Laser diffraction microscopy

Abstract

Final peer-reviewed manuscript of Rep. Prog. Phys. 72 (2009) AbstractCrystals composed of micrometer size colloidal particles diffract light and are both of fundamental interest as well as have important applications as filters, sensors and photonic devices. Laser light is used to diffract from these crystals in close analogy to x-ray or electron diffraction used for atomic crystals. Laser diffraction microscopy explores optical diffraction contrast to image crystals and crystal defects in analogy to the transmission electron microscopy technique used to image their atomic counterparts. This review discusses the application of optical diffraction contrast imaging to elucidate colloidal crystal nucleation and growth, and defect propagation. Diffraction contrast is described in terms of optical scattering theory and kinematical diffraction contrast theory developed for electron microscopy. Complementary information at the particle scale is obtained with high-resolution confocal microscopy. Confocal image stacks provide insight into the three-dimensional topology of defects and the interplay between applied strain and thermal fluctuations that governs defect nucleation.

Double Hexagonal Close Packed Structure Revealed in a Single Colloidal Crystal Grain by Bragg Rod Analysis

“…The intensity fluctuations are described by a model that takes into account the stacking sequence of a finite number of close-packed hexagonal layers. Using the model, two stacking sequences of research papers The normalized experimental Bragg peak profile along the 11l direction fitted with a peak model for 12 layers [equation (3) Although we have taken a relatively simple approach for the analysis of the stacking sequence, our conclusions are consistent with the preliminary results of our independent analysis of three-dimensional electron-density distribution in real space, obtained using a phase retrieval algorithm (Shabalin et al, 2014). With this method, the positions of the individual colloidal particles are determined and, by analysing the projection on one of the crystallographic directions, the stacking sequence can be determined.…”

Revealing Three-Dimensional Structure of an Individual Colloidal Crystal Grain by Coherent X-Ray Diffractive Imaging

“…On the other hand, controlled incorporation of certain defects can be desirable to enhance the functionality such as creating wave guides [21,22], trapping photons [12,23], and developing optical chips [24]. In these studies, monitoring an internal 3D structure of colloidal crystals including defects in real time remains a challenge [25].Among widely used techniques of the colloidal crystal structure investigation are optical microscopy [26,27] and confocal laser scanning microscopy [28]. However, the range of applications of these methods is strongly reduced by the limited resolution (at best about 250 nm) and the need of a careful refractive index matching, which is not always possible.…”

Colloidal Crystallization in 2D for Short-Ranged Attractions: A Descriptive Overview

“…Perhaps, the introduction of a balanced dynamics, considering not only the T2 processes but also coalescence with vanishing GBs would be beneficial to those models. Experimentally, colloidal particles have shown to be a useful model system where to probe atomistic phenomena [3][4][5][6][7]. Their large size (∼µm) and slow motion (∼s) allow us to use simple optical techniques, like video microscopy, to study the crystallization phenomena.…”

“…One of the reasons for this is the possibility to adjust the interaction potential between the particles by chemically modifying their surfaces, which would allow us to study the many different structures obtained by self-assembly. Another important reason is the capability of researchers to study the crystallization process by direct observation with simple laser diffraction and optical video microscopy, given that their size and interparticle distance is usually comparable to the wavelength of visible light and that their dynamics is slow enough to follow the trajectories of the individual particles [3][4][5][6][7]. Last but not least in importance is the possibility of applying some of the colloidal crystalization results to the self-assembly of proteins in their native globular state, a topic with the utmost attention paid in recent years; although in this case, by their very nature, the interaction between the proteins is not isotropic as with spherical colloidal particles, which enriches but complicates the problem [8].…”