No abstract

No abstract

A technique is proposed for measuring the linear birefringence and linear diattenuation of an optical sample using a polarimeter. In the proposed approach, the principal axis angle (alpha), phase retardance (beta), diattenuation axis angle (thetad), and diattenuation (D) are derived using an analytical model based on the Mueller matrix formulation and the Stokes parameters. The dynamic measurement ranges of the four parameters are shown to be alpha = 0 approximately 180 degrees, beta = 0 approximately 180 degrees, theta(d) = 0 approximately 180 degrees, and D = 0 approximately 1, respectively. Thus, full-range measurements are possible for all parameters other than beta. In this study, the proposed methodology does not require the principal birefringence axes and diattenuation axes to be aligned. In addition, the linear birefringence and linear diattenuation properties are decoupled within the analytical model, and thus the birefringence properties of the sample can be solved directly without any prior knowledge of the diattenuation parameters. Also, the characteristic parameters in the baked polarizer with linear birefringence are successfully extracted from an optically equivalent model and proved by the respective simulation and experiment introduced in this study.

An intrachip wireless interconnect using integrated antennas is demonstrated in a flip-chip ball grid array package. The wireless interconnect consists of a transmitter-receiver pair, which is fabricated in a 0.18-m CMOS process. A 15-GHz signal is generated and broadcasted across the integrated circuit. The signal is picked up by a receiver 4 mm away on the same integrated circuit and frequency divided by eight to produce a 1.875-GHz local clock signal. The interconnection is also demonstrated between a transmitting antenna and a packaged receiver 40 cm away from the transmitting antenna. Demonstration of intrachip wireless interconnects in a package has been considered the ultimate test for this technology.Index Terms-Flip-chip package, integrated antennas, wireless interconnection.

Abstract:In this review we discuss the advances in use of GaN and ZnO-based solid-state sensors for gas sensing applications. AlGaN/GaN high electron mobility transistors (HEMTs) show a strong dependence of source/drain current on the piezoelectric polarization -induced two dimensional electron gas (2DEG). Furthermore, spontaneous and piezoelectric polarization induced surface and interface charges can be used to develop very sensitive but robust sensors for the detection of gases. Pt-gated GaN Schottky diodes and Sc 2 O 3 /AlGaN/GaN metal-oxide semiconductor diodes also show large change in forward currents upon exposure to H 2 containing ambients. Of particular interest are methods for detecting ethylene (C 2 H 4 ), which offers problems because of its strong double bonds and hence the difficulty in dissociating it at modest temperatures. ZnO nanorods offer large surface area, are bio-safe and offer excellent gas sensing characteristics.

We report on a comparison of different gate oxides for AlGaN/GaN highelectron-mobility transistor (HEMT) pH sensors. The HEMTs show a linear increase in drain-source current as the pH of the electrolyte solutions introduced to the gate region is decreased. Three different gate oxides were examined, namely the native oxide on the AlGaN surface, a UV-ozone-induced oxide and an Sc 2 O 3 gate deposited by molecular beam epitaxy. The Sc 2 O 3 produced superior results in terms of resolution in measuring small changes in pH. The devices with Sc 2 O 3 in the gate region exhibited a linear change in current between pH 3 and 10 of 37 lA/pH with a resolution of <0.1 pH over the entire pH range. In contrast, the native oxide devices showed a larger change in current, $70 lA/pH, but with a degraded resolution of $0.4 pH. Results for the UV-ozone oxide were intermediate in resolution, 0.2 pH. These HEMTs have promise for detecting pH changes in biological samples and can be readily integrated into a standard package for wireless data transmission.

Peltier element cooling of ungated AlGaN/GaN high electron mobility transistors (HEMTs) is shown to be an effective method for condensing exhaled breath, enabling the measurement of the pH and glucose of the exhaled breath condensate (EBC). By comparison with standard solutions, the current change measured in the HEMTs with EBC shows that the sensitivity of the glucose detection is lower than the glucose concentration in the EBC of healthy human subjects and the pH of the condensate from the exhaled breath is within the range of 7-8, typical of that for human blood. The HEMT sensors can be integrated into a wireless data transmission system that allows for remote monitoring. Details of the transmitter and receiver design for the transmission system are given. Our work demonstrates the possibility of using AlGaN/GaN HEMTs for extended investigations of airway pathology without the need for clinical visits.

No abstract