Fundamental limit of microresonator field uniformity and slow light enabled ultraprecise displacement metrology

M. Sumetsky*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review


We determine the fundamental limit of microresonator field uniformity. It can be achieved in a specially designed microresonator, called a bat microresonator, fabricated at the optical fiber surface. We show that the relative nonuniformity of an eigenmode amplitude along the axial length L of an ideal bat microresonator cannot be smaller than 31 π 2 n4 λ−4 Q−2 L4, where n, λ, and Q are its refractive index, eigenmode wavelength, and Q-factor, respectively. For a silica microresonator with Q = 108, this eigenmode has axial speed ∼ 10−4 c, where c is the speed of light in vacuum, and its nonuniformity along length L = 100 µm at wavelength λ = 1.5 µm is ∼ 10−7. For a realistic fiber with diameter 100 µm and surface roughness 0.2 nm, the smallest eigenmode nonuniformity is ∼ 0.0003. As an application, we consider a bat microresonator evanescently coupled to high Q-factor silica microspheres, which serves as a reference supporting ultraprecise straight-line translation.

Original languageEnglish
Pages (from-to)1656-1659
Number of pages4
JournalOptics Letters
Issue number7
Early online date4 Mar 2021
Publication statusPublished - 23 Mar 2021

Bibliographical note

Funding Information:
Wolfson Foundation (22069); Engineering and Physical Sciences Research Council (EP/P006183/1).

This paper was published in Optics Letters and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law.


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