Biomedical subjects

Albert Le Floch

Publications and source records attributed to Albert Le Floch.

4 recordsLinked to original sources

PubMed2004

Nonequivalence of spatial shifts and Wigner delays at interfaces.

We isolate spatial shifts and Wigner delays for reflection at the same interface and demonstrate that they can carry different information. The spatial shifts associated with Wood anomalies on gratings can be either positive or negative, while the corresponding delays are both positive. In the standard case of total reflection at a glass-air interface, a differential two-photon absorption correlation technique allows us to measure for the first time a delay of up to 35 fs in agreement with the associated 10.5 microm spatial shift. The method also allows us to isolate giant Wigner delays. The existence of similar delays in different areas of physics is discussed.

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PubMed2003

Continuous-wave tunnel ring fiber laser.

The continuous-wave oscillation of a tunnel ring fiber laser is demonstrated. The high losses encountered in tunneling systems are compensated for by a high-gain amplifying medium from barrier widths for 0 to lambda/2. The experimental observations are in good agreement with a simple theoretical model. This near-field probe system allows one to detect small displacements in the picometer range.

Journal Article↗

PubMed2003

Jamin Fabry-Perot interferometer.

A novel type of interferometer was designed and tested experimentally. It combines the advantages of the spatial path separation used in the two-wave polarized Jamin interferometer and the high sensitivity that characterizes the multiwave Fabry-Perot interferometer. Furthermore, when it is sandwiched between crossed polarizers it shows a sensitivity to intracavity anisotropies that is proportional to the square of the Fabry-Perot interferometer's finesse.

Journal Article↗

PubMed2002

Building blocks for a two-frequency laser lidar-radar: a preliminary study.

A new principle of lidar-radar is theoretically and experimentally investigated. The proposed architecture is based on the use of an rf modulation of the emitted light beam and a direct detection of the backscattered intensity. Use of a radar-processing chain allows one to obtain range and Doppler measurements with the advantages of lidar spatial resolution. We calculate the maximum range of this device, taking into account different possible improvements. In particular, we show that use of a pulsed two-frequency laser and a spatially multimode optical preamplification of the backscattered light leads to calculated ranges larger than 20 km, including the possibility of both range and Doppler measurements. The building blocks of this lidar-radar are tested experimentally: The radar processing of an rf-modulated backscattered cw laser beam is demonstrated at 532 nm, illustrating the Doppler and identification capabilities of the system. In addition, signal-to-noise ratio improvement by optical pre-amplification is demonstrated at 1.06 microm. Finally, a two-frequency passively Q-switched Nd:YAG laser is developed. This laser then permits two-frequency pulses with tunable pulse duration (from 18 to 240 ns) and beat frequency (from 0 to 2.65 GHz) to be obtained.

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