GAUSSIAN OPTICS COMPONENTS FOR USE AT MILLIMETER AND SUBMIL-LIMETER WAVELENGTHS

THE SCOPE OF THIS PROJECT IS TWOFOLD. ONE PART COMPRISES A STUDY OF A FOCAL PLANE IMAGING SYSTEM TO BE USED FOR PLASMA DIAGNOSTICS. PLASMA IS MEASURED AT SUBMILLIMETER WAVELENGTHS (FREQUENCIES ABOVE 300 GHZ) BY INTERFEROMETRY AND AT MILLIMETER WAVELENGTHS (30-300 GHZ) BY REFLECTOMETRY AND SPECTROMETRY. ONE DRAWBACK WITH THESE TECHNIQUES IS THAT ONLY A SINGLE DATA POINT CAN BE MEASURED IN A GIVEN TIME FRAME. FOCAL PLANE IMAGING IS A TECHNIQUE ENABLING THEUSER TO FORM A TWO-DIMENSIONAL MAP OF THE PLASMA, ALLOWING OBSERVATIONS OF SHORT DEVIATION PHENOMENA OVER A LARGE FIELDOF VIEW. ALTHOUGH THERE ARE OTHER TECHNIQUES, FOCAL PLANE IMAGING IS THE OPTIMUM METHOD BECAUSE THE USE OF QUASIOPTICAL COMPONENTS WOULD REDUCE LOSSES AND CAUSE NO PHASING PROBLEMS. THE REALIZATION OF THIS TECHNIQUE REQUIRES A NEW GENRE OF COMPONENTS THAT WILL BE DEVELOPED IN THE SECOND PART OF THIS PROJECT. MICROWAVE TEST COMPONENTS ARE ABUNDANT IN WAVEGUIDE BANDS THROUGH WR-6. ABOVE THESE FREQUENCIES, WHERE MANY PLASMA EXPERIMENTS ARE CONDUCTED, DEVICES SUCH AS ISOLATORS AND CIRCULATORS TEND TO BE LOSSY AND NARROW BAND BECAUSE OF SMALL SIZE, TOLERANCES, AND MATERIALS LIMITATIONS. GAUSSIAN OPTICS COMPONENTS ARE A PROMISING ALTERNATIVE TO THEIR WAVEGUIDE COUNTERPARTS. THESE DEVICES UTILIZE THE PROPAGATION OF A GAUSSIAN BEAM THROUGH FREE SPACE WITHOUT THE PROPAGATING ENERGY BEING CONFINED BY METALLIC OR DIELECTRIC BOUNDARIES. THE DEVICES MAY BE COUPLED TO A WAVEGUIDE SYSTEM BY A SCALAR FEEDHORN OR THEY MAY BE PART OF A SYSTEM CONSISTING ENTIRELY OF BEAM WAVEGUIDE. THE ADVANTAGES OF BEAM WAVEGUIDE OVER NORMAL WAVEGUIDE ARE LOW LOSS AND HIGH POWER HANDLING CAPABILITIES. FARADAY ROTATION ISOLATORS ANDCIRCULATORS WITH GAUSSIAN OPTICS WILL BE DEVELOPED FOR LOW POWER USE IN THE NEAR MILLIMETER AND SUBMILLIMETER WAVELENGTH REGIONS. HEXAFERRITE ISOLATORS AND AN OPTICAL PRECISION ATTENUATOR WILL BE DEVELOPED FOR USE BELOW 100 GHZ. THE SPECIFICATIONS AND PERFORMANCE OF THE IMAGING SYSTEM WILL THEN BE DETERMINED.