The ability of optical coherence tomography (OCT) to perform high-speed, micron-scale, cross-sectional imaging has transformed ophthalmic medicine and has the potential to transform cardiovascular, gastrointestinal, pulmonary, and dermatological medicine. Current OCT systems use raster scanning, a serial method for acquiring depth reflectivity profiles at different locations on a sample. Shifting the paradigm fro serial to parallel OCT will enable dramatically higher imaging rates. Higher imaging rates will enable the comprehensive quantification of previously inaccessible disease states including (a) mucus flow rates and ciliary motion dynamics in cystic fibrosis and (b) response to new drug treatments in disorders of epidermal differentiation. The missing component to enable parallel OCT is a bright light source with low spatial coherence. Random lasers are shown by our latest work to be uniquely suited for parallel OCT and represent a new kind of light source for coherent optical imaging. Our research therefore has two main aims. First, we will develop a novel edge-emitting semiconductor random laser with low spatial coherence. We recently demonstrated that specifically designed random lasers are simultaneously bright, broadband, and exhibit low spatially coherence. These proof-of-concept demonstrations were performed using dye-based random lasers. However, dye-based lasers have well-known drawbacks that limit their widespread use in medicine. On the other hand, semiconductor light sources are compact, lightweight, and energy efficient, making them ubiquitous in clinical medicine. By applying the design principles we identified in our dye laser research, we will develop an electrically pumped, edge-emitting broadband semiconductor random laser operating at 800 nm, a major OCT wavelength. The laser emission from the edge of the membrane will form a thin illumination strip that can be incorporated into a parallel line-field OCT system for high-speed, crosstalk free imaging. In addition to being a paradigm-shifting advance for OCT, our work has broad impact in using low spatial coherence lasers in biomedical imaging. Second, we will demonstrate parallel spectral domain OCT using a random laser and validate crosstalk rejection. The edge-emitting random laser will enable line-field parallel imaging in which depth reflectivity profiles re recorded from an entire line on the sample in a single snapshot. The spectral domain OCT system will use a high-speed imaging spectrometer in its detector arm. The ability of the system to reject crosstalk will be validated in a series of phantom imaging experiments. The OCT system developed here will serve as a prototype upon which future translational research will be developed.
Our research will develop new lasers that will enable much faster imaging of certain organs including the eye, esophagus, airways, skin, and blood vessels. Our research will benefit public health by enabling the more precise understanding, diagnosis, and treatment of diseases that can be imaged using light.
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| Redding, Brandon; Cerjan, Alexander; Huang, Xue et al. (2015) Low spatial coherence electrically pumped semiconductor laser for speckle-free full-field imaging. Proc Natl Acad Sci U S A 112:1304-9 |
| Redding, Brandon; Ahmadi, Peyman; Mokan, Vadim et al. (2015) Low-spatial-coherence high-radiance broadband fiber source for speckle free imaging. Opt Lett 40:4607-10 |
| Redding, Brandon; Bromberg, Yaron; Choma, Michael A et al. (2014) Full-field interferometric confocal microscopy using a VCSEL array. Opt Lett 39:4446-9 |
