Spectral and imaging characteristics of a tunable ultra-narrow photonic-crystal interferometer for space-based applications

High-finesse Fabry-Perot interferometers are useful tools when it comes to high-resolution spectroscopy and narrow-band filtering. Rugged, reliable, narrow-band tunable filters are of special interest for remote sensing from ground, airborne and space-based platforms. This report discusses the results of a numerical analysis and experimental study of such a filter with its design based on the unique features of the photonic crystal interferometer (PCI). An optimal choice of the PCI components and their parameters allows achieving a sub-angstrom bandpass combined with a broad tunability range (< 10 nm) in the visible spectral regions. The prototype PCI system has the tunability over a 1 nm with a bandpass near 0.02 nm and an acceptance angle about 1 angular degree. Detailed consideration is given to the imaging characteristics of such an interferometer, and their dependence upon the quality of the individual components (i.e. the mirror substrates, dielectric layers, etc.). In summary, we present the results of the theoretical analysis and experimental study of the spectral and imaging characteristics of a high-finesse PCI, and their impairments due to deviations from the required parameters of the optical elements.