Imperial College London


Faculty of EngineeringDepartment of Materials

Reader in Functional Microwave Materials & Devices



+44 (0)20 7594 1410m.oxborrow




2.04Royal School of MinesSouth Kensington Campus






BibTex format

author = {Oxborrow, M and Bourgeois, P-Y and Kersalé, Y and Giordano, V},
title = {DC-powered Fe3+:sapphire Maser and its Sensitivity to Ultraviolet Light},
url = {},
year = {2010}

RIS format (EndNote, RefMan)

AB - The zero-field Fe3+:sapphire whispering-gallery-mode maser oscillatorexhibits several alluring features: Its output is many orders of magnitudebrighter than that of an active hydrogen maser and thus far less degraded byspontaneous-emission (Schawlow-Townes) and/or receiving-amplifier noise. Itsoscillator loop is confined to a piece of mono-crystalline rock bolted into ametal can. Its quiet amplification combined with high resonator Q provide theingredients for exceptionally low phase noise. We here concentrate on noveltiesaddressing the fundamental conundrums and technical challenges that impedeprogress. (1) Roasting: The "mase-ability" of sapphire depends significantly onthe chemical conditions under which it is grown and heat-treated. We providesome fresh details and nuances here. (2) Simplification: This paper obviatesthe need for a Ka-band synthesizer: it describes how a 31.3 GHz looposcillator, operating on the preferred WG pump mode, incorporating Poundlocking, was built from low-cost components. (3) "Dark Matter": A Siegman-levelanalysis of the experimental data determines the substitutional concentrationof Fe3+ in HEMEX to be less than a part per billion prior to roasting and up toa few hundred ppb afterwards. Chemical assays, using different techniques(incl. glow discharge mass spectra spectroscopy and neutron activationanalysis) consistently indicate, however, that HEMEX contains iron atconcentrations of a few parts per million. Drawing from severalforgotten-about/under-appreciated papers, this substantial discrepancy isaddressed. (4) Excitons: Towards providing a new means of controlling theFe3+:sapph. system, a cryogenic sapphire ring was illuminated, whilst masing,with UV light at wavelengths corresponding to known electronic andcharge-transfer (thus valence-altering) transitions. Preliminary experimentsare reported.
AU - Oxborrow,M
AU - Bourgeois,P-Y
AU - Kersalé,Y
AU - Giordano,V
PY - 2010///
TI - DC-powered Fe3+:sapphire Maser and its Sensitivity to Ultraviolet Light
UR -
ER -