Towards a compact optical fibre clock

We have loaded a hollow core photonic crystal fibre (HC-PCF) with
¹²⁷
I
₂
and used it to record an absorption spectrum of iodine near 532 nm. We will measure the hyperfine structures of the P142 (37-0) transition of
¹²⁷
I
₂
in a HC-PCF and compare it to measurements made using a traditional
¹²⁷
I
₂
gas cell to determine how much spectral line broadening is induced in the HC-PCF as a result of gas particle collisions with the walls of the fibre. We aim to provide an estimate of the stability obtainable in a clock based on an
¹²⁷
I
₂
loaded HCPCF.