Experimental verification of enhanced photon bunching from a saturable absorber

Preliminary results of measurements of the second order correlation function g⁽²⁾ (0) of light transmitted through a saturable absorber are presented.     

Possibility of observing enhanced photon bunching from two photon emission

Two photon emission into a vacuum is shown to produce a field with a second order correlation functioning g⁽²⁾ greater than two. This offers the possibility of observing an enhanced Hanbury Brown Twiss effect from two photon spontaneous emission.     

Excitability in a semiconductor laser with saturable absorber

We show that a monolithic and compact vertical cavity laser with intracavity saturable absorber can emit short excitable pulses. These calibrated optical pulses can be excited as a response to an input perturbation whose amplitude is above a certain threshold. Subnanosecond excitable response is promising for applications to novel all-optical devices for information processing or logical gates.     

Stochastic resonance in a laser with saturable absorber

Summary We have investigated, experimentally and theoretically, the occurrence of stochastic resonance (SR) in a laser with saturable absorber: a non-linear optical system presenting optical bistability and self-pulsed regimes for the laser output intensity. In the optical-bistability regime we have obtained an excellent demonstration of SR by studying Fourier spectra and residence time distributions; operating just below the Hopf bifurcation that originates pulsed periodic regime we have obtained experimental evidence of the SR phenomenon. For operation close to the Hopf bifurcation, the theoretical analysis (performed through numerical simulations) has demonstrated that simultaneous presence of noise and periodic forcing generates excursions far from equilibrium; from the locking between these excursions and periodic forcing the SR phenomenon may arise. Paper presented at the International Workshop “Fluctuations in Physics and Biology: Stochastic Resonance, Signal Processing and Related Phenomena”, Elba, 5–10 June 1994.     

Self-pulsing localized structures in a laser with saturable absorber

We consider a broad area heterostructured semiconductor laser with an integrated saturable absorber in a monolithic configuration. We extend beyond the single-longitudinal mode approximation a model already used to predict transversely localized structures or cavity solitons (CSs) in a shorter device and we numerically demonstrate the existence of self-pulsing transverse localized structures. Like CSs, these structures can simultaneously coexist in different transverse locations.     

Phase transition analogies in a laser with saturable absorber

The possible threshold behaviours of a four-level laser in the presence of an saturable absorber are examined. In the parameter space of the absorber the regions where the threshold behaviours resemble first or second order phase transitions are found. The analysis is based on the semi-classical approximation and makes use of some concepts taken from Thom's theory of catastrophes.     

Bifurcation phenomena in a laser with saturable absorber I

We investigate the bifurcation diagram of a laser with saturable absorber in the low and medium intensity regimes. The linear stability of the stationary solutions corresponding to these regimes is studied. In the low intensity domain, a Hopf bifurcation point is determined from which a time-periodic solution emerges. This solution is contructed and its stability is analyzed in the vicinity of the bifurcation point. It is shown that this time-periodic solution is stable in a finite domain of the parameter space.     

Beam coupling induced transparency in a bacteriorhodopsin-based saturable absorber

The nonlinear coupling of two beams in a saturable absorber is shown to cause a strong enhancement of the beams' transmissivity. An analysis of this beam-coupling effect and its experimental demonstration with bacteriorhodopsin are given.     

Nonlinear focusing of femtosecond pulses as a result of self-reflection from a saturable absorber

We calculate the spatiotemporal evolution of intense, femtosecond pulses that are incident upon a saturable absorbing interface in the regime of self-reflection, using the finite-difference time-domain computational method. The pulses induce a curved, moving absorption front in the nonlinear medium that acts as a transient focusing mirror for the reflected pulse energy.     

Steady-state mode-locking operation in a laser with a saturable absorber

It is shown that a simple correspondence exists between the form of radiation for a steady-state mode-locking operation and the well-known solution of the one-mode problem. The dependence of the amplitude and shape of the pulses on the amount of absorber is determined.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, Vol. 15, No. 2, pp. 221–226, February, 1972.     

Lasers with saturable absorber driven by a coherent field

We derive the semiclassical equations governing the response of a solid-state monochromatic laser with saturable absorber driven by an external coherent field. The behavior of the emitted field intensity versus either the driving field intensity or the pump parameter of the amplifying atoms displays the same qualitative behavior. Three possible situations can appear, depending on the values taken by the relevant parameters: for a given external field intensity or pump parameter there can be one, two or three stable values of the emitted field intensity. In this way we have an example of a system which displays mono-, bi- or tristability.Chercheur Qualifié F.N.R.S.     

High-energy saturable absorber mode-locked fiber laser system

We demonstrate a mode-locked erbium-doped fiber laser with a 1-microm InGaAs saturable absorber that produces 84-ps, 1-nJ transform-limited pulses. Measurements of the InGaAs multiple quantum well revealed a slow saturable absorber that is useful for passive mode locking. Optical fiber was added to extend the cavity and vary the repetition rate from 51 kHz to 5.4 MHz. The narrow spectral width of the laser output (<0.04 nm) permits amplification to 0.2 microJ/pulse with minimal pulse broadening. Pulse energies as large as 1.7 microJ can be achieved with pulse widths of <330 ps. Average powers of 0.5 W at megahertz repetition rates are demonstrated.     

Ultrafast spectroscopy of semiconductor saturable absorber mirror

Ultrafast spectroscopy of semiconductor saturable absorber mirror(SESAM) is measured using a femtosecond pump-probe experiment.This allows dynamic responses of SESAM in the cavity to be concluded by ultrafast spectroscopy.Change in reflection is measured as a function of pump-probe delay for different pump excitation fluences.Change of nonlinear reflection of SESAM is measured as a function of incident light energy density.When the excitation fluence increases,nonlinear change in ultrafast spectroscopy of SESAM becomes increasingly significant.When SESAM is pumped by an ultrahigh excitation fluence,the energy density of which is approximately 1400 μJ/cm2,two-photon absorption can be observed visibly in its ultrafast spectroscopy.     

Small-scale instability of a pulse front traversing a resonant saturable absorber

Wave front of a light pulse is shown to be unstable as it propagates through a resonant saturable absorber, if its frequency is higher than the resonance frequency of the absorber. When ΔωT ₂∼1, a small-scale transverse instability with the dimension of (λl _abs)^1/2 grows rapidly. Its growth-rate is of the order of the small-signal-absorption length of the medium.     

2R regeneration study in a microcavity with a saturable absorber

We theoretically study the dynamical response of a saturable absorber (SA) in a microcavity realizing a non-linear mirror (NLM). We compare the effects of the SA response time on the extinction ratio of a single pulse crossing a single NLM and a two NLM based device. We also study 2R regeneration of a 40 Gbit/s pulses train with a single NLM.     

Bifurcation of periodic solutions in a laser with saturable absorber

We investigate a Hopf bifurcation at complex conjugate double eigenvalues in semiclassical equations of a laser with saturable absorber where the degeneracy of eigenvalues is implied by a symmetry. The bifurcation analysis is undertaken within a more general system of nonlinear ordinary differential equations invariant under the same transformations as laser equations. It is proved that three periodic solutions exist and their stability criteria are found.     

A saturable absorber for the iodine laser

An absorber for iodine laser pulses has been developed using iodine atoms in the ground state as the absorbing species. The iodine atoms have been produced by dissociation of gaseous molecular iodine in a heated cell. The absorption is easily saturated at moderate energy densities.