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We present an experimental study of the stability of passively mode-locked pulses against noise in multipulse operation of an erbium-doped fiber laser. The laser properties are determined by two dimensionless combinations of the laser parameters. Measurements of the pulses' destabilization threshold as a function of those laser parameters show the optimal regions that maximize the mode-locked pulse stability. We find good agreement between the experimental observations and the theoretical predictions.

We demonstrate experimentally an optical system for undersampling several bandwidth-limited signals with carrier frequencies that are not known apriori and can be located within a broad frequency region of 0-20 GHz. The system is based on undersampling synchronously at three different rates. The optical undersampling down-converts the entire system bandwidth into a low frequency region called baseband. The synchronous sampling at several rates enables to accurately reconstruct signals even in cases in which different signals overlap in the baseband region of all sampling channels. Reconstruction of three simultaneously generated chirped signals, each with a bandwidth of about 200 MHz, was experimentally demonstrated.

We experimentally demonstrate critical behavior of a passively mode-locked laser with properties that are similar to those of gas-liquid and magnetic spin systems. The laser light modes provide a special nonthermodynamic many-body system where noise takes the role of temperature. It is also a rare opportunity of an experimental pure one-dimensional system. As theoretically predicted, we identified in the laser light-mode system two thermodynamiclike phases, one characterized by spontaneous pulses and the second by field-induced parapulses, separated by a first order phase transition boundary that is terminated by the critical point. We also measured the critical exponents, β≈0.52, γ≈1, and δ≈3.1, which are close to the mean field values that are exact in the laser system.

We demonstrate a simple method for complete characterization (of amplitudes and phases) of short optical pulses, using only a dispersive delay line and an oscilloscope. The technique is based on using a dispersive delay line to stretch the pulses and recording the temporal interference of two delayed replicas of the pulse train. Then, by transforming the time domain interference measurements to spectral interferometry, the spectral intensity and phase of the input pulses are reconstructed, using a Fourier-transform algorithm. In the experimental demonstration, mode-locked fiber laser pulses with durations of approximately 1 ps were characterized with a conventional fast photodetector and an oscilloscope.

We present an experimental study of the probabilistic nature of pulsation self-starting in passively mode-locked lasers. It is a Poissonian process that results from a noise-activated switching barrier. The switching rate from cw operation to pulsation when the laser pump level is turned on has an exponential dependence that is inversely proportional to the square of the laser power.

A simple and practical microwave frequency-shifting technique based on a general temporal self-imaging (GTSI) effect in optical fiber is proposed, formulated, and experimentally demonstrated. The proposed technique can be applied to an arbitrary periodic microwave signal (e.g., a microwave tone) and provides unparalleled design flexibility to increase the frequency of the input microwave signal up to the desired value (limited only by the photodetector's bandwidth). For instance, we demonstrate frequency upshifting of microwave tones from approximately 10 to approximately 50 GHz and from approximately 40 to approximately 354 GHz. These results also represent what is to the authors' knowledge the first experimental observation of GTSI phenomena.

We present a theoretical and experimental study of multiple pulse formation in passively mode-locked lasers. Following a statistical-mechanics approach, the study yields a thermodynamic-like "phase diagram" with boundaries representing cascaded first order phase transitions. They correspond to abrupt creation or annihilation of pulses and a quantized rf power behavior, as system parameters (noise and/or pumping levels) are varied, in excellent accordance with the experiments. Remarkably, individual pulses carry an almost constant quantum of energy.