Microscopic imaging of cellular motility has recently advanced from two dimensions to three dimensions for applications in drug development. However, significant degradation in resolution occurs with increasing imaging depth, limiting access to motility information from deep inside the sample. Here, digital holographic optical coherence imaging is adapted to allow visualization of motility in tissue at depths inaccessible to conventional motility assay approaches. This method tracks the effect of cytoskeletal anti-cancer drugs on tissue inside its natural three-dimensional environment using time-course measurement of motility within tumor tissue.

This review covers a spectrum of optoelectronic properties of and uses for semi-insulating semiconductor heterostructures and thin films, including epilayers and quantum wells. Compensation by doping, implantation, and nonstoichiometric growth are described in terms of the properties of point defects and Fermi level stabilization and pinning. The principal optical and optoelectronic properties of semi-insulating epilayers and heterostructures, such as excitonic electroabsorption of quantum-confined excitons, are described, in addition to optical absorption by metallic or semimetallic precipitates in these layers. Low-temperature grown quantum wells that have an arsenic-rich nonstoichiometry and a supersaturated concentration of grown-in vacancies are discussed. These heterostructures experience transient enhanced diffusion and superlattice disordering. The review discusses the performance of optoelectronic heterostructures and microcavities that contain semi-insulating layers, such as buried heterostructure stripe lasers, vertical cavity surface emitting lasers, and optical electroabsorption modulators. Short time-scale applications arise from the ultrashort carrier lifetimes in semi-insulating materials, such as in photoconductors for terahertz generation, and in saturable absorbers for mode-locking solid state lasers. This review also comprehensively describes the properties and applications of photorefractive heterostructures. The low dark-carrier concentrations of semi-insulating heterostructures make these materials highly sensitive as dynamic holographic thin films that are useful for adaptive optics applications. The high mobilities of free carriers in photorefractive heterostructures produce fast dielectric relaxation rates that allow light-induced space-charge gratings to adapt to rapidly varying optical fringe patterns, canceling out environmental noise during interferometric detection in laser-based ultrasound, and in optical coherence tomography. They are also the functional layers in high-sensitivity dynamic holographic materials that replace static holograms in Fourier imaging systems and in experimental Tbit/s optical systems. Semi-insulating heterostructures and their applications have attained a degree of maturity, but many critical materials science issues remain unexplored.

Spinning biodisks have advantages that make them attractive for specialized biochip applications. The two main classes of spinning biodisks are microfluidic disks and bio-optical compact disks ͑BioCD͒. Microfluidic biodisks take advantage of noninertial pumping for lab-on-a-chip devices using noninertial valves and switches under centrifugal and Coriolis forces to distribute fluids about the disks. BioCDs use spinning-disk interferometry, under the condition of common-path phase quadrature, to perform interferometric label-free detection of molecular recognition and binding. The optical detection of bound molecules on a disk is facilitated by rapid spinning that enables high-speed repetitive sampling to eliminate 1 / f noise through common-mode rejection of intensity fluctuations and extensive signal averaging. Multiple quadrature classes have been developed, such as microdiffraction, in-line, phase contrast, and holographic adaptive optics. Thin molecular films are detected through the surface dipole density with a surface height sensitivity for the detection of protein spots that is approximately 1 pm. This sensitivity easily resolves a submonolayer of solid-support immobilized antibodies and their antigen targets. Fluorescence and light scattering provide additional optical detection techniques on spinning disks. Immunoassays have been applied to haptoglobin using protein A/G immobilization of antibodies and to prostate specific antigen. Small protein spots enable scalability to many spots per disk for high-throughput and highly multiplexed immonoassays.

..