Date of Award

2026

Document Type

Honors Thesis (Open Access)

Department

Colby College. Physics and Astronomy Dept.

Advisor(s)

Duncan Tate

Abstract

This thesis describes an experimental exploration of electromagnetically induced transparency (EIT) in atoms of 85Rb using a new MOGLabs external cavity diode laser. A two-step ladder technique of EIT was applied using a 5S_1/2→5P_3/2 probe transition and 5P_3/2→nD_5/2 coupling transitions. Significant apparatus tuning was done, including developing a reliable procedure of regulating frequency and scanning the coupling laser over a sufficient mode-hop free range. A Doppler-reduced technique was applied by counter-propagating the probe and coupling beams through the Rb vapor cell. EIT signals were collected at various probe and coupling laser powers to analyze changes in signal size and linewidth. Analyzed data was collected around the n=41 Rydberg state. Signal analysis was performed by fitting Lorentzian curves to observed peaks. Results revealed signal size increased nearly linearly with probe and coupling laser power, while linewidth remained nearly constant for both. Increasing signal size was expected for varying probe and coupling laser powers. Constant linewidth was not expected for varying probe or coupling laser power due to the effects of power broadening, especially for the probe. Average signal linewidths were broader than expected, ranging from 50-68 MHz, and peak shapes appeared to have non-Lorentzian features. These unexpected behaviors led to the conclusion that alternative sources of broadening were influencing the apparatus. Potential sources include suboptimal beam alignment, laser jitter, and unresolved Zeeman splittings due to stray magnetic fields. Further optimization of peak widths will allow application of the MOGLabs laser for probing higher energy Rydberg states.

Keywords

Electromagnetically Induced Transparency, Rydberg Atoms, External Cavity Diode Laser, Optical Instrumentation, Mode-Hop Free Scanning, Lorentzian Fitting Analysis

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Click below to download supplemental content.

Two-StepRydbergEITSetup2025_26.pdf (4452 kB)
EITLinewidthandSizeAnalysis.ipynb (8617 kB)
T0020.CSV (161 kB)

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