Monitored wet-etch removal of individual dielectric layers from high-finesse Bragg mirrors

Abstract

It is prohibitively expensive to deposit customized dielectric coatings on individual optics. One solution is to batch-coat many optics with extra dielectric layers, then remove layers from individual optics as needed. Here we present a low-cost, single-step, monitored wet etch technique for reliably removing (or partially removing) individual SiO${}_2$ and Ta${}_2$O${}_5$ dielectric layers, in this case from a high-reflectivity fiber mirror. By immersing in acid and monitoring off-band reflected light, we show it is straightforward to iteratively (or continuously) remove six bilayers. At each stage, we characterize the coating performance with a Fabry-Pérot cavity, observing the expected stepwise decrease in finesse from 92,000$\pm$3,000 to 3,950$\pm$50, finding no evidence of added optical losses. The etch also removes the fiber's sidewall coating after a single bilayer, and, after six bilayers, confines the remaining coating to a $\sim$50-$\mu$m-diameter pedestal at the center of the fiber tip. Vapor etching above the solution produces a tapered "pool cue" cladding profile, reducing the fiber diameter (nominally 125 $\mu$m) to $\sim$100 $\mu$m at an angle of $\sim$0.3${}^{\circ }$ near the tip. Finally, we note that the data generated by this technique provides a sensitive estimate of the layers' optical depths. This technique could be readily adapted to free-space optics and other coatings.

arXiv comment8 pages, 3 figures

References in corpus (10)

• Observation of Gravitational Waves from a Binary Black Hole Merger
• Cavity Optomechanics
• Cavity-based quantum networks with single atoms and optical photons
• Fiber Fabry-Perot cavity with high finesse
• The warm ionized medium in spiral galaxies
• Deterministic enhancement of coherent photon generation from a nitrogen-vacancy center in ultrapure diamond
• A Fabry-Perot Microcavity for Diamond-Based Photonics
• Transverse-mode coupling and diffraction loss in tunable Fabry-Pérot microcavities
• From membrane-in-the-middle to mirror-in-the-middle with a high-reflectivity sub-wavelength grating
• Integrating cavity quantum electrodynamics and ultracold-atom chips with on-chip dielectric mirrors and temperature stabilization