We report an approach to build a tunable spectral imaging system operating in the long-wave infrared (λ=8-12 μm). In addition to broadband images, the imaging systems allows for tunable selection of particular passbands. The tunable passband selection allows the imaging system to focus on the infrared signatures (including both thermal emission signature related to object’s temperature and characteristic absorption signature) of object of interest. This is achieved by incorporating a fast tunable spectral filter comprising dispersive magneto-optic (MO) materials in the imaging system. The MO materials in the spectral filter are sandwiched between polarizers, and dispersion in the Faraday Effect rotates the polarization of different wavelengths of light by different amounts, which results in a wavelength-dependent attenuation by the subsequent polarizer. Multiple stages with different thicknesses of the MO material can be stacked (Lyot configuration) to further narrow down the transmission peak. The central wavelength of the filter can be tuned either by tuning the magnetic field B along the direction of the optical axis, or by rotating the polarizers while applying a fixed magnetic field. In the long-wave infrared, n-doped InSb proves to be a prominent MO material. We present detailed measurements of Verdet constant, absorption coefficient and calculated figure of merit (FOM) for a range of carrier concentrations near 1017 cm-3 in the long-wave infrared. A prototype tunable bandpass filter is constructed and demonstrated.
Optogenetic manipulation is widely used to selectively excite and silence neurons in laboratory experiments. Recent efforts to miniaturize the components of optogenetic systems have enabled experiments on freely moving animals, but further miniaturization is required for freely flying insects. In particular, miniaturization of high channel-count optical waveguides are needed for high-resolution interfaces. Thin flexible waveguide arrays are needed to bend light around tight turns to access small anatomical targets. We present the design of lightweight miniaturized optogentic hardware and supporting electronics for the untethered steering of dragonfly flight. The system is designed to enable autonomous flight and includes processing, guidance sensors, solar power, and light stimulators. The system will weigh less than 200mg and be worn by the dragonfly as a backpack. The flexible implant has been designed to provide stimuli around nerves through micron scale apertures of adjacent neural tissue without the use of heavy hardware. We address the challenges of lightweight optogenetics and the development of high contrast polymer waveguides for this purpose.