Athermal silica-based interferometer-type planar light-wave circuits were realized by a newly developed multicore fabrication method. In this method, inductively coupled chemical-vapor deposition and polishing technologies are adopted on a silica substrate with a trench-type waveguide pattern prepared by reactive ion etching. Two kinds of deposited core material, 10GeO2-90SiO2 (mol. %) and 8GeO2-5B2O3-87SiO2 (mol. %), which show wavelength temperature dependence of 9.7 and 8.1 pm/degree C, respectively, were used to prepare the waveguide sections in a device. By adjustment of the lengths of waveguide sections with these two different core materials, athermal characteristics of less than 0.5 pm/degree C were achieved for Mach-Zehnder interferometer filter devices at the 1.55-microm wavelength range while the temperature varied from -20 to 80 degrees C. The new method is also applicable for the preparation of many other kinds of functional devices.
An infrared (IR) dual band multi-element detector with the abilities of dual band IR counter-countermeasure (IRCCM) and spatial filtering is presented for effective target detection in a complex tactical environment. The detection elements of the detector are specially arranged like a conventional reticle pattern. With special design, the ratio of radiation intensity from two IR bands can be calculated to distinguish the target from the IR target-flare mixed signal and the two detection bands use a common aperture in the seeker. Without a reticle in the optical system of the IR seeker, the dual band detector can still perform spatial filtering to eliminate background noise effectively. The design details of the detector are presented. The performance of the detector's dual band IRCCM and spatial filtering are analyzed. Simulation results are presented verifying validity of the presented method.
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