Tunable Mode Conversion Using Acoustic Waves in Optical Microwires

Abstract

We propose a tunable inline mode converter based on the acousto-optic effect in optical microwires. A theoretical model is developed to analyze the interaction between the acoustic waves and the optical modal coupling in microwires. We show that adjusting the acoustic wave frequency we can switch between different optical modes. The conversion efficiency can be adjusted through the acoustic wave amplitude.Index Terms-Acousto-optic effect, modal coupling, mode division multiplexing (MDM), optical microwires.

On-chip optical mode conversion based on dynamic grating in photonic-phononic hybrid waveguide

“… is an envelope function, and denotes the polarization direction of electric field. In the mode conversion between different optical modes with same polarization, the longitudinal acoustic wave modulates the refractive index of waveguide for forming a dynamic grating 5 . The longitudinal displacement components induced by acoustic wave can written as 15 …”

“…The acousto-optic effect is a specific case of photoelasticity, which can promote the diffraction of light by sound through a sonic grating 1 , and it has been successfully used in modulators 2 , frequency shifters 3 and tunable filters 4 . Recently, tunable mode conversions are implemented by utilizing the acousto-optic effect in optical fibers 5 6 7 , which is useful in mode division multiplexing (MDM) over multi-mode fibers. Meanwhile, the on-chip mode converter, serving as an important device to add and drop optical signals, has also been proposed as an important component in the integrated MDM systems 8 9 10 .…”

“…While resonant mode converter can be made very short, the difficulty is to determine the precise beat length due to device parameter variations from fabrication. With the external injection of the acoustic wave, the optical mode converters based on acousto-optic effect can relax the fabrication tolerance 5 6 . During the acousto-optic interaction process, the launched acoustic waves cause the geometrical deformation and refractive index change, leading to the establishment of dynamic grating 14 15 16 .…”

Narrowband fast tunable acousto-optic filter based on dispersion-compensating fiber

“…All-fiber acousto-optic tunable filters (AOTFs) 1 have been widely used in many fields, such as tunable lasers [2][3][4] , wavelength division multiplexing (WDM) optical communication [5][6][7] , optical signal processing 8,9 and so on. The all-fiber AOTF is considered to be a good candidate for the tunable add-drop filter (ADF) due to its high tuning speed 10,11 , large wavelength tuning range 12,13 , tunable coupling efficiency 14 , and compatibility with optical fiber system.…”

Analysis of optical OAM mode conversion using elastic vortex wave in graded-index optical fiber

“…18) Optical mode conversion in optical fibers using the AO effect has been reported in Refs. 19,20, in which the longitudinal or flexural mode is used as the elastic wave. Regarding OAM mode conversion, it is necessary to consider the matching of OAM between the incident optical beam and the elastic wave in addition to the conventional mode conversion.…”