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

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

Figure 1

(a) Schematic of the MNFBG structure. The notation used is also illustrated. (b) Values for nonlinear and optomechanical parameters of silica MNFBGs at different radii. Black squares represent the nonlinear parameter and red circles represent the optomechanical parameter. The black solid line and the red solid line represent the fitted curves.

Figure 2

Transmission spectra of the 300-nm-radius MNFBG with normalized output power of $5\times {10}^{-5},5\times {10}^{-3},4.5\times {10}^{-2}$, and 0.125.

Figure 3

Time-averaged strain distribution in the MNFBG with a 300-nm radius at incident wavelengths of (a) 1550.00 nm and (b) 1549.90 nm.

Figure 4

(a) Reflection delay of the 300-nm-radius MNFBG at a normalized output power of $4.5\times {10}^{-2}$. (b) Transmission delay of the 300-nm-radius MNFBG at a normalized output power of $4.5\times {10}^{-2}$.

Figure 5

Relation between normalized incident power and transmittance of the 300-nm-radius MNFBG at wavelengths of 1549.84, 1549.87, 1549.90, and 1550.00 nm.