Toggling between active and passive imaging with an omni-resonant micro-cavity

While passive illumination schemes often utilize a broadband spectral acceptance, the performance of active illumination with a laser is improved by narrowband spectral filtering at the sensor. We present an experimental demonstration of an optical cavity structure that is capable of toggling between two performance limits: narrowband resonant and broadband omni-resonant transmission. To achieve omni-resonance without modifying the cavity, the incident optical field is pre-conditioned by associating each wavelength with a particular incidence angle that enables a broad continuous spectrum to resonate with the cavity. This strategy can help seamlessly combine passive and active illumination in the same system.