OSA-RS ANNUAL STUDENT TALKS

Every year, OSA-RS hosts two local student speakers on one night to share current research with the community.  This year, we welcome speakers from University of Rochester and Rochester Institute of Technology to give talks about optimal representation of thin-film III-V space photovoltaics and characterization of photonic integrated circuits.

Light Management in Thin-Film Gallium Arsenide Solar Cells

Julia D'Rozario, Rochester Institute of Technology

Abstract

Thin-film III-V space photovoltaics (PV) present an attractive solution for lightweight, radiation-tolerant technology as the dependence on the minority carrier diffusion length reduces with the absorber thickness. To match the current output realized in optically thick PV, light trapping structures in the form of back surface reflectors (BSR) can enhance the photogenerated current by increasing the photon path length inside the thin solar cell. This research investigates cost-effective BSRs to improve photon absorption in thin-film GaAs solar cells, produced by solution-based chemical etching and inverse progression metal-assisted chemical etching (I-MacEtch). The textured BSRs show an increased haze in reflectance compared to the planar backside reflectors, indicating a higher degree of angular photon scattering. The lifetime enhancement factor (LEF), which describes the extended photon lifetime inside the solar cell cavity due to effective light trapping, is larger in the solar cells with textured reflectors compared to the solar cell without light trapping. These outcomes correlate with the measured boost in current output from the thin-film solar cells with textured BSRs, promising for integration into space PV.

About the speaker

Julia D’Rozario is a fourth-year Ph.D. candidate working under the advisement of Dr. Seth Hubbard in the Microsystems Engineering Program at the Rochester Institute of Technology. Her dissertation research focuses on improving photon absorption using light management in thin-film III-V space photovoltaics. Her research on light management in gallium arsenide solar cells was recognized at the 46th IEEE Photovoltaic Specialists Conference in 2019, where she was granted the Best Poster Award in Area 1: Novel Architectures for Improved Opto-Electronic Performance. In 2016, Julia obtained her Bachelor of Science in Physics and Bachelor of Arts in Cinema and Screen Studies from the State University of New York at Oswego.

Polarization Characterization from Scattered Light of Photonic Integrated Circuits

Tyler Howard, University of Rochester

Abstract

Photonic integrated circuits (PICs) have become a key component in reducing the size of optical processing for information and communication applications. Using total internal reflection light is primarily contained within micron to nano-sized optical channels to route, manipulate and process light within and between PICs. However, the confinement of light within the circuit is not 100 % efficient as sidewall imperfections and defects within the substrate cause light to leak out of the guiding channel. Depending on the input polarization of the light and size of the scattering defect the polarization of light is affected to mainly emit in a certain orientation. Measuring the light scattered in this manner can yield important performance metrics useful to determine the viability of the PIC in commercial use. In this talk I will show the mechanisms for scattering in PICs, simulation tools used to numerically compute the scattered fields near the scattering source and at a microscope objective, and experimental means of measuring the polarization state of the scattered light.

About the speaker

Tyler Howard is a PhD student in Thomas Brown’s group at the Institute of Optics, investigating polarization properties of subwavelength scatters in photonic integrated circuits. He graduated from Southeast Missouri State University in May of 2019 with a double major in Physics and Engineering Physic: Mechanical Applications. He joined the University of Rochester’s PhD program for Optics in August 2019 and is in his second year in the program.