Microcavity morphology optimization

Abstract

High spectral mode density of conventional optical cavities is detrimental to the generation of broad optical frequency combs and to other linear and nonlinear applications. In this work we optimize the morphology of high-Q whispering gallery (WG) and Fabry-Perot (FP) cavities and find a set of parameters that allows treating them, essentially, as single-mode structures, thus removing limitations associated with a high density of cavity mode spectra. We show that both single-mode WGs and single-mode FP cavities have similar physical properties, in spite of their different loss mechanisms. The morphology optimization does not lead to a reduction of quality factors of modes belonging to the basic family. We study the parameter space numerically and find the region where the highest possible Q factor of the cavity modes can be realized while just having a single bound state in the cavity. The value of the Q factor is comparable with that achieved in conventional cavities. The proposed cavity structures will be beneficial for generation of octave spanning coherent frequency combs and will prevent undesirable effects of parametric instability in laser gravitational wave detectors.

Transverse-mode coupling and diffraction loss in tunable Fabry–Pérot microcavities

“…The calculations provide improved accuracy for the determination of emitter-cavity coupling strength as well as detailed information about possible sample-induced scattering and loss. Finally, the approach offers an efficient route for the design of novel cavity geometries with non-trivial properties, such as single-transverse-mode operation [33,34], where higher order modes can be suppressed without significantly affecting the fundamental mode e.g.to improve spectral filtering, or mode imaging [35], where a cavity mode is designed to avoid a scatterer to reduce loss. This opens the potential for light modes to be individually tailored for specific applications.…”

Microscopic optical buffering in a harmonic potential

“…The nanoscale variation of the surface height of SNAP resonators is generally axially asymmetric. For resonators with axial dimensions of several microns and height variation of a few micrometres, the asymmetry may reduce the Q-factor and eventually destroy the resonator 28 29 . However, for the SNAP resonators of our interest having the axial length of the order of 100 μm or greater and height of several nanometres, this effect is small 29 .…”

On fundamental diffraction limitation of finesse of a Fabry–Perot cavity

“…Practical applications of FP cavities with non-spherical mirrors [5][6][7] often call for an evaluation of the stability of the cavity with respect to small tilt of the mirrors [20,21,33,34]. A direct simulation of the cavity with tilted mirror is hindered by the asymmetrical morphology of the system.…”