With a tunable refractive index, magnetic fluid can be applied to the development of adjustable optical devices. In this work, a magnetic-fluid-based optical switch is designed and characterized. The optical switch is formed by sealing magnetic fluid between two glass prisms. When a light is incident to one side of one of the prisms, a reflected light from the magnetic fluid film comes out from the same prism, whereas a transmitted light through the film emits from the other prism. It was found that the intensity ratio of the reflected light to the transmitted light can be manipulated by varying the external magnetic field strength. This implies that the light intensity can be switched between two paths. The switching efficiency also depends on the incident angle of a light into the prism. We then theoretically derive the incident-angle dependent switching efficiency to clarify relevant physical mechanisms.

Abstract.A nonlinear, adaptive method to remove the harmonic noise that commonly resides in geophysical data is proposed in this study. This filtering method is based on the ensemble empirical mode decomposition algorithm in conjunction with the logarithmic transform. We present a synthetic model study to investigate the capability of signal reconstruction from the decomposed data, and compare the results with those derived from other 2-D adaptive filters. Applications to the real seismic data acquired by using an ocean bottom seismograph and to a shot gather of the ground penetrating radar demonstrate the robustness of this method. Our work proposes a concept that instead of Fourier-based approaches, the harmonic noise removal in geophysical data can be achieved effectively by using an alternative nonlinear adaptive data analysis method, which has been applied extensively in other scientific studies.