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All-dielectric nanostructures have attracted attention for highly efficient light manipulation. Higher Q-factor Fano resonance can be excited due to the rich phenomenology of optical modes supported by high-index dielectric materials with low intrinsic material loss, including both electric and magnetic multipolar Mie resonances. So far, there have been few studies done on the sensing with Fano-resonant all-dielectric resonator nanostructures. Here, an all-dielectric self-referenced optical sensor is numerically demonstrated based on Si quadrumers and mirror-symmetric 1-D photonic crystals (1DPCs) hybridstructure, operating at the infrared wavelength range with higher sensing performance and much more stable reference signal. Magnetic Fano resonance and Fabry-Perot resonance were combined into such a hybridstructure for the first time. The influences of the gap distance, including Δx and Δy, on the coupling effects between the Si nanodimers along the polarization direction and the 1DPCs are systematically discussed. The sensing performance has been numerically investigated in different analytes with the sensitivity and figure of merit (FOM) of 760 nm/RIU and 1515 RIU−1 respectively, which paves the way to be a much more sensitive detection of small refractive index changes in an unstable environment and suggests potential applications in biological and chemical sensing. [ABSTRACT FROM AUTHOR]

It is well known that higher diffraction order suggests a stronger dispersion for gratings with the same period. Here, a broadband high-efficiency three-layer all-dielectric rectangular-groove transmission grating operating at the −2nd order is designed under second Bragg incidence. An initial solution of the grating parameters is obtained quickly by using the simplified modal method (SMM). Moreover, a clear explanation for the physical mechanism behind high efficiency and wide bandwidth is also given through this method. After that, a more accurate solution of the grating structure is optimized in further based on rigorous coupled wave analysis and simulated annealing algorithm. The simulation results indicated that a wavelength bandwidth from $1.454~\mu \text{m}$ to $1.531~\mu \text{m}$ and an angle bandwidth from 37.32° to 43.3° could be achieved for efficiency over 95% under second Bragg incidence at the wavelength of $1.5~\mu \text{m}$ for TE polarization. It is the first time using SMM to predict the broadband characteristic of multilayer-gratings under second Bragg incidence. [ABSTRACT FROM AUTHOR]

We present a type of generalized circular Dammann gratings (GCDGs) with controllable impulse ring profiles. Different from impulse rings generated by traditional circular Dammann gratings, the intensity profile of impulse rings can be tuned by redesigning the phase structure of GCDGs. Also, the physical picture behind this controllable impulse ring profile is given clearly. As examples, four one-order binary (0, $\pi $ ) GCDGs are designed and fabricated for generation of impulse rings with four different intensity profiles. In addition, GCDGs with continuous-phase profile are also demonstrated for generation of multiple concentric equal-intensity impulse rings with different intensity profiles. This type of impulse rings with tunable intensity profiles will enrich the function of CDGs, and it should be of high interest for its potential applications in various realms, such as structured pumping laser, novel optical manipulation, generation of dark perfect vortices, and optical testing and measurement. [ABSTRACT FROM AUTHOR]

3-D profilometry is one of the most important branches of measurement science and technology. In this paper, a new colorful 3-D imaging method using near-infrared (NIR) laser (850 nm) dot array generated by a Dammann grating is proposed. Two NIR cameras mounted with narrowband passed filters are adopted to capture laser patterns on objects. A color camera mounted with an infrared cutoff filter is adopted to capture color information. A simplified multiviews’ matching method for dot array, which is the key of this 3-D imaging system, is proposed. A new geometric constraint named ray constraint is applied to multiview matching with the help of precalibration of laser dot array. Point clouds with color information are obtained according to triangulation. We used the experimental apparatus to scan a colorful plane with colorful attachments on it, and its colorful point clouds (about 56 000 sample points) were obtained. Experiments demonstrate that this apparatus achieves a depth accuracy of 0.21 mm at the measuring distance of 300 mm. This new colorful 3-D imaging has advantages of low cost, low power consumption, flexible structure, and portability, which should be highly interesting for practical applications. [ABSTRACT FROM PUBLISHER]

We proposed and demonstrated an efficient vortex Nd:YVO4 laser under the utilization of a circle Dammann grating (CDG). As a simple binary-phase component, CDG was inserted into the pump unit of this laser-diode end-pumped solid-state laser and reshaped the pump radiation into annular profile with high efficiency. Moreover, such utilization of CDG avoided additional modification to laser cavity. As a result, the laser emitted vortex beam with a high slope efficiency of 51% and a maximum beam power of 554 mW at 1.75-W incident pump power. [ABSTRACT FROM PUBLISHER]