Retroreflector array as a tapped delay-line filter for ultra-short optical pulses

A retroreflector array can be used to act as an optical tapped delay-line filter for temporal optical signals. Here, we demonstrate the basic operation and present a theoretical description. Our theory is based on the mathematical formalism for finite impulse response filters. A relationship to the classical Talbot bands experiment is established. By adding a mask to the retroreflector array, one can implement arbitrary filter operations. As a specific example, a differentiation in frequency domain is demonstrated by using a simple binary mask. The proposed devise maybe useful for the optical filtering and shaping of ultra short pulses

Investigating Optical Properties of One-Dimensional Photonic Crystals Containing Semiconductor Quantum Wells

This study examined MQWs made of InGaAs/GaAs, InAlAs/InP, and InGaAs/InP in terms of their band structure and reflectivity. We also demonstrated that the reflectivity of MQWs under normal incident was at maximum, while both using a strong pump and changing incident angle reduced it. Reflectivity of the structure for a weak probe pulse depends on polarization, intensity of the pump pulse, and delay between the probe pulse and the pump pulse. So this system can be used as an ultrafast all-optical switch which is inspected by the transfer matrix method. After studying the band structure of the one-dimensional photonic crystal, the optical stark effect (OSE) was considered on it. Due to the OSE on virtual exciton levels, the switching time can be in the order of picoseconds. Moreover, it is demonstrated that, by introducing errors in width of barrier and well as well as by inserting defect, the reflectivity is reduced. Thus, by employing the mechanism of stark effect MQWs band-gaps can be easily controlled which is useful in designing MWQ based optical switches and filters. By comparing the results, we observe that the reflectivity of MWQ containing 200 periods of InAlAs/InP quantum wells shows the maximum reflectivity of 96%