© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim 1 wileyonlinelibrary.com COMMUNICATION www.MaterialsViews.com www.advopticalmat.de A bidispersed magnetic colloid containing micrometer-sized magnetizable spheres and nanomagnetic particles is an inter- esting as well as intriguing scattering medium. [1–3] Optical wave propagation in strongly scattering media or in partially ordered systems exhibit several novel and useful phenomena. Strong and weak localization, photonic Hall effects, and anisotropic dif- fusion coefficients are some examples. [4–6] The most fascinating phenomenon amongst these is that of the storage and retrieval of light. [7–9] Successful attempts were also made to transport the stored light some distance: [10] Scully and his group have trapped laser signals (with help of a writer pulse) in ultra-cold rubidium atoms10. Then the writer laser was switched off. After a frac- tion of millisecond, another reader laser was switched on which was at a distance of 6 millimeters away from the writer laser, and the signal pulse was received. We demonstrate here a new technique which is comparatively simpler, cost effective, and which operates at room temperature. In most of the above examples, scatterers were nonmagnetic particles surrounded by a nonmagnetic medium. When scat- terers are magnetic or the surrounding medium is magnetically active, they exhibit new photonic effects. [11–14] When both the scatterers as well as the medium are magnetizable, the system manifests several intriguing possibilities. We show here that such a scattering system can transport the stored light some distance. Previously, we showed that such a ferrodispersion exhibits several magnetically tunable photonic effects like weak localization, zero scattering, photonic bandgaps, optical capaci- tors, etc. [15–19] The most intriguing effect is the trapping and release of light with the help of an externally applied magnetic field. [15] The experiment was performed with the following con- figuration: linearly polarized light was allowed to pass through a diluted sample of magnetizable micrometer-sized spheres (MMS). The latter was subjected to a static magnetic field. It was observed that when the direction of propagation and the electric vector of the incident light are transverse to the direc- tion of the applied field, the emergent light from the sample disappears at a critical value of the magnetic field. The light reappears when the field is slightly more or less than this value. The system was then subjected to the critical field and was exposed to the incident light for some time and then the light shutter was closed. Under this condition, the field was switched off. Almost immediately, a flash of light with the same frequency and state of polarization as that of the incident light was observed. The findings were attributed to the trap- ping of light at the critical field and its release when the field was removed. The details of these findings are described else- where. [15] In the present work, we show that the trapped light can be carried some distance and retrieved at this distance. We have also studied the role of the size of the MMS, the wave- length of incident light, and the exposure time, and results are analyzed in terms of morphology-dependent resonance (MDR) induced by the applied magnetic field. Methods of preparation of stable suspensions of micrometer- sized magnetite particles and the ferrofluid are described in earlier papers. [13,16] Commercially available magnetite powder was first washed with dilute nitric acid to remove impurities. The powder was then washed with double-distilled water and acetone. The dried powder was mixed with kerosene and ball- milled in the presence of oleic acid. Using fractional sedimen- tation, suspensions containing 1, 2, and 3 μm-sized particles were obtained. The particles were found to be almost spherical. Ferrofluid was synthesized by co-precipitating nanomagnetic particles of magnetite and coating these particles with oleic acid. Again kerosene was used as a base liquid. Aggregation, if any, was removed by centrifuging the fluid at 12 000 rpm. The average particle size of the nanomagnetic particles was deter- mined using X-ray diffraction and was found to be ∼10 nm. Saturation magnetization of the fluid was 200 Gauss. Each sus- pension of MMS was mixed with the ferrofluid and diluted with kerosene as per the requirement. These samples were homog- enized by ultrasonification and no sedimentation was observed during the experimental measurements. The sample under investigation was poured into a rectangular glass cell with a 2 mm path length. All the samples were found to be trans- parent at this path length. The schematic of the experimental setup is shown in Figure 1 a. A 5 mW diode pumped solid state (DPSS) green laser ( λ = 532 nm) and a He–Ne 10 mW laser ( λ = 632 μm) were used as light sources. A Glan–Thomson polarizing prism was used to convert unpolarized light into polarized light and the axis of the polarizer was arranged so that E-vector of the light incident on the glass cell remained perpendicular to the direction of the applied field. An electromagnet was driven by a constant current power supply. The magnetic field was measured using a Hall probe. The rectangular cell filled with the ferrodispersion was fixed between the pole pieces of the magnet and was mounted on an x-y-z platform, and its posi- tion could be read by a micrometer screw. The translation of the stage in the direction of the magnetic field was controlled by a motor. Emerging light from the sample was detected by a CCD camera. This camera was also mounted on a translation stage. Provision was made to introduce another glass cell of 1 cm path DOI: 10.1002/adom.201300123 Experimental Demonstration of Magnetic Carriage for Transport of Light Trapped in Magnetizable Mie Spheres Rajesh Patel, and Rasbindu V. Mehta* Prof. R. Patel, Prof. R. V. Mehta Department of Physics Maharaja Krishnakumarsinhji Bhavnagar University Bhavnagar, 364002, India E-mail: rvm@bhavuni.edu Adv. Optical Mater. 2013, DOI: 10.1002/adom.201300123