Magnetic Field Controlled Difiraction Grating

A novel magnetically tunable difiraction grating based on V-shaped and magnetic nanoparticles is proposed and demonstrated experimentally. The grating's period we made was 10"m, and the grooves and the convex groove were both 5"m. The refraction index of the fer- ro∞uid is sensitive to surrounding magnetic fleld. We've demonstrated the magnetically tenability of this grating by measuring the changing of the difiraction angle of the high order difiraction light. The difiracted light was received by CCD and the movement of the laser spot, i.e., the small change of the difiraction angel was recorded. This approach is a good candidate for the following applications: magnetic sensors, magnetic controlled optical switches, modulator and so on. Difiraction gratings with periodic structures are very important optical spectral elements in optical system. The difiraction gratings are usually fabricated on the surface of planar substrate. Since the difiraction gratings is flxed and it is di-cult to change the period. However in some cases, the difiraction property, i.e., the difiraction angle of a light beam with particular wavelength, is required to be adjustable. There's one device called acousto-optic modulator (1) is developed to fulflll this requirement. In this paper we have proposed another novel tunable difiraction grating with the help of the ferro∞uid. Ferro∞uid is a kind of stable colloidal suspension of ferromagnetic nanoparticles in a liquid carrier. These ferromagnetic colloids are usually dispersed by difierent kinds of surfactant (2). This material can be applied to various modern technology flelds, e.g., optical transmission (3), magneto-optical (4), optical switches (5) and thermo-optical (6,7). One of the most fascinating application of ferro∞uid used as optical device should be MF tunable optical grating (8) and shows an increasingly important role in wide range of potential applications. Up to date, there are few reports on the magnetic fleld sensor based on tunable optical grating. Such research done by Shengli Pu etal. (9), they developed a MF grating with photoresist and ferromagnetic interphase and found that the transfer of the energy of the 0th-order difiracted light to that of the higher- order is apparent. Hongzhu Ji etal. (10) also investigated direction of the emergent light after the V-shaped groove fllled with magnetic ∞uid which is related to the strength of the externally applied magnetic fleld. In this paper, we have developed another tunable difiraction grating based on V-shaped groove fllled with ferro∞uid. When the strength of the around it changes we could clearly observe the change of the difiraction angle and the movement of difiraction light beams.