In this experimental study, which was carried out in photonics laboratory at Strathclyde University, UK, dynamics of a multi-Quantum well semiconductor active medium laser, was studied. This is in order to study its emission stability and pulse shape development under the influence of strong optical feedback level with different deriving currents, in the free space transmission medium. An external stable resonator was constructed by inserting high reflectivity dielectric mirror outside the laser output, 20 cm apart from it, which is an extralarge external cavity. Controlling the reflected back optical power was done by using a nonpolarized (50:50) beam splitter. The external resonator supported by focusing (plano-convex) lens in order to make it stable. Laser translated from stable emission when it was solitary, to quasi-static, and low fluctuated, behaves, to be coherence collapse. This is due to the strong (50%) level of optical feedback.
Studying Laser Diode Dynamics with Optical Feedback from 20cm Free Space External Resonator
Semiconductor Laser
External Cavity
Optical Feedback
Low Frequency Fluctuations
Coherence Collapse
Chaos.
Publication Date
Wed Dec 01 2021
Journal Name
Structures
The effect of ground motion characteristics on the fragility analysis of reinforced concrete frame buildings in Australia
The seismic performance of buildings can be assessed through fragility analysis as it yields the probability of the demand exceeding the capacity at a specified level of intensity. Although it's well-identified that earthquake uncertainties dominate the fragility characteristics
the influence of the characteristics of the earthquake on the fragility analysis is not well investigated. This study aims to compare the effect of earthquake characteristics on the fragility values of typical buildings in Australia. To achieve this
a typical reinforced concrete building is selected and modeled using a finite element approach. Various ground motion suites
such as near-fault
far-fault
and long-duration are selected
and the fragility analysis has been carried out for each ground motion suite. It is observed that the variation in the median values of the collapse fragilities can be as high as 48% between short-duration and long-duration ground motions
and about 40% between long-duration and pulse-like ground motions.
(2)
