Thin LiNbO3 on insulator electro-optic modulator.

This Letter presents a method for the fabrication and integration of a thin LiNbO3 substrate with a Si handle wafer. An inverted ridge structure guides a single optical mode in an electro-optic modulator fabricated on a mechanically thinned substrate. To define an optical waveguide, a ridge structure is first patterned on a 500 µm thick X-cut LiNbO3 wafer; then a low dielectric constant adhesive layer is used to bond the etched LiNbO3 to Si. The LiNbO3 is mechanically thinned to 4 µm, and planar electrodes are patterned. Experimental results demonstrating modulation with a V(π)L of 7.1 V-cm were shown, optical loss was low enough, and film quality high enough, to enable an interaction length of 0.8 cm.

Measured comparison of contrast and crossover periods for passive millimeter-wave polarimetric imagery.

Several targets are set-up outside and imaged by a passive millimeter-wave sensor over a 24 hour period. The sensor is capable of measuring two linear polarization states simultaneously and the contrasts of the targets are compared for the different polarizations. The choice of polarization is shown to have an impact on the contrast of different targets throughout the day. In an extreme case the contrast of a target experiences a crossover event and disappears for one polarization while it presents a strong contrast (9 K) with the other polarization. Experimental results are shown along with a simulation of the scene using a ray tracing program.