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Bio
Following its discovery at U-M in 2007, the main topic of research in Professor Rand's group is optical magnetism. Intense magnetization has been induced experimentally in a variety of transparent insulating materials by light at moderate intensities and for the first time provides a direct way to control spins in dielectric condensed matter, to separate charges for optical-electrical power conversion, and to modify the permeability of natural materials for transformation optics. Quantum theory of this unexpected phenomenon was recently published, explaining how parametric enhancement of the weak magnetic force of light leads to previously unknown magneto-electric effects under non-relativistic conditions.
Experiments on this and other topics in Professor Rand's laboratory emphasize high resolution laser spectroscopy of solids. Ultrashort pulse lasers and tunable continuous sources are the main tools used to make time-resolved and frequency-resolved measurements in new materials such as sesquioxide powders, transparent ceramics, and hybrid polymers in order to evaluate their structure-function relationships and their suitability for applications. These classes of materials are relevant both to magnetic optics and other subjects of current interest in the group, such as random lasers, wide bandwidth ceramic lasers, and nonlinear optics. Additional characterization techniques used in this research include cathodoluminescence, utilizing electron beam excitation in an ultrahigh vacuum chamber, photo-luminescence at cryogenic temperatures, coherent transient spectroscopy, and four-wave mixing. Consequently graduate students receive broad-based training in these table-top methodologies of precision optical science.
Current Research
Our research has an inter-disciplinary style and currently focuses on two frontiers of optical science:
(i) Intense magnetic phenomena in optical dielectrics, to enable modifications of refractive indices and other applications normally associated with metamaterials
(ii) Laser cooling of solids, to evaluate the prospect of cooling condensed matter to sub-Kelvin temperatures.
The first topic involves fundamental studies of magneto-optical physics of dielectric media, in a quest to demonstrate modification of refractive index behavior and new magneto-optic phenomena in ordinary materials. “Transformation optics” is a hot topic that to date have been discussed only in the context of metamaterials. However, we recently discovered intense transverse optical magnetism in homogeneous dielectrics at moderate laser intensities. Now we are pioneering methods to exploit it to achieve negative permeability and programmable refractive index changes via nonlinear optical processes. This work is opening the door to demonstrations of unanticipated magneto-optical properties in completely homogeneous, natural materials.
The second topic in our group is laser cooling of solids. While numerous groups world-wide have performed experiments demonstrating that anti-Stokes fluorescence can produce modest cooling in condensed matter, we are interested in developing techniques for solids that are as effective as those used for laser-cooling of gases. The Doppler effect which is used to great advantage in gases is absent in solids however, so improvements require entirely new concepts. To date, we have analyzed this problem thermodynamically and proven that just as for gases the most effective optical emission process for cooling is spontaneous emission, not stimulated emission. However two-step procedures that alternate between stimulated and spontaneous processes could be useful in overcoming the limitations of existing methods. Recently we analyzed a Raman cooling method that promises to maintain a constant cooling rate all the way to liquid helium temperatures. Experiments are being initiated to cool a crystalline medium to sub-Kelvin temperatures, starting from room temperature.
Experiments on this and other topics in Professor Rand's laboratory emphasize high resolution laser spectroscopy of solids. Ultrashort pulse lasers and tunable continuous sources are the main tools used to make time-resolved and frequency-resolved measurements in new materials such as sesquioxide powders, transparent ceramics, and hybrid polymers in order to evaluate their structure-function relationships and their suitability for applications. These classes of materials are relevant both to magnetic optics and other subjects of current interest in the group, such as random lasers, wide bandwidth ceramic lasers, and nonlinear optics. Additional characterization techniques used in this research include cathodoluminescence, utilizing electron beam excitation in an ultrahigh vacuum chamber, photo-luminescence at cryogenic temperatures, coherent transient spectroscopy, and four-wave mixing. Consequently graduate students receive broad-based training in these table-top methodologies of precision optical science.
Current Research
Our research has an inter-disciplinary style and currently focuses on two frontiers of optical science:
(i) Intense magnetic phenomena in optical dielectrics, to enable modifications of refractive indices and other applications normally associated with metamaterials
(ii) Laser cooling of solids, to evaluate the prospect of cooling condensed matter to sub-Kelvin temperatures.
The first topic involves fundamental studies of magneto-optical physics of dielectric media, in a quest to demonstrate modification of refractive index behavior and new magneto-optic phenomena in ordinary materials. “Transformation optics” is a hot topic that to date have been discussed only in the context of metamaterials. However, we recently discovered intense transverse optical magnetism in homogeneous dielectrics at moderate laser intensities. Now we are pioneering methods to exploit it to achieve negative permeability and programmable refractive index changes via nonlinear optical processes. This work is opening the door to demonstrations of unanticipated magneto-optical properties in completely homogeneous, natural materials.
The second topic in our group is laser cooling of solids. While numerous groups world-wide have performed experiments demonstrating that anti-Stokes fluorescence can produce modest cooling in condensed matter, we are interested in developing techniques for solids that are as effective as those used for laser-cooling of gases. The Doppler effect which is used to great advantage in gases is absent in solids however, so improvements require entirely new concepts. To date, we have analyzed this problem thermodynamically and proven that just as for gases the most effective optical emission process for cooling is spontaneous emission, not stimulated emission. However two-step procedures that alternate between stimulated and spontaneous processes could be useful in overcoming the limitations of existing methods. Recently we analyzed a Raman cooling method that promises to maintain a constant cooling rate all the way to liquid helium temperatures. Experiments are being initiated to cool a crystalline medium to sub-Kelvin temperatures, starting from room temperature.
Research Interests
Papers共 328 篇Author StatisticsCo-AuthorSimilar Experts
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Optics Expressno. 7 (2023): 11994-11994
Optical Materials (2023): 113522-113522
2022 Conference on Lasers and Electro-Optics (CLEO)pp.1-2, (2022)
Photonic Heat Engines Science and Applications III (2021): 1170207
Frontiers in Optics + Laser Science 2021 (2021)
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