Mauro Benedetti

Private Message Transmission by Common Driving of Two Chaotic Lasers

In this paper, we numerically demonstrate private data transmission using twin semiconductor lasers in which chaotic dynamics and synchronization are achieved by optical injection into the laser pair of a common, chaotic driving-signal, generated by a third laser subject to delayed optical feedback. This laser is selected with different parameters with respect to the twin pair, so that the emissions of the synchronized, matched lasers are highly correlated, whereas their correlation with the driver is low. The digital message modulates the emission of the transmitter, as in a standard CM scheme. Message recovery is then obtained by subtracting, from the transmitted chaos-masked message, the chaos, locally generated by the synchronized receiver laser. Simulations have been performed with the Lang-Kobayashi model, keeping into account both laser and photodetector noise. Private transmission has been demonstrated by investigating the effect of the parameter mismatch, between transmitter and receiver, on synchronization and message recovery.

Message Encryption by Phase Modulation of a Chaotic Optical Carrier

We present a numerical and experimental evaluation of message encryption by phase modulation, using a chaotic optical carrier generated by a laser subject to delayed optical feedback. This method offers better security than the conventional amplitude masking, where the signal is simply added to the chaotic waveform

Secure Chaotic Transmission on a Free-Space Optics Data Link

In this paper, we numerically demonstrate secure data transmission, using synchronized ldquotwinrdquo semiconductor lasers working in the chaotic regime, which represent the transmitter and receiver of a cryptographic scheme, compatible with free-space optics technology for line-of-sight communication links. Chaotic dynamics and synchronization are obtained by current injection into the laser pair of a common, chaotic driving-signal. Results of simulations are reported for the configuration in which the chaotic driving-current is obtained by photodetection of the emission of a third laser (driver), chaotic by delayed optical feedback in a short cavity scheme, selected with different parameters with respect to the laser pair. The emissions of the synchronized, matched lasers are highly correlated, whereas their correlation with the driver is low. The digital message modulates the pumping current of the transmitter. Message recovery is performed by subtracting the chaos, locally generated by the synchronized receiver laser, from the signal obtained by photodetection (at the receiver side) of the chaos-masked message transmitted in free space. Simulations have been performed with the Lang-Kobayashi model, keeping into account both attenuation of the optical signal in a line-of-sight configuration, and noise. Security has been investigated and demonstrated by considering the effect, on synchronization and message recovery, of the parameter mismatch between transmitter and receiver.

Silicon micromachined periodic structures for optical applications at λ=1.55μm

In this letter, the authors report the design, fabrication, and characterization of a silicon micromachined periodic structure for optical applications at λc=1.55μm. The microstructure, which can be envisioned as a one-dimensional photonic crystal, is composed of a periodic array of 1-μm-thick silicon walls and 2-μm-wide air gaps, each one corresponding to a different odd number of quarter wavelength at λc (hybrid quarter wavelength). The fabrication is based on the electrochemical etching of silicon, yielding parallel trenches with depths up to 100μm. Preliminary reflectivity measurements show the presence of a band gap at λc=1.55μm, as theoretically expected.

Multi-User Private Transmission With Chaotic Lasers

In this paper, we propose a scheme for private data transmission using chaotic lasers, which is derived from the well-known public key cryptography. With this new approach, it is possible to exchange data between any couple of subscribers in a network, while schemes based on chaotic lasers are usually restricted to transmission between two specific users, sharing a twin laser pair. This is possible by introducing a provider, who is responsible of the network security. For each subscriber a couple of twin chaotic lasers is required, one being held by the provider and the other by the subscriber himself. The basic two-laser scheme of chaotic transmission is then used for secure data exchange, both between two subscribers and between a subscriber and the provider. Several arrangements can be considered, based on this architecture, including the use of an electro-optical repeater, which is studied in detail in this paper. More advanced solutions can be also implemented, e.g., using a three-laser scheme. The Lang-Kobayashi model is used for simulations. Experiments are performed using InP-integrated modules.

Chaos Generation and Synchronization Using an Integrated Source With an Air Gap

We discuss experimentally and numerically the dynamical behavior of a novel integrated semiconductor laser subject to multiple optical feedback loops. The lasers structure consists of distributed feedback section coupled to a waveguide, an air gap section and two phase sections. It is found that the laser, due to the multiple feedback loops and under certain operating conditions, displays chaotic behaviors appropriate for chaos-based communications. The synchronization properties of two unidirectionally coupled (master-slave) systems are also studied. Finally, we find numerically the conditions for message encryption/extraction using the multiple-feedback lasers.

All-Optical Wavelength Conversion of a Chaos Masked Signal

Wavelength conversion in the transmission of a message masked by optical chaos is experimentally demonstrated. In our setup, chaos is generated by a distributed-feedback laser subject to delayed optical feedback, and hides a message by additive chaos masking. The optical wavelength is converted, along the transmission line, by four-wave mixing in a semiconductor optical amplifier. At the receiver, the message is extracted by master-slave synchronization. Our experiments demonstrate that secure communications based on chaos are compatible with channel switching as required in reconfigurable optical networks.

Reflection properties of hybrid quarter-wavelength silicon microstructures

The authors present experimental and numerical results relative to the polarization-resolved spectral reflectivity of one-dimensional periodic microstructures, evaluated in the near-infrared region at non-normal incidence. The tested hybrid quarter-wavelength microstructures, fabricated by electrochemical deep etching of silicon, consist of arrays of silicon walls and air gaps, with 3 and 4μm periods and aspect ratio of up to 100. A theoretical Monte Carlo analysis taking into account the presence of a Gaussian statistical distribution for the structure porosity has been carried out and the calculated wavelength dependence of the reflectivity at non-normal incidence has been confirmed by experimental data.

Spot optical measurements on micromachined mirrors for photonic switching

This paper describes and compares three optical methods for performing spot measurements on micromachined mirrors, designed for photonic switching in fiberoptic networks. For static characterization, two spot-position detection systems, one based on a vidicon camera and the other based on a bidimensional silicon position sensitive detector (PSD), are illustrated, tested, and compared. Moreover, the dynamic behavior has been monitored with the PSD-based detection arrangement and with a semiconductor laser feedback interferometer. Advantages and drawbacks of these methods are highlighted. Testing is reported on torsional, silicon micromachined mirrors, with a single degree of freedom. High dc voltage for static measurements, and sinusoidal or white-noise or step excitation for dynamic characterization, have been used for mirror driving.

A Chaos-Based Approach to Secure Communications

These authors describe a unique approach to safeguarding data transmission over the Internet-by embedding messages within optical chaos.