We introduce multilayer structures with the phase-change material (PCM) germanium-antimony-tellurium (GST) for use as broadband switchable absorbers in the infrared wavelength range. We use a memetic optimization algorithm to optimize both the material composition and the layer thicknesses of the structures. We show that in the optimized structures near perfect absorption can be switched to very low absorption in a broad wavelength range by switching GST from its crystalline to its amorphous phase. In addition, we show that our design approach can be used for switchable radiative cooling based on PCMs. We also introduce multilayer structures based on PCMs for reconfigurable structural color generation. These structures generate multiple colors within a single pixel by switching between the two phases of the PCM. Our design approach leads to maximally distinct colors with large distances between them on the International Commission on Illumination (CIE) chromaticity diagram. Our optimized lithography-free structures have better performance than harder-to-fabricate three-dimensional structures. Our results could pave the way to novel switchable absorbers and multicolor pixels.
We introduce multilayer structures with the phase-change material germanium-antimony-tellurium (GST) for use as broadband switchable absorbers in the infrared wavelength range. We use a memetic optimization algorithm coupled with the transfer-matrix method to optimize both the material composition and the layer thicknesses of the multilayer structures. We show that in the optimized structures near perfect absorption can be switched to very low absorption in a broad wavelength range by switching GST from its crystalline to its amorphous phase. Our results could pave the way to a new class of broadband switchable absorbers and thermal sources in the infrared wavelength range.
We introduce a nanoplasmonic isolator consisting of a cavity coupled to a metal-dielectric-metal (MDM) waveguide. The waveguide and cavity are filled with a magneto-optical (MO) material, and the structure is under a static magnetic field. We show that, when MO activity is present, the cavity becomes a traveling wave resonator with unequal decay rates into the forward and backward directions. As a result, the structure operates as an isolator. We also introduce non-Hermitian plasmonic waveguide-cavity systems with topological edge states (TESs) at singular points. The structure unit cells consist of an MDM waveguide side-coupled to MDM stub resonators with modulated distances between adjacent stubs. In such structures the modulated distances introduce an effective gauge magnetic field. We show that such structures achieve extremely high sensitivity of the reflected light intensity. TESs at singular points could lead to singularity-based plasmonic devices with enhanced performance.
While several approaches have been proposed to optimize the geometrical dimensions of multilayer photonic nanostructures with a given material composition, very few works have considered simultaneously optimizing the material composition and dimensions of such nanostructures. Here, we develop a hybrid optimization algorithm as a method to design optimal multilayer photonic structures. Leveraging recent progress in metaheuristic optimization, we develop an optimization method consisting of a Monte Carlo simulation, a continuous adaptive genetic algorithm, and a pattern search algorithm. We first perform a Monte Carlo simulation over the entire design space. Structures are ranked according to the chosen fitness function. We find that this method yields viable material compositions. The material compositions of the best structures are used to parameterize the genetic algorithm in the next stage. A number of genetic algorithm populations are generated, one for each material composition, to optimize the thicknesses. These populations are run in parallel for a number of generations, evaluating the structures of each generation and using the characteristics of those that best satisfy the fitness function to improve other structures. The resulting populations converge towards the optimum of their solution space typically after a few thousand generations. The genetic algorithm used is continuous because parameters are treated as real numbers rather than bit strings as in classical genetic algorithms, and adaptive because the algorithm uses characteristics of the population pool to guide optimization. Finally, we apply a pattern search local optimization algorithm to the best result from each population to find the exact optimum.
In the lore of quantum metrology, one often hears (or reads) the following no-go theorem: If you put a vacuum into one input port of a balanced Mach-Zehnder interferometer, then no matter what you put into the other input port, and no matter what your detection scheme, the sensitivity can never be better than the shot-noise limit (SNL). Often the proof of this theorem is cited to be in C. Caves, Phys. Rev. D 23, 1693 (1981), but upon further inspection, no such claim is made there. Quantum-Fisher-information-based arguments suggestive of this no-go theorem appear elsewhere in the literature, but are not stated in their full generality. Here we thoroughly explore this no-go theorem and give a rigorous statement: the no-go theorem holds whenever the unknown phase shift is split between both of the arms of the interferometer, but remarkably does not hold when only one arm has the unknown phase shift. In the latter scenario, we provide an explicit measurement strategy that beats the SNL. We also point out that these two scenarios are physically different and correspond to different types of sensing applications.
Recently, cylindrical vector beams have drawn considerable attention for their interesting
properties and potential applications in super-resolution optical imaging, optical trapping and
manipulating. It’s easy to obtain inhomogeneous status of polarization by designing the diffractive
optical elements particularly. With the change of the polarization of cylindrical vector beams, three dimensional (3D) flattop fields could be obtained. Numerical analysis shows that the full width at half
maximum of the proposed 3D flattop light field is nearly 5λ for axial distributions. The result shows a
potential application of the cylindrical vector beams in laser beam shaping system and laser cutting.
The focusing properties of vector beams have attracted great attention and quickly became the
subject of extensive worldwide research due to their applications in lithography, optical storage,
microscopy, material processing, and optical trapping. Focusing properties of the radially polarized
beam and generalized cylindrical vector beams in high numerical aperture system with designed pure
phase filter are analyzed in detail by using vector Debye diffraction theory. By utilizing diffractive
optical element to partly change the polarization of vector beams, the energy density of light field in the
vicinity of focus is studied by the numerical analysis. Numerical simulation result shows that optical
bubbles can be obtained by changing the composition and polarization of the incident beams. At last,
optical tweezers are constituted by two optical bubbles around the focus.
This article deals with designing broadband and high efficiency metal multi-layer dielectric grating (MMDG) used to
compress and stretch ultra-short laser pulse. The diffraction characteristics of MMDG are analyzed with the method of
rigorous coupled-wave analysis (RCWA). Taking the diffraction efficiency of the -1 order as the value of merit function,
the parameters such as groove depth, residual thickness, duty cycle are optimized to obtain broadband and high
diffraction efficiency. The optimized MMDG shows an ultra-broadband working spectrum with the average efficiency
exceeding 97% over 135nm wavelength centered at 800nm and TE polarization. The optimized MMDG should be useful
for chirped pulse amplification.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.