Maria Chiara Ubaldi

All-optical pattern recognition for digital real-time information processing

To recognize digital streams of digital data, all-optical and passive techniques able to discriminate optical bit words in real time are presented. Discrimination capability of different correlators, both in free space architectures and in delay lines structures, is theoretically and experimentally analyzed. Experimental performances in word recognition are shown in the case of a volume holographic correlator, in the case of a lithographic phase-only-filter correlator, and in the case of a novel coherent delay lines correlator operating at the wavelength 1550 nm and at the bit rate of 2.5 Gbit/s.

Diffraction of optical communication Gaussian beams by volume gratings: comparison of simulations and experimental results

The diffraction effects induced by a thick holographic grating on the propagation of a finite Gaussian beam are theoretically analyzed by means of the coupled-wave theory and the beam propagation method. Distortion of the transmitted and diffracted beams is simulated as a function of the grating parameters. Theoretical results are verified by experimentation realized by use of LiNbO3 volume gratings read out by a 1550-nm Gaussian beam, typical of optical fiber communications. This analysis can be implemented as a useful tool to aid with the design of volume grating-based devices employed in optical communications.

In situ growth in a PMMA film of oriented nanocrystals of the hybrid inorganic–organic acentric material [(E)-N,N-dimethylamino-N′-methylstilbazolium][Cu5I6]

A poly(methyl methacrylate) (PMMA) composite film containing 4 wt% of the strongly second order NLO active ionic material [(E)-N,N-dimethylamino-N′-methylstilbazonium][Cu5I6] (1), obtained by spin coating of a CH3CN solution on a glass substrate, shows by a two step process (electric poling followed by controlled thermal annealing up to 140 °C) in situgrowth of nanocrystals, some of which are aligned, with a size of less than 400 nm as supported by TEM and GIXRD evidence. A long lasting second harmonic generation (SHG) is produced which is stable even after exposure to water vapour for one night.

Volume holography for 1550 nm digital data bases

It’s well known that volume holography makes it possible to record real information databases by overlapping multiple holograms within the same volume and accessing them independently. Furthermore in the last years the increasing achievement of optical communication systems operating in the third window of optical communication systems (1550nm) is giving a strong impulse to the implementation of all-optical devices useful to process Wavelength Division Multiplexed (WDM) information signals.

Narrow Linewidth and Compact External-Cavity Lasers for Coherent Optical Communications

In this chapter, the activities related to external-cavity laser development executed in CPqD will be presented in detail. The target application is high-speed and high-order modulation formats optical systems for telecom. Using cavity design techniques, a narrow linewidth and high output power laser suitable for manufacturing is presented. It is presented the operation principle of the tunable mirror which is used as channel selector for the external cavity. Experimental results of a fixed-wavelength prototype are presented, showing optical output power above 16 dBm, Side-mode Suppression Ratio (SMSR) of 60 dB, and linewidth around 75 kHz. The cavity shows good stability for long-term high-temperature storage.