In JoVE (1)

Other Publications (3)

Articles by Tindaro Ioppolo in JoVE

Other articles by Tindaro Ioppolo on PubMed

Micro-optical Force Sensor Concept Based on Whispering Gallery Mode Resonators

Applied Optics. Jun, 2008  |  Pubmed ID: 18516120

A micro-optical force sensor concept based on the morphology-dependent shifts of optical modes of dielectric microspheres is investigated. The optical resonances, commonly referred to as the whispering gallery modes (WGM), were excited by evanescently coupling light from a tunable diode laser using a tapered single-mode fiber. A compressive force applied to the sphere induces a change in both the shape and the index of refraction of the sphere leading to a shift in WGM. By tracking the shifts, the force magnitude is determined using solid silica as well as solid and hollow Polymethyl-methacrylate (PMMA) microsphere resonators. A measurement sensitivity as high as dlambda/dF=7.664 nm/N was demonstrated with a 960 mum hollow PMMA sphere.

Tuning of Whispering Gallery Modes of Spherical Resonators Using an External Electric Field

Optics Express. Sep, 2009  |  Pubmed ID: 19770862

In this paper we investigate the electrostriction effect on the whispering gallery modes (WGM) of polymeric microspheres and the feasibility of a WGM-based microsensor for electric field measurement. The electrostriction is the elastic deformation (strain) of a dielectric material under the force exerted by an electrostatic field. The deformation is accompanied by mechanical stress which perturbs the refractive index distribution in the sphere. Both strain and stress induce a shift in the WGM of the microsphere. In the present, we develop analytical expressions for the WGM shift due to electrostriction for solid and thin-walled hollow microspheres. Our analysis indicates that detection of electric fields as small as ~500V/m may be possible using water filled, hollow solid polydimethylsiloxane (PDMS) microspheres. The electric field sensitivities for solid spheres, on the other hand, are significantly smaller. Results of experiments carried out using solid PDMS spheres agree well with the analytical prediction.

Magnetorheological Polydimethylsiloxane Micro-optical Resonator

Optics Letters. Jun, 2010  |  Pubmed ID: 20548378

We investigate the possibility of using magnetorheological polydimethylsiloxane (MR-PDMS) spheres as micro-optical resonators. In particular, the effect of a magnetic field on the whispering gallery modes (WGM) of these resonators is studied. The applied field induces mechanical deformation, causing shifts in the WGM. The microspheres are made of PDMS with embedded magnetically polarizable particles. An analysis is carried out to estimate the WGM shifts induced by an external magnetic field. An experiment is also carried out to demonstrate the magnetic field-induced WGM shifts in an MR-PDMS microsphere. The results indicate that MR-PDMS microspheres can be used as high-Q-factor tunable optical cavities with potential applications in sensing.

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