Tuning of optical resonances in asymmetric microtube cavities

Abstract

We tune optical resonances in rolled-up SiO/SiO(2) microtube cavities by gradually modifying the tube structure through asymmetrical postdeposition of SiO(2). Spectral blueshifts followed by redshifts of the resonant modes are observed in a thin-walled microtube (tube-I), which is attributed to a competition between shape deformation and effective increase of tube wall thickness. In contrast, only a monotonic redshift is detected when asymmetrical deposition is performed on a thick-walled microtube (tube-II). Distinct wavelength-dependent tuning was revealed in both kinds of tubes. Numerical calculations based on perturbation theory are carried out to explain and confirm the experimental results.

Localized Surface Plasmons Selectively Coupled to Resonant Light in Tubular Microcavities

“…3a and c. The calculated results agree well with the measured optical modes for both microcavities. The tuning of the optical modes in rolled-up microcavities by post-deposition of thin films has been discussed in previous works [32,33], and can be incorporated in the equations by modifying the quasi-potential k circ (z) employing perturbation theory [34,35]. The variation of k circ (z) (=ω/c) caused by the thin film deposition is determined by and E 5 exhibit a larger blueshift in comparison to the even order axial modes E 2 , E 4 and E 6 .…”

Dynamic Molecular Processes Detected by Microtubular Opto‐chemical Sensors Self‐Assembled from Prestrained Nanomembranes

“…The tube diameter measures around 5.8 μm, which is close to the minimum achievable size for low refractive index micro‐resonators working in the visible spectral range. After the roll‐up process, a 30 nm thick film of hafnium oxide (HfO 2 ) was grown on the microtube surface using atomic‐layer‐deposition (ALD) to increase the structural stability 31. Dynamic molecular processes of H 2 O and C 2 H 5 OH are detected on the thin nanomembrane surface.…”

“…Since the molecular layer thickness is much smaller than the tube diameter, perturbation theory is a suitable tool to calculate the mode shift induced by small structural changes on the cavity surface 31, 40. Based on this method, the thin molecule layer induced mode shift (Δ ω ) is calculated by: where $ \varepsilon \left({\overline r} \right) $ , ω and $ E\left({\overline r} \right) $ are the permittivity, resonance angular frequency, and the electric field distribution in the ring resonator model, respectively.…”

Optical microcavities with tubular geometry: properties and applications

“…All the methods mentioned above have their own characteristics and several methods can be used in conjunction to solve a problem. The perturbation theory is quite effective and suitable for the calculation of defects in microcavities or nanoparticles on the surface of tubular microcavities . Both the Mie scattering theory and adiabatic approximation have been employed to determine the optical axial confinement and more details concerning 3D optical confinement can be found later in Section .…”