Bespoke mirror fabrication for quantum simulation with light in open-access microcavities

Abstract

In this work, we use focused ion beam (FIB) milling to generate custom mirror shapes for quantum simulation in optical microcavities. In the paraxial limit, light in multimode optical microcavities follows an equation of motion which is equivalent to Schrödinger’s equation, with the surface topography of the mirrors playing the role of the potential energy landscape. FIB milling allows us to engineer a wide variety of trapping potentials for microcavity light, through exquisite control over the mirror topography, including 2D box, 1D waveguide, and Mexican hat potentials. The 2D box potentials are sufficiently flat over tens of microns, that the optical modes of the cavity, found by solving Schrödinger’s equation on the measured cavity topography, are standing-wave modes of the box, rather than localised to deviations. The predicted scattering loss due to surface roughness measured using atomic force microscopy is found to be 177 parts per million, which corresponds to a cavity finesse of 2.2 × 104 once other losses have been taken into account. Spectra from dye-filled microcavities formed using these features show thermalised light in flat 2D potentials close to dye resonance, and spectrally-resolved cavity modes at the predicted frequencies for elliptical potentials. These results also represent a first step towards realising superfluid light and quantum simulation in arbitrary-shaped optical microcavities using FIB milling.

Transport and localization of light inside a dye-filled microcavity

“…The structure and dimension of either the biased or disordered, random lattice poten-tials, as sketched in Fig. 1(b), can be fabricated with minute precision on the transverse space of the cavity mirrors [48]. Further, the thermalization conditions can be controlled by tuning the cutoff frequency of the microcavity for a specific photon loss rate.…”

“…Here, we consider a transverse potential landscape consisting of a one-dimensional (1D) lattice of square well potentials. This can be realized by fabricating quasi 1D potentials on the planar substrate of dielectric mirrors using focussed ion beam milling [46][47][48] (see Fig. 1).…”

Compressibility and the Equation of State of an Optical Quantum Gas in a Box

“…[22] for a detailed description of the method. We note that recent other work has reported an alternative technique to create potentials for microcavity photon gases, including box potentials, using focused ion beam milling [34]. In our work, the mirrors used as writing samples contain a 30 nm-thin silicon layer below their dielectric Bragg coating, which enables the structuring process: A 532 nm laser beam is focused through the quartz glass substrate onto the silicon layer (beam diameter 1 µm), where part of the light is absorbed and converted into heat.…”

Optimisation of Scalable Ion-Cavity Interfaces for Quantum Photonic Networks

“…We now consider an alternative cut through this parameter space, to gain insight into the trade-offs involved in the fabrication of the mirror substrate. The difficulty of high-quality micromirror fabrication tends to increase with both the volume of material removed (V cap ) and the maximum surface angle (β cap ) of the resulting concave form [50]. Both quantities increase with increasing mirror diameter and decreasing radius of curvature, so we now consider the impact on P ext of varying the limits on these two parameters.…”