Reconfigurable optical-force-drive chirp and delay line in micro- or nanofiber Bragg grating

Abstract

The emergence of optical micro/nano-fiber (MNF) with a subwavelength diameter, which has ultra-light mass and an intense light field, brings an opportunity for develop fiber based optomechanical systems. In this study, we theoretically show an optomechanical effect in silica MNF Bragg gratings (MNFBGs). The light-induced mechanical effect results in continuously distributed strain along the grating. It is shown that the power-related strain introduces an optically reconfigurable chirp in the grating period. We develop new optomechanical coupled-mode equations and theoretically analyze the influence of the optical-force-induced nonlinearity and chirp on the grating performance. Compared with weak Kerr effect, the optomechanics effect dominated in the properties evolution of MNFBGs and significant group velocity reduction and switching effect have been theoretically demonstrated at medium power level. This kind of optomechanical MNFBG with optically reconfigurable chirp may offer a path toward all-optical tunable bandwidth of Bragg resonance and may lead to useful applications such as all-optical switching and optically controlled dispersion and slow/fast light.

Optical microfiber or nanofiber: a miniature fiber-optic platform for nanophotonics

“…Based on this optomechanical effect, an MNF-based all-optical switch was demonstrated, possessing a turnoff time of ∼500 ms and recovery time of ∼760 ms [94] . In 2015, Luo et al presented a detailed theoretical model of the optomechanical effect in a silica MNF Bragg grating [528] . The light-induced strain along the grating introduced an optically reconfigurable chirp in the grating period and optical delay at a shorter wavelength, which is promising for all-optical switching and tunable optical delay lines.…”

[INVITED] Optical microfibre devices

“…As a large fraction of power propagates in the evanescent field, by positioning an OM in proximity of a periodical structure, it is possible to form external gratings [153] which can be used for sensing [154][155][156]. Bragg gratings and long period gratings have been inscribed in OMs also using ion-beam milling [157] fs and CO 2 lasers [158] and lead to numerous applications of OM gratings [159]. The OM large evanescent field has also been used in conjunction with graphene to modulate light and sensing applications [160][161][162].…”