Enhanced Nonlinear Optical Response of One-Dimensional Metal-Dielectric Photonic Crystals

We describe a new type of artificial nonlinear optical material composed of a one-dimensional metal-dielectric photonic crystal. Because of the resonant nature of multiple Bragg reflections, the transmission within the transmission band can be quite large, even though the transmission through the same total thickness of bulk metal would be very small. This procedure allows light to penetrate into the highly nonlinear metallic layers, leading to a large nonlinear optical response. We present experimental results for a $\mathrm{C}\mathrm{u}/{\mathrm{S}\mathrm{i}\mathrm{O}}_2$ crystal which displays a strongly enhanced nonlinear optical response (up to $12X$) in transmission.

Figure 1

Measured transmission spectra of the 40 and 80 nm thick bulk copper samples and the metal-dielectric photonic-crystal (MDPC) sample.

Figure 2

Numerically calculated $E$-field distribution within the bulk 40 nm sample at 650 nm (a) and the MDPC sample at a wavelength of 580 nm (out of resonance) and 650 nm (in resonance) (b). The field distribution is normalized to the incident field.

Figure 3

$Z$-scan traces showing the normalized transmission of the bulk (circles) and MDPC (diamonds) samples at $\lambda =650\mathrm{n}\mathrm{m}$ as a function of the distance from the focal point. The intensity at the focus was $500\mathrm{M}\mathrm{W}\mathrm{/}{\mathrm{c}\mathrm{m}}^{\mathrm{2}}$. The solid lines represent the fit obtained by numerical calculations.

Figure 4

Measured nonlinear fractional change in transmission (diamonds) and reflectivity (triangles) as functions of wavelength for the MDPC sample. The fractional change in transmission of the bulk Cu (circles) is shown for comparison. The intensity at the focus was $200\mathrm{M}\mathrm{W}\mathrm{/}{\mathrm{c}\mathrm{m}}^{\mathrm{2}}$. The solid lines represent the phenomenological model described in the text. Note the minus sign on the vertical axis; the transmission decreases with intensity.