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Chaotic resonators constructed from planar silicon-on-insulator photonic crystals and deformed polystyrene microspheres are demonstrated to store up to six times more light energy than their classical, non-chaotic counterparts. This effect is attributed to the modification of the trajectories and lifetimes of photons in the cavity.

Aiming at the problem of the object tracking algorithm based on a single feature which can’t track the object in the complex cases accurately, this paper proposes an object tracking algorithm based on global SURF feature. Because the color feature is invariant to rotating and deformation, SURF feature has a good robustness to illumination change, a certain degree of angle change, it fuses the two features to from a new feature called global SURF feature. Then, it creates the object model based on global SURF feature, combines with particle filter algorithm and updates the object template and feature points dynamically in the process of tracking. Finally, it realizes the accurate tracking for the object. The experimental results in different settings show that it has a good real-time and high robustness which fits for the object tracking in the complex cases.

Organolead trihalide perovskites have drawn substantial interest for photovoltaic and optoelectronic applications due to their remarkable physical properties and low processing cost. However, perovskite thin films suffer from low carrier mobility as a result of their structural imperfections such as grain boundaries and pinholes, limiting their device performance and application potential. Here we demonstrate a simple and straightforward synthetic strategy based on coupling perovskite films with embedded single-walled carbon nanotubes. We are able to significantly enhance the hole and electron mobilities of the perovskite film to record-high values of 595.3 and 108.7 cm2 V-1 s-1 , respectively. Such a synergistic effect can be harnessed to construct ambipolar phototransistors with an ultrahigh detectivity of 3.7 × 1014 Jones and a responsivity of 1 × 104 A W-1 , on a par with the best devices available to date. The perovskite/carbon nanotube hybrids should provide a platform that is highly desirable for fields as diverse as optoelectronics, solar energy conversion, and molecular sensing.

We developed a blackbody system based on gold nanoparticles with broad band absorption, which can be utilized as emitters for a new type of light source and perfect absorbers in high-efficiency on-site water desalination.

Chaos is a complex dynamics with exponential sensitivity to the initial conditions. Since the study of three-body problem by Henri Poincare, chaos has been extensively studied in many systems, ranging from electronics to fluids, brains and more recently photonics. Chaos is a ubiquitous phenomenon in Nature, from the gigantic oceanic waves to the disordered scales of white beetles at nanoscale. The presence of chaos is often unwanted in applications, as it introduces unpredictability,which makes it difficult to predict or explain experimental results. Inspired by how chaos permeates the natural world, this thesis investigates on how the interaction between light and chaotic structure can enhance the performance of photonics devices. With a proper design of the lighter-mater interaction in chaotic resonators, I illustrate how chaos can be used to enhance the ability of an optical cavity to store electromagnetic energy, realize a blackbody system composed of gold nanoparticles, localize light beyond the diffraction limit and control the phase transition of super-radiance.

Asymmetric nanocrystals have practical significance in nanotechnologies but present fundamental synthetic challenges. Thiol ligands have proven effective in breaking the symmetric growth of metallic nanocrystals but their exact roles in the synthesis remain elusive. Here, we synthesized an unprecedented Au nanorod–Au nanoparticle (AuNR–AuNP) dimer structure with the assistance of a thiol ligand. On the basis of our experimental observations, we unraveled for the first time that the thiol could cause an inhomogeneous distribution of surface strains on the seed crystals as well as a modulated reduction rate of metal precursors, which jointly induced the asymmetric growth of monometallic dimers.

