Ultra high-Q WGM microspheres from ZBLAN for the mid-IR band

TL;DR

This paper reports the development of high-Q ZBLAN microspheres for mid-IR photonics, achieving record quality factors exceeding 10^8, enabling advanced mid-IR device applications.

Contribution

It introduces a novel fabrication method for ZBLAN microspheres with high Q-factors in the mid-IR range, surpassing previous material limitations.

Findings

Intrinsic Q-factor at telecom wavelength is (5.4±0.4)×10^8.

Record Q-factor in mid-IR exceeds 10^8.

Effective excitation of whispering gallery modes demonstrated.

Abstract

The advantages of high-quality-factor whispering gallery mode microresonators can be applied to develop novel photonic devices for the mid-IR range. ZBLAN (glass based on heavy metal fluorides) is one of the most promising materials to be used for this purpose due to low optical losses in the mid-IR. We developed original fabrication method based on melting of commercially available ZBLAN-based optical fiber to produce high-Q ZBLAN microspheres with the diameters of 250 to 350 $\mu$m. We effectively excited whispering gallery modes in these microspheres and demonstrated high quality factor both at 1.55 $\mu$m and 2.64 $\mu$m. Intrinsic quality factor at telecom wavelength was shown $(5.4\pm0.4)\cdot10^8$ which is defined by the material losses in ZBLAN. In the mid-IR at 2.64 $\mu$m we demonstrated record quality factor in ZBLAN exceeding $10^8$ which is comparable to the highest values of the Q-factor among all materials in the mid-IR.