Optomechanical Wavelength and Energy Conversion in High-$Q$ Double-Layer Cavities of Photonic Crystal Slabs

We demonstrate that ultrasmall double-layer photonic-crystal-slab cavities exhibit a very high-$Q$ value for a wide range of the layer spacing, which enables us to realize unique optomechanical coupling. By mechanically varying the separation, we can achieve extraordinarily large wavelength conversion. In addition, the light stored in the cavity can generate a large radiation force. We show that this system exhibits extremely high energy conversion efficiency between optical and mechanical energy, leading to a novel approach for the optomechanical control of light and matter.

Figure 1

(a) Schematic of a DL-PCS cavity. (b) Schematics of cavity $A$ and $B$. The lattice constant $a=420\mathrm{nm}$, and the hole radius $r=0.275a$. For cavity $A$, the C-hole ($r=0.175a$) is shifted in the $y$ direction by $0.2a$. For cavity $B$, the C1, C2, and C3 holes are shifted in the $x$ direction by 9, 6, and 3 nm. (c),(d),(e) Field ($|H_z{|}^2$) distribution of the fundamental even mode with $d=210\mathrm{nm}$ (c),(d) and with $d=540\mathrm{nm}$ (e).

Figure 2

Resonant wavelength (${\lambda }_r$) and quality factor ($Q$) as a function of $d$ for cavity $A$ and cavity $B$.

Figure 3

Adiabatic wavelength conversion. (a) The temporal variation of $d$. (b) Wavelength spectra with and without dynamic tuning, which are obtained by Fourier conversion of data after the tuning.

Figure 4

(a) The radiation force and impulse per unit (pJ) energy versus $d$. (b) The slab shift induced by $F$ in (a) as a function of time for different $U$. (c) The energy conversion efficiency as a function of the initial $U$ for different cavities.