Jiaqi Yang

Bio: Jiaqi Yang is an academic researcher from Beijing Institute of Technology. The author has contributed to research in topics: Dielectric & Materials science. The author has an hindex of 3, co-authored 4 publications receiving 102 citations.

High sensitivity of taper-based Mach–Zehnder interferometer embedded in a thinned optical fiber for refractive index sensing

Abstract: A taper-based Mach–Zehnder interferometer (MZI) embedded in a thinned optical fiber is demonstrated as a highly sensitive refractive index (RI) sensor. A RI sensitivity of 2210.84 nm/RIU (refractive index unit) is obtained at the external RI of 1.40, which is ten times higher than that of normal taper- and long-period fiber grating (LPFG)-based sensors. The sensitivity can be further improved by decreasing the diameter of the thinned fiber and increasing the interferometer length of the MZI. The proposed MZIs have lower temperature sensitivities compared with normal fiber sensors, which is a desirable merit for RI sensors to reduce the cross sensitivity caused by thermal drift.

Broadband near-infrared TiO2 dielectric metamaterial absorbers.

Abstract: Metamaterial absorbers (MAs) have drawn increasing attention due to their prospects in many fields such as sensing, thermal emission, solar energy harvesting, etc. However, it remains challenging to realize broadband MAs with a simple structure. Here, we propose a broadband, polarization-insensitive, and omnidirectional MA working in the near-infrared range with simple structure, which is composed of titanium dioxide (TiO2) cylinder nano-antenna arrays on the top of a vanadium (V) film deposited on a silicon substrate. This device demonstrates broadband absorption spectra from 820 to 1440 nm with the absorption above 90%, with high absorption up to the incident angle of ∼50°. The broadband absorption of the designed MA is mainly attributed to the interaction both of dielectric cavity resonance and electric dipole resonance. The electric and magnetic field intensity distribution of the MA are analyzed to better understand its absorption mechanism. In addition, the effects of the geometrical parameters on absorption are discussed. The demonstrated MA is relatively easy to fabricate and can be realized with other proper materials to work in other wavelength bands. The design is useful for applications such as solar energy harvesting, sensing, and camouflage.

High-efficiency, broadband, and wide-angle all-dielectric quarter wave plate based on anisotropic electric and magnetic dipole resonances

Abstract: Metadevices based on dielectric nanostructure with excitation of electric and magnetic resonances have shown high efficiency for polarization control compared with conventional manipulation methods, as well as plasmonic structure metadevices. Since both the electric and magnetic dipole (MD) resonances can be precisely adjusted by optimizing geometric parameters of the resonators to meet the desired wavelength, this paper proposes an approach to implement the high transmittance metadevices operating at preferred wavelengths. By employing this method, we demonstrate an all-dielectric quarter wave plate (QWP) metasurface with high transmittance (>85%) and high polarization conversion efficiency (>0.88) in a broad telecom waveband. At the same time, conversion efficiency is nearly unaffected for incident angles within 75°. With features of high transmittance, wide angle, and invertible linear to circular polarization conversion, the all dielectric QWP can be a good replacement for plasmonic metasurface devices and offers a further step in developing polarization and phase manipulation metadevices.

Optical characterization of DNA origami-shaped silver nanoparticles created through biotemplated lithography.

Abstract: Here, we study optically resonant substrates fabricated using the previously reported BLIN (biotemplated lithography of inorganic nanostructures) technique with single triangle and bowtie DNA origami as templates. We present the first optical characterization of BLIN-fabricated origami-shaped silver nanoparticle patterns on glass surfaces, comprising optical transmission measurements and surface-enhanced Raman spectroscopy. The formed nanoparticle patterns are examined by optical transmission measurements and used for surface enhanced Raman spectroscopy (SERS) of Rhodamine 6G (R6G) dye molecules. Polarization-resolved simulations reveal that the higher SERS enhancement observed for the bowties is primarily due to spectral overlap of the optical resonances with the Raman transitions of R6G. The results manifest the applicability of the BLIN method and substantiate its potential in parallel and high-throughput substrate manufacturing with engineered optical properties. While the results demonstrate the crucial role of the formed nanogaps for SERS, the DNA origami may enable even more complex nanopatterns for various optical applications.

Visible light waveband Dammann grating based on all-dielectric metasurface.

