Fast, frequency-agile, stimuli-responsive, and tunable (FAST) optical filters

In this STTR Phase I proposal, Kent Optronics and its partner Vanderbilt University propose to develop a monolithic fast speed self-responsive (passive) optical limiter comprising an array of Vanadium dioxide (VO2) thin film coated elements. It locally blocks dangerous laser via redirecting the laser beam mechanism, leading to an optical density (OD) > 6. The limiter has femtosecond (fs) response time due to the ultrafast VO2 phase transition.  When no laser, its 70% linear transmission enables high throughput for normal sensor operation.  The on-set laser blocking fluence threshold is 400X lower than most EO-IR sensors in the field. The limiter is reversible meaning its transmission returns to 70% once the laser disappears. The limiter is spectrally agile to block arbitrary single and multiple laser wavelengths simultaneously in the visible to short wave infrared.  Phase I efforts are to design and evaluate the technology via a feasibility study to finalize the limiter design against the design goals. In Phase II, a formal optical limiter prototype will be developed, qualified and delivered, reach TRL>6.