Characterization of an imaging multimode optical fiber using digital micro-mirror device based single-beam system

This work demonstrates experimental approaches to characterize a single multimode fiber imaging system without a reference beam. Spatial light modulation is performed with a digital micro-mirror device that enables high-speed binary amplitude modulation. Intensity-only images are recorded by the camera and processed by a Bayesian inference based algorithm to retrieve the phase of the output optical field as well as the transmission matrix of the fiber. The calculated transmission matrix is validated by three standards: prediction accuracy, transmission imaging, and focus generation. Also, it is found that information on mode count and eigenchannels can be extracted from the transmission matrix by singular value decomposition. This paves the way for a more compact and cheaper single multimode fiber imaging system for many demanding imaging tasks

Filamented Light (FLight) Biofabrication of Highly Aligned Tissue-Engineered Constructs.

Cell-laden hydrogels used in tissue engineering generally lack sufficient 3D topographical guidance for cells to mature into aligned tissues. A new strategy called filamented light (FLight) biofabrication rapidly creates hydrogels composed of unidirectional microfilament networks, with diameters on the length scale of single cells. Due to optical modulation instability, a light beam is divided optically into FLight beams. Local polymerization of a photoactive resin is triggered, leading to local increase in refractive index, which itself creates self-focusing waveguides and further polymerization of photoresin into long hydrogel microfilaments. Diameter and spacing of the microfilaments can be tuned from 2 to 30 µm by changing the coherence length of the light beam. Microfilaments show outstanding cell instructive properties with fibroblasts, tenocytes, endothelial cells, and myoblasts, influencing cell alignment, nuclear deformation, and extracellular matrix deposition. FLight is compatible with multiple types of photoresins and allows for biofabrication of centimeter-scale hydrogel constructs with excellent cell viability within seconds (<10 s per construct). Multidirectional microfilaments are achievable within a single hydrogel construct by changing the direction of FLight projection, and complex multimaterial/multicellular tissue-engineered constructs are possible by sequentially exchanging the cell-laden photoresin. FLight offers a transformational approach to developing anisotropic tissues using photo-crosslinkable biomaterials

Thermal phase change actuator for self-tracking solar concentration

We present a proof of principle demonstration of a reversible in-plane actuator activated by focused sunlight, and describe a concept for its use as a self-tracking mechanism in a planar solar concentrator. By actuating at the location of focused sunlight and splitting the solar spectrum for actuation energy, this phase change device aims to provide the adaptive mechanism necessary to efficiently couple concentrated solar light from a lens into a planar lightguide in a manner that is insensitive to incidence angle. As a preliminary demonstration we present a planar actuator array capable of in-plane deflections of > 50 mu m when illuminated with focused light from a solar simulator and demonstrate solar light activated frustrated total internal reflection (FTIR) with the actuator array. We further propose how this solar induced FTIR effect can be modified using a dichroic facet array to self-adaptively couple and concentrate solar light into a planar lightguide. (C) 2012 Optical Society of Americ

Media 2: Thermal phase change actuator for self-tracking solar concentration

Originally published in Optics Express on 05 November 2012 (oe-20-S6-A964

Media 1: Thermal phase change actuator for self-tracking solar concentration

Originally published in Optics Express on 05 November 2012 (oe-20-S6-A964