Electron-beam fabricated high-efficiency convex gratings enable compact Offner and Dyson imaging spectrometers.

Gray-scale occulting masks enable coronographs to perform very high contrast imaging for detecting earth-like planets orbiting nearby stars.

Nano-patterned wires directly fabricated on image sensors work as broadbank optical polarizers.

The MDL's primary tool for nanoscale patterning, the electron-beam lithography system, has proven to be very flexible and allowed MDL to develop unique diffractive optical elements that enable a variety of instruments, including a number of airborne and spaceborne imaging spectrometers.

MDL developed electron-beam techniques for fabricating analog surface-relief diffractive optics. Our precise analog surfaces exhibit very high wavefront accuracy and efficiency. Using this technique, MDL fabricated a variety of diffractive optics, including microlenses for focal-plane arrays, gratings, and computer-generated holograms for optical interconnects and computed-tomography imaging spectrometers. By taking advantage of the electron-beam's significant depth-of-focus and precise calibration facilities, we developed schemes for fabricating analog surface profiles on substrates having several millimeters of center-to-edge height variation. This ability allowed MDL to fabricate high efficiency (>90%) convex gratings for so-called 'Offner' imaging spectrometers that are compact and can be designed to exhibit near-perfect spectral imaging.

The recent advent of extremely broadband focal-plane arrays drove the desire to design and fabricate gratings that had usable efficiency over multiple octaves. To accomplish this, we fabricated dual-blaze gratings composed of areas that are blazed at different wavelengths. This approach was used to fabricate gratings for CRISM (Compact Reconnaissance Imaging Spectrometer for Mars) that is flying aboard Mars Reconnaissance Orbiter. In an effort to improve on the multi-blaze scheme, MDL developed shaped-groove gratings (SGGs). Through the use of computer optimization techniques, we can design the shape of the grating groove to achieve a desired efficiency vs. wavelength function. This is useful to the spectrometer designer as it allows flattening of the overall signal-to-noise response of the instrument, taking into account the source spectrum and the detector responsivity.