Colloidal metal nanocrystals with strong, stable, and tunable localized surface plasmon resonances (SPRs) can be useful in a corrosive environment for many applications including field-enhanced spectroscopies, plasmon-mediated catalysis, etc. Here, a new synthetic strategy is reported that enables the epitaxial growth of a homogeneously alloyed AuAg shell on Au nanorod seeds, circumventing the phase segregation of Au and Ag encountered in conventional synthesis. The resulting core-shell structured bimetallic nanorods (AuNR@AuAg) have well-mixed Au and Ag atoms in their shell without discernible domains. This degree of mixing allows AuNR@AuAg to combine the high stability of Au with the superior plasmonic activity of Ag, thus outperforming seemingly similar nanostructures with monometallic shells (e.g., Ag-coated Au NRs (AuNR@Ag) and Au-coated Au NRs (AuNR@Au)). AuNR@AuAg is comparable to AuNR@Ag in plasmonic activity, but that it is markedly more stable toward oxidative treatment. Specifically, AuNR@AuAg and AuNR@Ag exhibit similarly strong signals in surface-enhanced Raman spectroscopy that are some 30-fold higher than that of AuNR@Au. When incubated with a H(2)O(2) solution (0.5 m), the plasmonic activity of AuNR@Ag immediately and severely decayed, whereas AuNR@AuAg retained its activity intact. Moreover, the longitudinal SPR frequency of AuNR@AuAg can be tuned throughout the red wavelengths (≈620-690 nm) by controlling the thickness of the AuAg alloy shell. The synthetic strategy is versatile to fabricate AuAg alloyed shells on different shaped Au, with prospects for new possibilities in the synthesis and application of plasmonic nanocrystals.

This work is supported by Kaust (Award No. CRG-1-2012-FRA-005), by NanoNextNL of the Dutch ministry EL&I and 130 partners and by the EU FET project ‘SPANGL4Q’. Hurricanes, tsunamis, rogue waves and tornadoes are rare natural phenomena that embed an exceptionally large amount of energy, which appears and quickly disappears in a probabilistic fashion. This makes them difficult to predict and hard to generate on demand. Here we demonstrate that we can trigger the onset of rare events akin to rogue waves controllably, and systematically use their generation to break the diffraction limit of light propagation. We illustrate this phenomenon in the case of a random field, where energy oscillates among incoherent degrees of freedom. Despite the low energy carried by each wave, we illustrate how to control a mechanism of spontaneous synchronization, which constructively builds up the spectral energy available in the whole bandwidth of the field into giant structures, whose statistics is predictable. The larger the frequency bandwidth of the random field, the larger the amplitude of rare events that are built up by this mechanism. Our system is composed of an integrated optical resonator, realized on a photonic crystal chip. Through near-field imaging experiments, we record confined rogue waves characterized by a spatial localization of 206 nm and with an ultrashort duration of 163 fs at a wavelength of 1.55 μm. Such localized energy patterns are formed in a deterministic dielectric structure that does not require nonlinear properties. Postprint

We acknowledge support from the EPSRC (ADF, Fellowships No. EP/I004602/1 and No. EP/J004200/1) and KAUST (AF, Grant No. CRG-1-2012-FRA-005). We show here theoretically and experimentally how chaotic Photonic Crystal resonators can be used for en- ergy harvesting applications and the demonstration of fundamental theories, like the onset of superradiance in quantum systems. Publisher PDF

By using theory and experiments, we investigate a new mechanism based on spontaneous synchronization of random waves which generates ultrafast subwavelength rare events in integrated photonic chips.

We experimentally investigate the Dicke phase transition in chaotic optical resonators realized with two-dimensional photonics crystals. This setup circumvents the constraints of the system originally investigated by Dicke and allows a detailed study of the various properties of the superradiant transition. Our experimental results, analytical prediction, and numerical modeling based on random-matrix theory demonstrate that the probability density \ud We experimentally investigate the Dicke phase transition in chaotic optical resonators realized with two-dimensional photonics crystals. This setup circumvents the constraints of the system originally investigated by Dicke and allows a detailed study of the various properties of the superradiant transition. Our experimental results, analytical prediction, and numerical modeling based on random-matrix theory demonstrate that the probability density P(Γ) of the resonance widths provides a new criterion to test the occurrence of the Dicke transition.

By combining analytic theory, parallel ab-initio simulations and experiments, we demonstrate how to exploit chaos to dramatically enhance light trapping performance.

We observed the phase transition of multiple superradiant states in chaotic optical cavities with multiple open decay channels base on photonic crystals.

