Pre-distortion adaptive optics for optical feeder links: simulations and performance analyses.

Optical feeder links offer immense utility in meeting future communication demands-however, atmospheric turbulence limits their performance. This work targets this challenge through analyses of a bidirectional free-space optical communication (FSOC) link that incorporates pre-distortion adaptive optics (AO) between the next-generation optical ground station at the German Aerospace Center (DLR) Oberpfaffenhofen and the laser communications terminal on Alphasat-a satellite in geostationary orbit (GEO). The analyses are performed via end-to-end Monte Carlo simulations that provide realistic performance estimates of the bidirectional FSOC link for a GEO feeder link scenario.

Manifestations of Laser-Induced Graphene under Ultraviolet Irradiation of Polyimide with Varied Optical Fluence.

In this work, we put forward a rigorous study on ultraviolet (355-nm) laser irradiation of polyimide for the realization of high-quality laser-induced graphene (LIG) with micron-scale features. High-quality material and micron-scale features are desirable-but often at odds-given that small features demand tightly focused beam spots, with a predisposition to ablation. As such, we investigate the synthesis of LIG by correlating the material characteristics, as gleaned from scanning electron microscopy and Raman spectroscopy, to the incident optical fluence, as a measure of applied optical energy per unit area.

All-optical retro-modulation for free-space optical communication.

This work presents device and system architectures for free-space optical and optical wireless communication at high data rates over multidirectional links. This is particularly important for all-optical networks, with high data rates, low latencies, and network protocol transparency, and for asymmetrical networks, with multidirectional links from one transceiver to multiple distributed transceivers. These two goals can be met by implementing a passive uplink via all-optical retro-modulation (AORM), which harnesses the optical power from an active downlink to form a passive uplink through retroreflection.

Photoconductive terahertz generation from textured semiconductor materials.

Photoconductive (PC) terahertz (THz) emitters are often limited by ohmic loss and Joule heating-as these effects can lead to thermal runaway and premature device breakdown. To address this, the proposed work introduces PC THz emitters based on textured InP materials. The enhanced surface recombination and decreased charge-carrier lifetimes of the textured InP materials reduce residual photocurrents, following the picosecond THz waveform generation, and this diminishes Joule heating in the emitters.