Optical nonlinearities, such as thermo-optic mechanisms and free-carrier dispersion, are often considered unwelcome effects in silicon-based resonators and, more specifically, optomechanical ...cavities, since they affect, for instance, the relative detuning between an optical resonance and the excitation laser. Here, we exploit these nonlinearities and their intercoupling with the mechanical degrees of freedom of a silicon optomechanical nanobeam to unveil a rich set of fundamentally different complex dynamics. By smoothly changing the parameters of the excitation laser we demonstrate accurate control to activate two- and four-dimensional limit cycles, a period-doubling route and a six-dimensional chaos. In addition, by scanning the laser parameters in opposite senses we demonstrate bistability and hysteresis between two- and four-dimensional limit cycles, between different coherent mechanical states and between four-dimensional limit cycles and chaos. Our findings open new routes towards exploiting silicon-based optomechanical photonic crystals as a versatile building block to be used in neurocomputational networks and for chaos-based applications.
Radiationless anapole states in on-chip photonics Díaz-Escobar, Evelyn; Bauer, Thomas; Pinilla-Cienfuegos, Elena ...
Light, science & applications,
10/2021, Letnik:
10, Številka:
1
Journal Article
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Abstract
High-index nanoparticles are known to support radiationless states called anapoles, where dipolar and toroidal moments interfere to inhibit scattering to the far field. In order to exploit ...the striking properties arising from these interference conditions in photonic integrated circuits, the particles must be driven in-plane via integrated waveguides. Here, we address the excitation of electric anapole states in silicon disks when excited on-chip at telecom wavelengths. In contrast to normal illumination, we find that the anapole condition—identified by a strong reduction of the scattering—does not overlap with the near-field energy maximum, an observation attributed to retardation effects. We experimentally verify the two distinct spectral regions in individual disks illuminated in-plane from closely placed waveguide terminations via far-field and near-field measurements. Our finding has important consequences concerning the use of anapole states and interference effects of other Mie-type resonances in high-index nanoparticles for building complex photonic integrated circuitry.
In this work, we report numerical simulations and experiments of the optical response of a gold nanostrip embedded in a silicon strip waveguide gap at telecom wavelengths. We show that the spectral ...features observed in transmission and reflection when the metallic nanostructure is inserted in the gap are extremely different than those observed in free-space excitation. First, we find that interference between the guided field and the electric dipolar resonance of the metallic nanostructure results in high-contrast (> 10) spectral features showing an asymmetric Fano spectral profile. Secondly, we reveal a crossing in the transmission and reflection responses close to the nanostructure resonance wavelength as a key feature of our system. This approach, which can be realized using standard semiconductor nanofabrication tools, could lead to a full exploitation of the extreme properties of subwavelength metallic nanostructures in an on-chip configuration, with special relevance in fields such as biosensing or optical switching.
LiDAR sensors are widely used in many areas and, in recent years, that includes agricultural tasks. In this work, a self-developed mobile terrestrial laser scanner based on a 2D light detection and ...ranging (LiDAR) sensor was used to scan an intensive olive orchard, and different algorithms were developed to estimate canopy volume. Canopy volume estimations derived from LiDAR sensor readings were compared to conventional estimations used in fruticulture/horticulture research and the results prove that they are equivalent with coefficients of correlation ranging from
r
= 0.56 to
r
= 0.82 depending on the algorithms used. Additionally, tools related to analysis of point cloud data from the LiDAR-based system are proposed to extract further geometrical and structural information from tree row crop canopies to be offered to farmers and technical advisors as digital raster maps. Having high spatial resolution information on canopy geometry (i.e., height, width and volume) and on canopy structure (i.e., light penetrability, leafiness and porosity) may result in better orchard management decisions. Easily obtainable, reliable information on canopy geometry and structure may favour the development of decision support systems either for irrigation, fertilization or canopy management, as well as for variable rate application of agricultural inputs in the framework of precision fruticulture/horticulture.
Passion fruit rind is a by-product rich in bioactive compounds that can be recovered by high pressure extractions and ultrasound using nontoxic solvents in shorter process times. This work ...investigated Pressurized Liquid Extraction (PLE) and its combination with ultrasound (Ultrasound-Assisted Pressurized Liquid Extraction, UAPLE) to intensify the recovery of phenolic compounds from passion fruit rinds. The influences of process parameters such as temperature, pressure, ultrasonic intensity and solvent mass flow rate on the global yield (X0), total phenolic content (TPC) and antioxidant capacity were evaluated. The major phenolics were determined by UHPLC-QE HRMS. Kinetic extraction curves adjusted by the Spline and two-site models showed that in UAPLE (60 °C, 10 MPa and 360 W/cm2) with solvent flow rate of 10 g/min, 100% of TPC was recovered in 68.54 min of extraction. This condition also provided the greatest economic viability concerning total phenolics, with the lowest estimated manufacturing cost.
Synthetic compounds in processed food have been increasingly rejected by consumers, who look for natural compounds that promote health benefits and are obtained with sustainable technologies. The bioactive compounds found in passion fruit rinds can meet this industrial demand as potential colorants, additives and natural preservatives in foods or beverages, incorporated in cosmetics, functional food and pharmaceutical supplements. In order to successfully recover bioactive compounds, it is recommended to apply selective extraction techniques in the target compound, thus providing final products with greater added value. In addition, the process optimization is crucial to achieve optimal extraction conditions to maximize the yield of the targent compounds. Given this context, searching for a more sustainable destination of the passion fruit agroindustrial waste and to increase its commercial value, this work proposes the combination of two extraction techniques, Ultrasound and Pressurized Liquid Extraction (UAPLE), to intensify the recovery of bioactive compounds from passion fruit rinds. The findings of this work reveal that UAPLE can enhance the extraction of phenolic compounds from passion fruit rinds even at moderate temperatures, thus encouraging the application of this technique for other agroindustrial by-products. Moreover, the economic evaluation of the UAPLE at the optimal conditions indicates its viability for industrial scale application.