Abstract: Dammann gratings (DGs) can generate a spot array in a particular arrangement. In recent years, DGs have been used in many fields such as laser beam splitting and optical coupling. Nanograting encoding technology can achieve a high signal-to-noise ratio and high-efficiency diffraction distribution; it also provides new design ideas for realizing the miniaturization and deviceization of DGs. In this work, we have comprehensively studied the DG based on an all-dielectric metasurface, which can produce a 5×5 diffraction spot array with a diffraction angle of 20∘×20∘. In an operation waveband from 650 to 690 nm, the DG has superior performance with high efficiency ≥60%; meanwhile, it achieves a relative low contrast ratio ≤0.33. Owing to high efficiency, wide waveband performance, and polarization insensitive property, the all-dielectric metasurface DG can provide possibilities for various application, including laser technology and optical information processing.

Sensitivity characteristics of long-period fiber gratings

Abstract: Full characterization of the sensitivity of the LPFG is a precursor to practical device design, and knowledge of the sensitivity of the Long-period fiber gratings to the parameters of its physical environment processed is clearly important. We present a theoretical and experimental investigation into the sensitivity of long-period fiber gratings as a function of processed parameters by high-frequency CO 2 laser pulses.

High sensitivity and high Q-factor nanoslotted parallel quadrabeam photonic crystal cavity for real-time and label-free sensing

Abstract: We experimentally demonstrate a label-free sensor based on nanoslotted parallel quadrabeam photonic crystal cavity (NPQC). The NPQC possesses both high sensitivity and high Q-factor. We achieved sensitivity (S) of 451 nm/refractive index unit and Q-factor >7000 in water at telecom wavelength range, featuring a sensor figure of merit >2000, an order of magnitude improvement over the previous photonic crystal sensors. In addition, we measured the streptavidin-biotin binding affinity and detected 10 ag/mL concentrated streptavidin in the phosphate buffered saline solution.

A Review of Microfiber and Nanofiber Based Optical Sensors

Abstract: Rapid advances in optical microfiber and nanofibers (MNF) based sensors have been driven by powerful industries such as automotive, biomedical and defense, with the increasing demand for highly-sensitive, selective, nonintrusive, fast-response, compact and robust sensors that can perform in-situ measurements at remote and harsh environments. A diverse range of MNF based sensors have been developed for measuring refractive index, bio-chemical, temperature, current, displacement, bend, surface, acceleration, force, rotation, acoustic, electric field and magnetic field. Given the growing interest for this exciting area of scientific research, new designs are emerging continuously at a fast pace. This paper attempts to provide a comprehensive review of all MNF based sensors reported to-date. Sensors are divided according to their morphology and measurand.

High-Q and high-sensitivity width-modulated photonic crystal single nanobeam air-mode cavity for refractive index sensing

Abstract: We propose a novel optical sensor based on a one-dimensional (1D) photonic crystal (PhC) single nanobeam air-mode cavity (SNAC). The performance of the device is investigated theoretically. By introducing a quadratically modulated width tapering structure, a waveguide-coupled 1D-PhC SNAC with a calculated high quality factor of 5.16×10(6) and an effective mode volume of V(eff)∼2.18(λ/n(si))(3) can be achieved. For the air mode mentioned above, the light field can be strongly localized inside the air region (low index) and overlaps sufficiently with the analytes. Thus, the suggested PhC SNAC can be used for high-sensitivity refractive index sensing with an estimated high sensitivity of 537.8 nm/RIU. To the best of our knowledge, this is the first PhC single nanobeam geometry that features both high Q-factors and high sensitivity, and is potentially an ideal platform for realizing ultracompact lab-on-a-chip applications with dense arrays of functionalized spots for multiplexed sensing.

S-Tapered Fiber Sensors for Highly Sensitive Measurement of Refractive Index and Axial Strain

Abstract: An S-tapered fiber sensor has been realized on the common single-mode fiber by a fusion splicer. The S fiber taper (SFT) can be considered as a compact fiber Mach-Zehnder interferometer with the total length of hundreds of microns. The spectral characteristics of the SFTs with different structure parameters including axial offsets and taper waist diameters have been studied. Sensing experiments have also been carried out to test their response to refractive index (RI) and axial strain. The SFT with an axial offset of 114 μm and a taper waist diameter of 54.6 μm exhibits the best combination property. Its RI sensitivity reaches as high as 2066 nm/RI unit in the RI range of 1.407-1.421 and the average strain sensitivity is -183.4 pm/μe, which is the highest strain sensitivity, to the best of our knowledge, with one or two orders of magnitude larger than the existing fiber strain sensors.