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Register a new userAll-dielectric one-dimensional periodic structures for total omnidirectional reflection and partial spontaneous emission control
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A remarkable property of one-dimensional all-dielectric periodic structures has recently been reported, namely a one-dimensional lattice can totally reflect electromagnetic wave of any polarization at all angles within a prescribed frequency region. Unlike their metallic counterpart, such all-dielectric omnidirectional mirrors are nearly free of loss at optical frequencies. Here we discuss the physics, design criteria and applications of the thin-film all-dielectric omnidirectional mirror. The experimental demonstration of the mirror is presented at optical frequencies.
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We show that under certain conditions one-dimensional dielectric lattice possesses total omnidirectional reflection of incident light. The predictions are verified experimentally using Na3AlF6/ZnSe multilayer structure developed by means of standard optical technology. The structure was found to exhibit reflection coefficient more then 99% in the range of incident angles 0-86 (degree) at the wavelength of 632.8 nm for s-polarization. The results are believed to stimulate new experiments on photonic crystals and controlled spontaneous emission.
It is shown that total reflection for all incident angles does not require a two- or three-dimensional photonic crystal. We demonstrate that a one-dimensional photonic crystal can exhibit total omni-directional reflection for any incident wave within some frequency region. The formation of the omni-directional gap is discussed and a wide range of realistic fabrication parameters is proposed.
We consider a one-dimensional model allowing analytical derivation of the effective interactions between two charged colloids. We evaluate exactly the partition function for an electroneutral salt-free suspension with dielectric jumps at the colloids position. We derive a contact relation with the pressure that shows there is like-charge attraction, whether or not the counterions are confined between the colloids. In contrast to the homogeneous dielectric case, there is the possibility for the colloids to attract despite the number of counter-ions ($N$) being even. The results are shown to recover the mean-field prediction in the limit $Nto infty$.
Periodic arrays of air nanoholes in thin metal films that support surface plasmon resonances can provide an alternative approach for boosting the light-matter interactions at the nanoscale. Indeed, nanohole arrays have garnered great interest in recent years for their use in biosensing, light emission enhancement and spectroscopy. However, the large-scale use of nanohole arrays in emerging technology requires new low-cost fabrication techniques. Here, we demonstrate a simple technique to fabricate nanohole arrays and examine their photonic applications. In contrast to the complicated and most commonly used electron beam lithography technique, hexagonal arrays of nanoholes are fabricated by using a simple combination of shadowing nanosphere lithography technique and electron beam deposition. These arrays are shown to offer enhancements in the lasing emission of an organic dye liquid gain medium with a quality factor above 150. Additionally, a 7-fold increase in Purcell factor is observed for CdSe quantum dot-integrated nanohole arrays.
While practical realizations of optical invisibility have been achieved so far by various ingenious methods, they generally rely on complex materials which prevent the wide implementation of such schemes. Here, we propose an alternative indivisibility procedure to design objects (i.e. self-cloaked structures) that have optical properties identical to the surrounding environment and are, thereby, intrinsically invisible to an external observer as such (without the necessity of an external cloak). The proposed method is based on the uncoupling of the scattered waves from the incident radiation by judiciously manipulating the scattering potential of a given object. We show that such a procedure is able to yield optical invisibility for any arbitrarily shaped object within any specified frequency bandwidth by simply employing isotropic non-magnetic dielectric materials, without the usage of loss or gain material. The validity of the design principle has been verified by direct experimental observations of the spatial electric field profiles and scattering patterns at the microwave regime. Our alternative self-cloaking strategy may have profound implications especially in noninvasive probing and cloaked sensor applications, where the wave penetrability into the sensor region is essential together with its invisibility to minimize the field distortion.
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