Label-Free Optical Biochemical Sensors via Liquid-Cladding-Induced Modulation of Waveguide Modes.

We demonstrated modulation of the waveguide mode mismatch via liquid cladding of the controllable refractive index for label-free quantitative detection of concentration of chemical or biological substances. A multimode optical fiber with its core exposed was used as the sensor head with the suitable chemical modification of its surface. Injected analyte liquid itself formed the liquid cladding for the waveguide.

Use of the asymmetric planar hall resistance of an Fe film for possible multi-value memory device applications.

Systematic planar Hall measurements have been performed on a ferromagnetic Fe film grown on a standard (001) GaAs substrate at room temperature. The angular dependence of the planar Hall effect revealed the presence of both four-fold (cubic) and two-fold (uniaxial) anisotropies in the 7 nm thick Fe film. The dominance of the four-fold symmetric anisotropy, however, provided four magnetic easy axes near the (100) direction, which results in a two step switching phenomenon in the magnetization reversal process.

Metal-insulator oscillations in a two-dimensional electron-hole system.

The electrical transport properties of a bipolar InAs/GaSb system have been studied in a magnetic field. The resistivity oscillates between insulating and metallic behavior while the quantum Hall effect shows a digital character oscillating from 0 to 1 conductance quantum e(2)/h. The insulating behavior is attributed to the formation of a total energy gap in the system.