Analysis of radiation pressure induced nonlinear optofluidics

Abstract

We analyze two nonlinear optofluidic processes where nonlinearity is induced by the interplay between optical field and liquid interface. Specifically, guided optical waves generate radiation pressure on the liquid interface, which can in turn distort the liquid interface and modify the properties of the optical field. In the first example, we discuss the feasibility of nonlinear optofluidic solitons, where optical field is governed by the nonlinear Schrödinger equation and nonlinearity is effectively determined by liquid properties. Then, we analyze a nonlinear optofluidic process associated with a high quality (Q) factor whispering gallery mode (WGM) in a liquid droplet. Similar to Kerr effects, the WGM can produce a frequency shift proportional to the WGM power. Using liquid properties that are experimentally attainable, we find that it may only take a few photons to generate measurable WGM resonance shift. Such a possibility may eventually lead to nonlinear optics at single photon energy level.

Comparative analysis of nonlinear optofluidic processes in microdroplets

“…As discussed in Ref. [17,18], the droplet interface deformation may induce a WGM resonance frequency shift, which is similar Due to the normalization, each curve shown here is in fact a collection of twelve curves (see Table I) collapsed together. The inset shows the magnitude of the droplet interface deformation at the equator (|∆R(π/2)/a|).…”

“…1. By assuming a transverse electric (TE) mode, the optical field in the resonator has been calculated analytically in [17,24], the derivations of which will not be repeated here. In this paper, we denote variables associated with the core phase with subscript "co" and the cladding phase with subscript "cl".…”

“…[18], the fluid motion induced by the optical radiation pressure, [9,17], is also governed by Eqs. (5a) and (7a) with the total stress on the interface f = (2σκ m − p opt )n.…”

“…[17,18], we analyzed a highly nonlinear optofluidic system that is comprised of light circulating in a liquid droplet in the form of a high quality (Q) factor whispering gallery mode (WGM). In such a system, the radiation pressure of the high-Q WGM can push the droplet surface outwards and form the bulge depicted in Fig.…”

Radiation-pressure-induced nonlinearity in microdroplets

“…The impact of the deformed liquid systems on the optical fields, however, was not considered. In a recent work [29], we first considered optical fields and liquids as a single system coupled together through optical radiation pressure. Under such a framework, we predict many interesting phenomena such as optofluidic solitons and single-photon-level nonlinearity.…”