Near-field second-harmonic generation

Abstract

Near-field microscopy of second-harmonic generation combines high surface sensitivity of the nonlinear optical process and high spatial resolution of the near-field optics. It enables investigation of nonlinear optical phenomena at the nanoscale and provides an opportunity to develop a highly sensitive optical technique for materials characterization. In this paper we overview apertured and apertureless near-field approaches for local studies of second-harmonic generation. Near-field second-harmonic generation at metal surfaces and nanostructures and related electromagnetic field enhancement and confinement effects are considered. The latter demonstrates the feasibility of achieving nanoscale light sources using second-harmonic generation. Applications of second-harmonic near-field microscopy for characterization of magnetic and ferroelectric materials are also discussed. Nonlinear nano-optics can lead to the development of novel photonic devices on the sub-wavelength-scale as well as new tools for imaging and local optical studies of materials, chemical and biological species.

Second‐harmonic microscopy of ex vivo porcine corneas

“…For biological samples, two‐photon fluorescence microscopy has become a well‐established technique that allows for large penetration depths (∼mm) and a minimum of light‐induced damage as the interaction is essentially confined by the focal volume. Likewise, second‐harmonic (SH) generation microscopy has shown great potential in the imaging of photonic materials down to a nanoscale (Vohnsen & Bozhevolnyi, 2001; Vohnsen et al ., 2001; Labarthet & Shen, 2003; Zayats & Smolyaninov, 2004), to reveal local symmetries in biological samples (Moreaux et al , 2000), visualization of muscle tissues (Freund & Deutsch, 1986; Chu et al ., 2003) and the fibril organization in collagen‐rich tissues such as skin (Palero et al ., 2006), the cornea and the sclera of the eye (Hochheimer, 1982; Yeh et al ., 2002; Han et al ., 2004; Han et al ., 2005; Tan et al ., 2005; Teng et al ., 2006; Morishige et al ., 2007; Svoboda et al ., 2007; Vohnsen & Artal, 2007). Likewise, SH imaging has been successfully used to image the ex vivo optic nerve head (Brown et al ., 2007) with important implications for glaucoma analysis.…”