Ultrashort Q-switched pulses from a passively mode-locked distributed Bragg reflector semiconductor laser

A compact semiconductor mode-locked laser (MLL) is presented that demonstrates strong passive Q-switched mode-locking over a wide range of drive conditions. The Q-switched frequency is tunable between 1 and 4 GHz for mode-locked pulses widths around 3.5 ps. The maximum ratio of peak to average power of the pulse-train is >120, greatly exceeding that of similarly sized passively MLLs

Semiconductor snail laser

A new snail laser geometry is modelled and presented, exhibiting stable, unidirectional lasing at both 1550 nm and 808 nm. 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 is the fraction of light transmitted between the waveguides in the directional couplers (DC). We have used a scattering matrix formulation and an analytical approximation to the optical susceptibility for the medium description, in order to determine the "optimal" coupling efficiency that maximizes the output power. Lasing action and good emission properties were therefore theoretically predicted

Approaches to modelling land erodibility by wind

Land susceptibility to wind erosion is governed by complex multiscale interactions between soil erodibility and non-erodible roughness elements populating the land surface. Numerous wind erosion modelling systems have been developed to quantify soil loss and dust emissions at the field, regional and global scales. All of these models require some component that defines the susceptibility of the land surface to erosion, ie, land erodibility. The approaches taken to characterizing land erodibility have advanced through time, following developments in empirical and process-based research into erosion mechanics, and the growing availability of moderate to high-resolution spatial data that can be used as model inputs. Most importantly, the performance of individual models is highly dependent on the means by which soil erodibility and surface roughness effects are represented in their land erodibility characterizations. This paper presents a systematic review of a selection of wind erosion models developed over the last 50 years. The review evaluates how land erodibility has been modelled at different spatial and temporal scales, and in doing this the paper identifies concepts behind parameterizations of land erodibility, trends in model development, and recent progress in the representation of soil, vegetation and land management effects on the susceptibility of landscapes to wind erosion. The paper provides a synthesis of the capabilities of the models in assessing dynamic patterns of land erodibility change, and concludes by identifying key areas that require research attention to enhance our capacity to achieve this task