Abstract: One aspect of the invention relates to a PLC containing at least one waveguide on a bottom clad layer, each waveguide having a top cap layer on an upper surface thereof, and a top clad layer over the waveguides having the top cap on the upper portion thereof. The presence of the top cap reduces waveguide birefringence and resultant polarization dependence in PLCs, particularly for reducing polarization dependent wavelength shift in AWGs. Another aspect of the invention relates to methods of making PLCs involving forming a waveguide layer on a bottom clad layer, forming a top cap layer on the waveguide layer, patterning the waveguide layer and the top cap layer using a mask to form waveguides having a top cap on an upper portion thereof, and forming a top clad layer over the waveguides having the top cap on the upper portion thereof.

Abstract: A sensor for measuring the non-methane HC concentration of gas sample, e.g., automotive exhaust gas, the sensor comprises a sensor base, capable of producing a output signal representative of the exothermic effect of the hydrocarbon species in the gas sample. The sensor base has disposed on, and integral with, its surface, a porous selective oxidation catalyst layer comprising capable of selectively oxidizing a combination of CO+H2+alkene species in the gas sample and leaving unoxidized the alkane and aromatic hydrocarbons. The sensor base further includes a first supported resistance temperature device which has disposed thereon a total oxidation catalyst layer capable of oxidizing the remaining alkane and aromatic hydrocarbon species in the gas sample, and a non-catalyzed second resistance temperature device.

Abstract: A system for measuring the non-methane HC concentration of gas sample, e.g., automotive exhaust gas, comprises a sensor catalyst capable of selectively oxidizing the combination of CO+H2+alkene hydrocarbons in a gas sample and a catalytic differential calorimetric sensor downstream of the sensor catalyst, capable of producing an output signal representative of the exothermic effect of oxidation of the remaining aromatic and alkane hydrocarbons in the gas sample. The system also includes a heater for maintaining both the sensor catalyst and the catalytic calorimetric sensor at a temperature sufficient to achieve substantially complete oxidation of the CO+H2+alkene hydrocarbon combination and the aromatic and alkane hydrocarbons, respectively. Lastly, the system includes a means for analyzing the output signal representative of the concentration of unburned aromatic and alkane hydrocarbons in the exhaust gas to determine concentration of the total non-methane hydrocarbon species.