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•In UAPLE, total phenolics were 100% greater than in PLE under the same conditions.•Ultrasonic intensity above 240 W/cm2 increased yield of total phenolics in UAPLE.•Optimized solvent mass flow rate at UAPLE was 10 g/min in 68.54 min of extraction.•Isoorientin, vicenin, vitexin, orientin, isovitexin were identified and quantified.•Pressurized liquid extraction combined to ultrasound intensifies phenolics recovery.
Catecholamine‐triggered β‐adrenoceptor (β‐AR) signaling is essential for the correct functioning of the heart. Although both β1‐ and β2‐AR subtypes are expressed in cardiomyocytes, drugs selectively ...targeting β1‐AR have proven this receptor as the main target for the therapeutic effects of beta blockers in the heart. Here, we report a new strategy for the light‐control of β1‐AR activation by means of photoswitchable drugs with a high level of β1‐/β2‐AR selectivity. All reported molecules allow for an efficient real‐time optical control of receptor function in vitro. Moreover, using confocal microscopy we demonstrate that the binding of our best hit, pAzo‐2, can be reversibly photocontrolled. Strikingly, pAzo‐2 also enables a dynamic cardiac rhythm management on living zebrafish larvae using light, thus highlighting the therapeutic and research potential of the developed photoswitches. Overall, this work provides the first proof of precise control of the therapeutic target β1‐AR in native environments using light.
New azobenzene‐based molecular photoswitches active for the therapeutic β1‐adrenoceptor (β1‐AR) are presented. The most promising candidate, named pAzo‐2, has a potency and β1/β2 selectivity similar to approved beta blockers. Importantly, pAzo‐2 is compatible with imaging techniques and its potential as a cardioselective light‐controlled drug has been validated by the reversible photomodulation of the cardiac rhythm in living zebrafish larvae.
Plasmonic resonances in metallic nanostructures provide a way for broadband enhanced light-matter interaction in subwavelength regions, which can be used to boost a variety of physical phenomena, ...notably including Raman scattering. Such nanostructures can be integrated on silicon chips and driven via dielectric waveguides, which may improve the performance of photonic integrated circuits in terms of foot-print, efficiency, sensitivity or power consumption, amongst other figures of merit. Here, we show that an isolated plasmonic nanoantenna can be efficiently integrated into a silicon nitride waveguide to detect surface-enhanced Raman scattering (SERS) spectra from molecular monolayers. We study numerically and experimentally two different configurations, both enabling the recording of Raman spectra at the output: nanoantenna on top of the waveguide and nanoantenna inserted in a subwavelength gap built in the waveguide. We also compare both configurations, which may pave the way toward massive integration of SERS devices for lab-on-a-chip applications.
Cavity optomechanics has recently emerged as a new paradigm enabling the manipulation of mechanical motion via optical fields tightly confined in deformable cavities. When driving an optomechanical ...(OM) crystal cavity with a laser blue-detuned with respect to the optical resonance, the mechanical motion is amplified, ultimately resulting in phonon lasing at MHz and even GHz frequencies. In this work, we show that a silicon OM crystal cavity performs as an OM microwave oscillator when pumped above the threshold for self-sustained OM oscillations. To this end, we use an OM cavity designed to have a breathing-like mechanical mode at 3.897 GHz in a full phononic bandgap. Our measurements show that the first harmonic of the detected signal displays a phase noise of ≈−100 dBc/Hz at 100 kHz. Stronger blue-detuned driving leads eventually to the formation of an OM frequency comb, whose lines are spaced by the mechanical frequency. We also measure the phase noise for higher-order harmonics and show that, unlike in Brillouin oscillators, the noise is increased as corresponding to classical harmonic mixing. Finally, we present real-time measurements of the comb waveform and show that it can be fitted to a theoretical model recently presented. Our results suggest that silicon OM cavities could be relevant processing elements in microwave photonics and optical RF processing, in particular in disciplines requiring low weight, compactness and fiber interconnection.
Abstract
Catecholamine‐triggered β‐adrenoceptor (β‐AR) signaling is essential for the correct functioning of the heart. Although both β
1
‐ and β
2
‐AR subtypes are expressed in cardiomyocytes, drugs ...selectively targeting β
1
‐AR have proven this receptor as the main target for the therapeutic effects of beta blockers in the heart. Here, we report a new strategy for the light‐control of β
1
‐AR activation by means of photoswitchable drugs with a high level of β
1
‐/β
2
‐AR selectivity. All reported molecules allow for an efficient real‐time optical control of receptor function in vitro. Moreover, using confocal microscopy we demonstrate that the binding of our best hit, pAzo‐2, can be reversibly photocontrolled. Strikingly, pAzo‐2 also enables a dynamic cardiac rhythm management on living zebrafish larvae using light, thus highlighting the therapeutic and research potential of the developed photoswitches. Overall, this work provides the first proof of precise control of the therapeutic target β
1
‐AR in native environments using light.
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