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We demonstrate a high-performance reconfigurable bandpass filter implemented by cascaded Sagnac loop mirror (SLM)-based coupled resonator optical waveguides (CROWs) on the silicon-on-insulator platform. By dynamic thermal tuning of the reflectivity in each SLM, the proposed filter can achieve simultaneous 3 dB bandwidth tuning from 8.50 to 20.25 GHz and a central wavelength tuning range of 216.25 GHz. A box-like filtering response with an ultra-high extinction ratio up to 70 dB and an ultra-sharp roll-off of 0.61 are observed in a 6th-order SLM-coupled resonator optical waveguide (SLM-CROW). The proposed reconfigurable SLM-CROW filter can satisfy the demand for next-generation flexible-grid WDM networks.Anapole mode is a nonradiative resonance originating from the destructive interference between co-excited Cartesian electric dipole and toroidal dipole moments. With at least two symmetric circulating currents, the anapole mode in all-dielectric nanoresonators provides the opportunity to operate the double perfect electric conductor (PEC) mirror effects. In this work, unlike the conventional metal-dielectric-metal (MDM) nanostructure generating a plasmonic magnetic resonance, two metal components are employed to produce the fictitious images of the middle dielectric, and the whole system can thus excite the doubly mirror-induced anapole mode. Homoharringtonine price Electric anapole mode and its magnetic counterpart are, respectively, investigated in two types of MDM configurations according to their own symmetric characteristics. Benefiting from the double PEC mirror effects, the doubly mirror-induced electric and magnetic anapole modes possess the larger average electric-field enhancement factors (9 and 56.9 folds compared with those of the conventional ones, respectively), as well as the narrower line widths. This work will pave a new way for tailoring and boosting anapole modes in metal-dielectric hybrid nanoresonators and open up new opportunities for many significant applications in nonlinear and quantum nanophotonics.This Letter analyzes photoconductive (PC) terahertz (THz) emitters based on the semi-insulating (SI) forms of GaAs and InP. The dependencies of the emitters are studied under the extremes of the bias field and pump fluence to reveal the underlying physics of charge carrier photoexcitation, transport, and emission. The bias field dependence shows that SI-GaAs PC THz emitters are preferentially subject to space-charge-limited current, under the influence of trap states, while SI-InP PC THz emitters are preferentially subject to sustained current, due to a prolonged charge carrier lifetime and the ensuing joule heating. The pump fluence dependence shows space-charge and near-field screening for all emitters, with SI-GaAs predisposed to near-field screening (under the influence of transient mobility) and SI-InP predisposed to space-charge screening. Such findings can support a deeper understanding of the underlying physics and optimal performance of SI-GaAs and SI-InP PC THz emitters.Hexagonal boron nitride (hBN) is a layered dielectric material with a wide range of applications in optics and photonics. In this work, we demonstrate a fabrication method for few-layer hBN flakes with areas up to 5000µm2. We show that hBN in this form can be integrated with photonic microstructures as an example, we use a circular Bragg grating (CBG). The layer quality of the exfoliated hBN flake on and off a CBG is confirmed by Raman spectroscopy and second-harmonic generation (SHG) microscopy. We show that the SHG signal is uniform across the hBN sample outside the CBG and is amplified in the center of the CBG.The ultrafast detection of single photons is currently restricted by the limited time resolution (a few picoseconds) of the available single-photon detectors. Optical gates offer a faster time resolution, but so far they have been applied mostly to ensembles of emitters. Here, we demonstrate through a semi-analytical model that the ultrafast time-resolved detection of single quantum emitters can be possible using an optical Kerr shutter at gigahertz rates under focused illumination. This technique provides sub-picosecond time resolution, while keeping a gate efficiency at around 85%. These findings lay the ground for future experimental investigations on the ultrafast dynamics of single quantum emitters, with implications for quantum nanophotonics and molecular physics.Population of the chemically active singlet 1Δg(0) state of molecular oxygen occurring due to direct laser excitation of the 1Δg(1)←3Σg-(0) transition has been observed for the first time, to the best of our knowledge, in oxygen molecules dissolved in organic solvents saturated with air under natural conditions (room temperature and normal atmospheric pressure). The data were obtained in 1 cm spectrophotometric cells due to the application of a set of high-power IR fiber and diode lasers. The rate of laser generation of the singlet (1Δg(0)) states in oxygen molecules was monitored by a chemical trapping method. It was found that the action spectra of singlet oxygen generation have one distinct band with a maximum at 1070 nm and half-width of ∼10nm. The absorption coefficients at 1070 nm were shown to be 100-110-fold lower than those at the main oxygen absorption peak (1273 nm) corresponding to the 1Δg(0)←3Σg-(0) transition. Under excitation at 810-1061 nm, very low trapping rates were observed, which did not depend on excitation wavelengths being probably caused by thermal effects. There was no reliable increase in the trapping rate under irradiation at 810 and 920 nm corresponding to the 1Δg(2,3)←3Σg-(0) transitions. This fact suggests that absorbance corresponding to these transitions is much lower than that at 1070 nm. The obtained results are important for both spectroscopy of oxygen and mechanistic studies of biological and therapeutic action of laser radiation.In this Letter, a distributed acoustic sensor (DAS) with a sensing range in excess of 150 km is reported. This extended sensing range is achieved by adding a low-loss enhanced-backscattering fiber at the far end of a standard single-mode fiber. A conventional DAS system along with inline optical amplifiers are used to interrogate the sensing fiber. The combined system exhibits a minimum detectable strain of 40 nε at 1 Hz over a spatial resolution of 5 m.
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