Design, preparation and characterization of novel types of optical microresonators for chemical detection

Sponsor: Czech Science Foundation

Principal investigator: Vlastimil Matějec, Ph.D.

Co-principal investigator: Prof. Ing. Václav Kubeček, DSc.

Members: Ivo Bartoň, MSc.; Daniela Berková, Ph.D.; Prof. Jiří Čtyroký, DSc.; Miloš Hayer, Ph.D.; Miroslav Chomát, Ph.D.; Ivan Kašík, Ph.D.; Ondřej Podrazký, Ph.D.; Filip Todorov, Ph.D.

From: 2009-01-01

To: 2011-12-31

The project focused on research into new types of micro-resonators for optical sensors using "whispering-gallery" (WGM) modes to detect very small changes in the external refractive index.

Spherical silica micro-resonators and "spherical" micro-resonators with circular and hexagonal cross-section were theoretically and experimentally investigated in this project. The micro-resonators with quality factor Q from 103 to 106 were prepared by heating the quartz fibers (see Fig. 1)

Fig. 1: Photo of prepared micro-resonators; A-spherical micro-resonator, Φ˜350μm, Q˜106; B-
“spherical” micro-resonator, Φ˜95μm, Q˜10³.

Fig. 2: Resonance spectrum of a spherical micro-resonator which was excited by a taper; blue curve-resonator in the air, green curve - effect of acetone vapor.

A method was developed for the excitation of WGM modes that use fiber taper with a constant diameter of less than 5 microns. To improve the selectivity of micro-resonator detection an original method of applying porous detection layers by sol-gel onto the surface of the micro-resonator was prepared. This method made it possible to detect changes in the refractive index at the level of 10-4 -10-5 caused by vapors of acetone (see Fig. 2)

References:

1. V. Matějec et al., Effect of sol-gel modifications on characteristics of silica spherical microresonators, Sensor Letters 2011, Vol. 9, pp. 2265-2267.
2. F. Todorov et al., Bottle microresonators fabricated by shaping optical fibers with a beam of a CO2 laser, Sensor Letters 2011, Vol. 9, pp. 2279-2282.