A. Pérez-Serrano

Modal structure, directional and wavelength jumps of integrated semiconductor ring lasers: Experiment and theory

We have experimentally and theoretically analyzed the modal properties of semiconductor ring lasers and the wavelength jumps that occur in connection with directional switching above the threshold.

Longitudinal mode multistability in Ring and Fabry-Pérot lasers: the effect of spatial hole burning

We theoretically discuss the impact of the cavity configuration on the possible longitudinal mode multistability in homogeneously broadened lasers. Our analysis is based on the most general form of a Travelling-Wave Model for which we present a method that allows us to evaluate the monochromatic solutions as well as their eigenvalue spectrum. We find, in agreement with recent experimental reports, that multistability is more easily reached in Ring than in Fabry-Pérot cavities which we attribute to the different amount of Spatial-Hole Burning in each configuration.

Semiconductor snail lasers

A modified ring laser geometry is presented to promote stable unidirectional lasing. The effects of directional coupling and facet reflectivities are investigated with respect to quantum efficiency, directionality, and side-mode suppression ratio of the lasing spectra. Simulation and experimental results are presented showing single mode (>20 dB side-mode suppression ratio), unidirectional lasing on an InP based multiple quantum well material.

Delay algebraic equations for broad area lasers

We discuss an efficient modeling approach for the simulation of broad area laser diodes. Our method is based on folding the longitudinal propagation dimension into time delays. We compare the results of the dynamics obtained with our improved model with the results of a standard traveling wave description in the cases of straight current stripes and tapered anti-reflection coated devices. We obtain an excellent agreement and an improvement of the integration time between one and two orders of magnitudes.

Bifurcation analysis of traveling wave models

We present a general method allowing to perform a direct bifurcation diagram and to determine the stability of the solutions of a Traveling wave model. We exemplify the cases of the two level atom and the semiconductor quantum well lasers.

Wavelength multistability in ring and fabry-Pérot lasers: The effect of spatial hole burning

Recently it was experimentally demonstrated [1,2] that the emission wavelength of bidirectional semiconductor ring lasers (SRLs) can be selected by optical injection at wavelengths corresponding to the modes of the cavity; upon removal of the optical injection, the emission wavelength remains stable at the chosen value. It was found that this multistability can coexist with the directional bistability shown by these devices, therefore it can be of interest for all-optical signal processing applications at higher-logical level [3]. On the other hand, this multistability has, to our knowledge, never been explained or reported in Fabry-Pérot (FP) lasers, hence it recalls for an explanation of the different behavior shown by ring RLs and FP lasers regarding multistability.

Modal structure of integrated Semiconductor Ring Lasers with output waveguides

In recent years Semiconductor Ring Lasers (SRLs) have attracted interest for their diverse potential application, e.g. their fast directional bistability recently opened up a new scenario for the development of all-optical memories and signal processing [1]. Besides, SRLs show unexpected dynamical behaviors, such as hysteresis in the lasing direction [2], and peculiar lasing mode selection rules [3]. In this contribution, we present an experimental and theoretical investigation concerning the modal structure and selection rules of a SRL with output waveguides.

Semiconductor Snail Laser

A key advantage that semiconductor ring lasers have over Fabry-Pérot (FP) devices for relatively high power applications, is that they do not suffer from Catastrophic Optical Damage (COD) to the cleaved facets of the device bar[1]. However, the directional coupler (DC) section in the ring geometry, equivalent to the facet conditions in a FP laser, cannot be modulated as easily as the FP facets to provide the equivalent to high and low reflectivity coatings, that allow increased quantum efficiency. The symmetric nature of the coupling in ring lasers produces both bidirectional or (fluctuating) bistable directional lasing of the device[2]. In order to produce unidirectional, stable lasing in ring lasers a snail geometry, as shown in Fig.2(a), is considered here. In this case the laser has one cleaved output facet, and the input waveguide is curved until it couples with itself. The benefit is that low coupling between the waveguides in the DC may be easily designed, where the normal ring and bus waveguide geometry equivalent, requiring high coupling values, is more sensitive to fabrication tolerances, and requires long interaction lengths, increasing the device footprint. As a theoretical result, we have calculated the fundamental mode thresholds and output power for Semiconductor Snail Laser (SSL) as a function of device parameters, i.e. coupler efficiency and output facets reflectivities. The coupler efficiency (δ) is the fraction of light transmitted between the waveguides in the DC. We have used a scattering matrix formulation and an analytical approximation to the optical susceptibility for the medium description [3], in order to determine the “optimal” coupling efficiency that maximizes the output power (see Fig.1.) Lasing action and good emission properties were therefore theoretically predicted.

Modal structure of integrated semiconductor ring lasers with output waveguides

We have experimentally and theoretically analyzed the modal properties of semiconductor ring lasers and the wavelength jumps that occur in connection with directional switching above threshold.