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Hashemi H.,Massachusetts Institute of Technology | Zhang B.,Singapore Alliance for Research and Technology Center | Joannopoulos J.D.,Massachusetts Institute of Technology | Johnson S.G.,Massachusetts Institute of Technology
Physical Review Letters

We show that the difficulty of cloaking is fundamentally limited by delay-loss and delay-bandwidth limitations that worsen as the size of the object to be cloaked increases relative to the wavelength, using a simple model of ground-plane cloaking. These limitations must be considered when scaling experimental cloaking demonstrations up from wavelength-scale objects. © 2010 The American Physical Society. Source

Park K.-C.,Massachusetts Institute of Technology | Choi H.J.,Massachusetts Institute of Technology | Chang C.-H.,Massachusetts Institute of Technology | Chang C.-H.,North Carolina State University | And 4 more authors.
ACS Nano

Designing multifunctional surfaces that have user-specified interactions with impacting liquids and with incident light is a topic of both fundamental and practical significance. Taking cues fromnature, we use tapered conical nanotextures to fabricate the multifunctional surfaces; the slender conical features result in large topographic roughness, while the axial gradient in the effective refractive index minimizes reflection through adiabatic index-matching between air and the substrate. Precise geometric control of the conical shape and slenderness of the features as well as periodicity at the nanoscale are all keys to optimizing the multifunctionality of the textured surface, but at the same time, these demands pose the toughest fabrication challenges. Here we report a systematic approach to concurrent design of optimal structures in the fluidic and optical domains and a fabrication procedure that achieves the desired aspect ratios and periodicities with few defects and large pattern area. Our fabricated nanostructures demonstrate structural superhydrophilicity or, in combination with a suitable chemical coating, robust superhydrophobicity. Enhanced polarization-independent optical transmission exceeding 98% has also been achieved over a broad range of bandwidth and incident angles. These nanotextured surfaces are also robustly antifogging or self-cleaning, offering potential benefits for applications such as photovoltaic solar cells. © 2012 American Chemical Society. Source

Petruccelli J.C.,Massachusetts Institute of Technology | Tian L.,Massachusetts Institute of Technology | Barbastathis G.,Massachusetts Institute of Technology | Barbastathis G.,Singapore Alliance for Research and Technology Center
Optics Express

We investigate the measurement of a thin sample's optical thickness using the transport of intensity equation (TIE) and demonstrate a version of the TIE, valid for partially coherent illumination, that allows the measurement of a sample's optical path length by the removal of illumination effects. © 2013 Optical Society of America. Source

Sheppard C.J.R.,Italian Institute of Technology | Sheppard C.J.R.,Singapore Alliance for Research and Technology Center
Applied Optics

Focusing by an aberration-free cylindrical lens is analyzed in the paraxial Fresnel and Debye approximations, and expressions are given. Plots are given for the intensity in the focal region, the defocused optical transfer function (OTF), the generalized OTF, and the ambiguity function and are compared with the case of an aberration-free spherical lens. Nonparaxial lenses are also discussed. © 2013 Optical Society of America. Source

Sheppard C.J.R.,Italian Institute of Technology | Sheppard C.J.R.,Singapore Alliance for Research and Technology Center
Optics Express

Pupil filters for cylindrical (two-dimensional) focusing with extended depth of field are investigated. An important application is in generating light sheets with uniform intensity. Filters for spherical (threedimensional) focusing with a flat axial intensity, coupled with weak side lobes are also discussed. © 2013 Optical Society of America. Source

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