When fringe meets finesse : compact iodine stabilized lasers in two colour length interferometry

Abstract

This master's thesis focuses on developing a feedback loop system for stabilizing semiconductor lasers to low-pressure iodine gas absorption spectra. The goal is to generate stable wavelengths at 531 𝑛𝑚 and 688 𝑛𝑚, essential for precise two-colour length measurement interferometry in laboratories.

Semiconductor lasers are versatile light sources with broad applications in telecommunications and scientific instrumentation. However, for accurate length measurement interferometry, a stable wavelength source is vital. The thesis proposes a feedback loop system that achieves relative frequency stability levels of 10^9 by utilizing low-pressure iodine gas absorption spectra to stabilize the lasers.

The research involves creating a compact device using commercially available diode lasers and short iodine cells, resulting in a footprint of 15 𝑐𝑚 𝑥 15 𝑐𝑚 𝑥 10 𝑐𝑚 . Experimental evaluations demonstrate an uncertainty of 3 𝑀𝐻𝑧, a relative frequency stability in the order of 10^9 for both the green and red lasers with an Allan deviation in the order of 10^10 and 10^9 for the green and red lasers, respectively, making the system suitable for practical applications, including gauge block measurements.

This work contributes to the advancement of two-colour length measurement interferometry by providing a compact and stable wavelength generation system. The research opens up possibilities for enhanced accuracy and reliability in scientific and industrial applications.