The harvesting of solar radiation for steam generation has drawn wide attention as a future sustainable technology for the renewable production of clean water worldwide. Here, a new super-dark metasurface of 200 nm thickness is presented, which reaches a solar thermal efficiency of 87% when exposed to an intensity of only 2.3 sun, maintaining a stable efficiency of 90% at higher solar intensities. The metasurface is composed of extremely robust nanoparticles, which are up to 98% recyclable and can be produced on massively large scales by wet chemistry. By employing such reusable nanoparticles on an area of 1 m2, 1.2 kg of seawater can be purified within only 1 h under natural sunshine. With such excellent performances, this nanomaterial can open new applications of high-performance solar steam.

To investigate the clinical efficacy of laparoscopic ventriculoperitoneal shunt with temporary external drainage in the treatment of hydrocephalus.Fifty-two cases of hydrocephalus randomized into two groups to receive laparoscopic assisted ventriculoperitoneal shunt with temporary external drainage (19 male and 7 female patients) and conventional ventriculoperitoneal shunt (20 male and 6 female patients). The catheterization time in the abdominal cavity, release time of intracranial hypertension, average hospital stay, postoperative pains, and postoperative complications were compared between the two groups.Laparoscopic ventriculoperitoneal shunt with temporary external drainage was performed successfully in all the cases without intraoperative conversion to open surgery. Compared with the conventional ventriculoperitoneal shunt, laparoscopic ventriculoperitoneal shunt with temporary external drainage was associated with significantly shortened catheterization time in the abdominal cavity, release time of intracranial hypertension, and average hospital stay (P0.01) as well as lowered postoperative pain score at 4, 8, 16, and 24 h after the operation. The pain scores at 48 and 72 h postoperatively were comparable between the two groups. During the follow-up 3 months, the patients receiving laparoscopic ventriculoperitoneal shunt were found to have significantly lower rates of peritoneal end obstruction and abdominal cavity infection than those having conventional shunt (3.8% vs 19.2%, P0.01; 1.0% vs 23.1%, P0.01).Laparoscopic ventriculoperitoneal shunt with temporary external drainage is feasible and produces better clinical therapeutic effect for management of hydrocephalus.

Changxu Liu and Jianfeng Huang reflect on their experiences of a collaborative research project that was at a crossroads between physics and chemistry.

Plasmonic nanoparticles are ideal candidates for hot-electron-assisted applications, but their narrow resonance region and limited hotspot number hindered the energy utilization of broadband solar energy. Inspired by tree branches, we designed and chemically synthesized silver fractals, which enable self-constructed hotspots and multiple plasmonic resonances, extending the broadband generation of hot electrons for better matching with the solar radiation spectrum. We directly revealed the plasmonic origin, the spatial distribution, and the decay dynamics of hot electrons on the single-particle level by using ab initio simulation, dark-field spectroscopy, pump-probe measurements, and electron energy loss spectroscopy. Our results show that fractals with acute tips and narrow gaps can support broadband resonances (400-1100 nm) and a large number of randomly distributed hotspots, which can provide unpolarized enhanced near field and promote hot electron generation. As a proof-of-concept, hot-electron-triggered dimerization of p-nitropthiophenol and hydrogen production are investigated under various irradiations, and the promoted hot electron generation on fractals was confirmed with significantly improved efficiency.

We investigate both theoretically and experimentally a new type of laser, which exploits a broadband light “condensation” process sustained by the stimulated amplification of an optical blackbody metamaterial.

In this work, by means of analytic theory and ab-initio simulations, the generation of rogue waves was investigated by exploiting the phenomenon of quantum chaos. In particular, the light motion under irreversible conditions is studied and a new avenue for the generation of Rogue waves in linear optical microresonators that do not possess any randomness in the refractive index is demonstrated. In these systems, light undergoes a chaotic scattering and exhibits deviations from Rayleigh distribution when suitable output channels are introduced. Deviations from Rayleigh distribution appear as a classic “L” shape tail, which is the signature of the generation of rare events in the structure. Such events manifest themselves as strongly localized Rogue waves, whose spatio-temporal structure is studied by finite difference time-domain (FDTD) simulations. This phenomenon is fully driven by chaos, and provides a novel framework to theoretically and experimentally investigate the formation or rogue waves. Quite interestingly, the process increases the coherence of light and leads to the generation of extremely localized rogue waves with subwavelength features. In particular, the formation of rogue waves whose extension is approximately 0.2*λ, with λ being the internal wavelength inside the material with the highest refractive index, was observed.