A numerically stable and systematic implementation of the rigorous coupled-wave analysis (RCWA) for the general multilayered grating structures is presented for both TE and TM modes. Numerical results of the approach are shown for the diffraction-based optical device as an example and are compared with the scalar diffraction method to illustrate the limited applicability of the scalar analysis.
A diffraction-based interferometric optical detection method for micromachined acoustic sensors can provide better sensitivity as compared to conventional capacitance detection schemes especially at low frequency range. The optical detection method, complete with optoelectronics readout, can be integrated with a capacitive micromachined acoustic transducer. The method is utilized on a 19×19 capacitive micromachined ultrasonic transducer (cMUT) array to demonstrate ultrasonic imaging of wire targets at 750kHz in air. A silicon photodiode (PD) array is also designed and fabricated in a standard 1.3μm CMOS technology, and through-wafer etching of holes for optical interconnect is performed on the same silicon platform. Further improvement of displacement sensitivity in a resonant-cavity-enhanced (RCE) acoustic sensor is theoretically analyzed including the loss effect in the mirror, and the theoretical results are experimentally verified by measurements on devices with a thin metallic bottom mirror made of silver.
Irradiating a microwave of several tens GHz on Bi2Sr2CaCu2O8+(delta ) (Bi-2212) single crystals, we observed genuine zero-crossing current steps from intrinsic Josephson junctions forming on the surface of the crystals in contact with normal- metallic (AU) electrodes. The critical current of the surface intrinsic Josephson junction was significantly suppressed due to the proximity contact to the normal-metal electrode, which allowed us to isolate the microwave response of the 'surface junction' from that of rest of the 'inner junctions' in a stack. This indicates that sufficiently small tunneling critical current density is essential to observing the zero-crossing current steps. An attempt to reduce the interlayer coupling using HgI2-intercalated Bi2Sr2CaCu2O8+(delta ) single crystals, however, gave rise to coherent fluxon motions.