An alignment-free fiber-coupled microsphere resonator for gas sensing applications

Abstract

In this paper we report on the assembly of a robust sensor system consisting of a polystyrene microsphere resonator attached to an optical fiber taper. Since the sphere is only supported by the micrometer-sized fiber no further alignment is necessary. This results in a thermally and mechanically well isolated optical resonator system with quality factors as high as 6×105. The narrow resonances of whispering gallery modes supported by the polystyrene resonators shift with temperature at a rate of 3.8 GHz/K. Thus, a sensitive thermometer is established which allows to detect the surrounding gas via its characteristic thermal conductivity.

Fine-tuning of whispering gallery modes in on-chip silica microdisk resonators within a full spectral range

“…2. The resulting shift rate of 1.15 GHz/K agrees well with the theoretical estimation based on Gregor et al 12 For the material parameters of pure fused silica (n 1550nm…”

WGM microresonators: sensing, lasing and fundamental optics with microspheres

“…The measured wavelength shifts indicate a sensitivity range between 4.5 pm/K and 11 pm/K [102]. Thermal-based gas sensing using microspheres was developed [103] using an alignment-free fiber-coupled polystyrene microsphere resonator. The microsphere was attached to the tapered fiber coupler by electrostatic attraction only; this provided improved thermal and vibration isolation.…”

Phone-sized whispering-gallery microresonator sensing system

“…However, till now all the demonstrations were implemented in optical laboratories with well-set equipment on bulky optical tables, which limit the practical applications of WGM microresonators, e.g., various kinds of sensing, including sensing of single nanoparticle [4][5][6][7], biomolecule [21,22], magnetic field [23,24], angular velocity [25][26][27], gas [28,29], etc. The obstacles of practical applications for WGM sensors lie on two factors: i) the challenge of long-term stability for tapered fiber coupling of cavity modes outside the laboratory, and ii) bulky commercial equipment needed for testing cavity modes, including not only a laser source and a detector but also a function generator and an oscilloscope.…”