra, which came to be important for broad-bandwidth lasers, is also discussed.     

Design of a photowritten cavity neodymium-doped fiber laser tunable around an absorption molecular line

Experiments have shown that it is possible to realize laser cavities photowritten within rare-earth-doped silicate fibers. Experimental results on a particular application, namely, the detection of gas traces by identification of one of the gas's absorption lines, are presented. Experiments on an absorption line of atmospheric water have been carried out to illustrate this purpose. Two lasers have been designed with particular characteristics (spectral linewidths, slope efficiencies, thresholds). Preliminary experimental results on the detection of an absorption line of atmospheric water have been obtained with fiber lasers and optoacoustic detection.     

Tunable picosecond blue and ultraviolet pulses from a diode-pumped laser system seeded by a gain-switched laser diode

Picosecond pulses emitted from a gain-switched laser diode have been amplified in a Ti:sapphire regenerative amplifier indirectly pumped by a 4-W laser diode. This all-solid-state system produced microjoule pulses tunable from 803 to 840 nm at repetition rates up to 25 kHz with durations of 70-100 ps. By frequency doubling and tripling the output, we generated blue and UV pulses tunable from 401 to 420 nm and from 268 to 280 nm, respectively. Average powers larger than 4 mW were reached in these two wavelength regions.     

The "new science" of wetland restoration

The intricate workings of natural wetlands are slowly yielding their secrets to scientists applying a number of experimental approaches.