Abstract

Photonic crystals are materials with a dielectric property periodicity, which results in linear or nonlinear light property modulation.¹ Recent studies on man-made nano-periodic structures indicate strong enhancement in second-harmonic-generation (SHG)² due to the break down of optical centro-symmetry within the materials. Such SHG enhancement by the existence of photonic crystal effect has also been demonstrated using Hyper-Rayleigh scattering recently.³ Therefore, it is reasonable to speculate that the highly organized biological nano-structures may all behave as nonlinear photonic crystals. Examples of highly organized biological nano-structures include stacked membranes, such as myelin sheath, endoplastic reticulum, grana in the chloroplast, Golgi apparatus, microhbrils and collagen bundles. Here we present a study using a multi-modal nonlinear microscopy,⁴ which reveals nonlinear optical activities in those naturally occurring biophotonic crystalline structures. This technique, based on a femtosecond Cnforsterite laser at 1230 nm, combines different imaging modalities including second-, third-harmonic generations, and multi-photon fluorescence.

© 2002 Optical Society of America