Second‐harmonic microscopy — a quantitative probe for molecular surface order

Abstract

Second‐harmonic microscopy—an application of which is presented in the previous article—is a fast quantitative technique for the imaging of interfaces such as that in the Figure. The theory of the technique, which is based on the generation of second‐harmonic light specifically at surfaces or interfaces due to their lack of centrosymmetry, is outlined and the interpretation of the results discussed.

POLAR MICRO STRUCTURES OF THE B2- AND B4-PHASES OF BENT-SHAPED LC-MOLECULES RESOLVED BY NONLINEAR OPTICAL MICROSCOPY

“…29 Besides, the scanning time required to acquire SHG imaging is also similar to that needed by other SHG imaging techniques, where for example, the entire sample surface should be illuminated by an extended fundamental beam and the SHG signal is collected by a CCD-array. 21,22 In the latter case however, the low SHG conversion produced by a weak unfocused beam, force integration times of the same order of magnitude, in order to reproduce sharp images of SHG active mono-domain structures. One advantage of the SHG-scanning microscope is the possibility of resolving spatially small features and details, with the possibility to select the desired spatial resolution, 9 where interesting NLO properties are detected.…”

Polarity of Organic Supramolecular Materials: A Tunable Crystal Property

“…Up to now, scanning pyroelectric microscopy (SPEM) was the only technique which was able to image the double-cone structure in real crystals (34,35). New experiments attempt to reveal cones by scanning SHG microscopy (36). However, just recently we succeeded in demonstrating polarization reversal in as-grown thin crystals by phase-sensitive SHG microscopy (37).…”

Domain Structure Studies in Phases of Bent-Shaped Molecules by Spatially Resolved Second Harmonic Microscopy

“…A stepping motor system holding the sample mount allows the scanning process in the x-y-plane with maximal spatial resolution of Dx ¼ Dy ¼ 1.25 mm and Dz ¼ 5 mm. The resolution is rather given by the spot-size of the laser beam, which was about 5 mm, and the scanning time was limited by the speed of the steeping motors system and DAQ-PC-board; in contrast to others SHG-Microscope systems where the resolution and speed are given by the integration time and the size of the pixel matrix of a CCD-array [19][20]. The second harmonic wave (k 2x ¼ 532 nm) is detected by an optical photomultiplier behind optical filters to cancel the fundamental wave.…”