HfO2/SiO2 multilayers were deposited on single point diamond turned aluminum substrates via
modified reactive plasma ion assisted deposition to form a laser durable and environmentally
stable dielectric enhanced IR mirror at a wavelength of 1064nm. The effect of the surface quality
of the diamond turned aluminum on the optical performance of the dielectric enhanced mirror was
assessed. A laser-induced damage threshold up to 11 J/cm2 was obtained from the enhanced
aluminum mirror tested in pulse mode at 1064nm with a pulse length of 20ns and a repetition rate
of 20Hz. Laser damage morphology was revealed by a scanning electron microscopy. The damage
mechanism was attributed to nodule defects generated by particle embedded on the aluminum
substrate surface.
Dual band infrared imagers require a similar set of filters as are needed by single band infrared imagers but with the
added requirement of high transmission in the mid and far infrared. The design of discrete layer filters with optimized
dual band transmission is investigated for three types of filters. These are a visible-infrared beamsplitter, a long
wavelength edge filter and a dual bandpass cold filter. These designs illustrate the role that harmonic reflection bands
can play in the design of dual band filters. The visible reflection beamsplitter design does not have harmonics in the
infrared but requires additional layers to reduce reflection at mid and long wavelengths. The long wavelength edge filter
requires suppression of the second and third harmonics while the sensor band pass cold filter can use harmonics to
advantage. Design techniques are discussed and the results of an initial set of fabrication runs are presented to assess the
sensitivity of example designs to manufacturing errors.
Sensor performance for dual band forward looking infrared (FLIR) imagers can be substantially improved by increased simultaneous throughput of both sensor bands in the optical systems. Currently available antireflection coatings (ARs) have optimized performance for either spectral band, but not both on the same optic. Where AR coatings cover the mid and long wave infrared (LWIR) bands, or the entire broad band spectrum from visible to LWIR, performance is not sufficient for future systems. A method of designing and fabricating high performance ARs has been developed. This paper presents a discussion of the trade-off of film thickness and complexity versus transmission performance. Fabrication results for high, medium and low index lens materials are also presented.
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