Mechanical and Electric Control of Photonic Modes in Random Dielectrics
Dario Balestri, Maurangelo Petruzzella, Simona Checcucci, Francesca Intonti Niccolò Caselli Fabrizio Sgrignuoli, Frank W. M. van Otten, Andrea Fiore, Massimo Gurioli
Random dielectrics defines a class of non-absorbing materials where the index of refraction is randomly arranged in space. Whenever the transport mean free path is sufficiently small, light can be confined in modes with very small volume. Random photonic modes have been investigated for their basic physical insights, such as Anderson localization, and recently several applications have been envisioned in the field of renewable energies, telecommunications, and quantum electrodynamics. An advantage for optoelectronics and quantum source integration offered by random systems is their high density of photonic modes, which span a large range of spectral resonances and spatial distributions, thus increasing the probability to match randomly distributed emitters. Conversely, the main disadvantage is the lack of deterministic engineering of one or more of the many random photonic modes achieved. This issue is solved by demonstrating the capability to electrically and mechanically control the random modes at telecom wavelengths in a 2D double membrane system. Very large and reversible mode tuning (up to 50 nm), both toward shorter or longer wavelength, is obtained for random modes with modal volumes of the order of few tens of (λ/n)3.
a) Scanning electron microscopy image showing the upper freestanding microbridge, in planar view. The bottom panel is a cross view sketch with the definition of the parameters hand d0. b) Typical PL enhancement spectrum at a given tip position. Inset: histogram of the number of modes for different spectral ranges. c) Spectral and spatial detail of a random mode. Inset: map of the random mode. d) Maps of the maximum PL enhancement in six spectral regions. All the white scale bars in the figures correspond to 1 µm.