Optical OFDM for SiPM-Based Underwater Optical Wireless Communication Links.

Underwater optical wireless systems have dual requirements of high data rates and long ranges in harsh scattering and attenuation conditions. In this paper, we investigate the advantages and limitations of optical orthogonal frequency-division multiplexing (O-OFDM) signaling when a silicon photo-multiplier (SiPM) is used at the receiver in order to ensure high sensitivity. Considering a light-emitting diode (LED) transmitter and taking into account the limited dynamic range imposed by the transmitter and the SiPM receiver, we study the performance of three popular O-OFDM schemes, i.

Giant ultrafast optical nonlinearities of annealed SbTe layers.

The optimization of thin SbTe films in order to obtain giant ultrafast optical nonlinearities is reported. The ultrafast nonlinearities of the thin film layers are studied by the Z-scan technique. Giant saturable absorption is obtained, which is the highest ever reported, by means of the Z-scan technique.

Taking advantage of acoustic inhomogeneities in photoacoustic measurements.

This paper proposes a method for improving the localization and the quantification of the optical parameters in photoacoustic (PA) tomography of biological tissues that are intrinsically heterogeneous in both optical and acoustic properties. It is based on the exploitation of both the PA signal, generated by the heterogeneous optical structures, and the secondary acoustic echoes due to the interaction between a primary PA wave generated near the tissue surface and the heterogeneous acoustic structures. These secondary echoes can also be collected through proper measurements of the PA signals.

Nanosecond Z-scan measurements of the nonlinear refractive index of fused silica.

We present the results of Z-scan studies carried out on fused silica at 1064nm and 532nm with two different nanosecond pulse durations. Such measurements in silica and in the nanosecond regime are possible thanks to a high sensitivity setting up of the Z-scan method and in-situ characterizations of the spatio-temporal parameters of the beam. Besides, with the use of a newly adapted numerical simulation only the calibration errors of the measurement devices are significant.

Laser-induced damage of materials in bulk, thin-film, and liquid forms.

Accurate threshold curves of laser-induced damage (7-ns single shot at 1.064 microm) are measured in bulk and at the surfaces of optical components such as substrates, thin films, multilayers, and liquids. The shapes and the slopes of the curves are related to the spot size and to the densities of the nanodefects that are responsible for damage.