Photonics and Nanostructures-Fundamentals and Applications最新文献

Due to its diverse crystal configurations with varying bandgaps, Silicon Carbide (SiC) has been widely utilized by numerous researchers in the preparation of photodetectors. In this paper, we propose high performance tunable photodetector with graphene-based SiC grating structure. The photodetector can achieve perfect absorption and the responsivity of 10.61 A/W at 11.7 μm wavelength. The tunable broadband photodetection from 11.4 μm to 12 μm can be obtained by adjust graphene’s Fermi level. Compared with existing graphene-based photodetector with or without SiC structures, our structure has more flexible detection and higher performance. In addition, we explain the standing wave phenomenon observed during the tuning of the photodetector structure. This provides a new direction for the development of high-quality infrared photodetectors.

In this paper, a D-shaped photonic crystal fiber (PCF) sensor based on a Sagnac interferometer is proposed, and it can achieve ultrahigh refractive index (RI) and temperature sensitivity when operating around the turning point of group birefringence (B_g). We undertake a theoretical analysis on B_g and a simulation calculation to study the sensing characteristics and obtain the optimized structure parameters of the D-shaped PCF sensor. The simulation results show that the maximum average RI sensitivities can reach 3253.33 and 15500 nm/RIU in the RI range of 1.33 to 1.35 and 1.40 to 1.42, respectively. When the temperature changes from -50 to 0 °C and 0 to 50 °C, the maximum average temperature sensitivities are up to 10.11 and 10.67 nm/°C, respectively. The proposed D-shaped PCF sensor can achieve dual-parameter sensing and has great potential for practical applications in biochemical and environmental science.

This letter presents a terahertz angle sensor using a rectangular and double L-shaped structure. The structure unit of the sensor consists of a typical metal-medium structure, with the top metal pattern comprising a rectangle and a double L-shaped structure. At the same time, the bottom layer is made of polyimide, a dielectric material. By varying the position and number of L-shaped structures, a terahertz angle sensor based on a spring-shaped structure is created. The terahertz angle sensor achieves a Q value of 120.6 with a sensitivity of 3.45 GHz per degree. The terahertz angle sensor offers high-angle resolution and may find applications in terahertz communication, imaging, sensing, and other related fields.

In this work, Surface-enhanced Raman spectroscopy (SERS) along with machine learning algorithms (MLA) were used to detect and classify the viral particles to assess the possibility of using the spectra of inactivated influenza A viruses for MLA training and spectra database compilation for further study and diagnosis of intact forms of the virus. Viral particles inactivation was performed by formalin, ultraviolet and beta-propiolactone. Support vector method and principal component analysis allowed to classify intact and inactivated viral particles spectra with an accuracy of 80.0–96.7 %. The results obtained suggest that it is not advisable to create a spectral database and train machine learning algorithms for their further application in SERS diagnostics of intact viruses based on the spectra of the inactivated virus particles.

Based on the local resonance effect of elastic waves, three single-phase acoustic metamaterials are proposed in this paper. Based on the finite element method and Bloch's theorem, the energy band structure diagrams and vibration modes are plotted, and the band gap properties and band gap opening mechanism of these structures are explored. New structures possessing lower frequency band gaps are obtained by topological optimization. The transmission curves verify the accuracy of the band gap and the vibration attenuation ability of the structure. Finally, the structural parameters were adjusted and the effect of each parameter change on the band gap characteristics was analyzed. The results show that the proposed structure has a maximum band gap coverage of 72.4 % and a strongest attenuation peak of less than −400 (dB) due to the occurrence of a local resonance. This paper provides a methodology for analyzing the vibration and noise reduction performance of single-phase material phononic crystals, as well as a three-dimensional phononic crystal with potential for practical applications.

In this paper, a 1×4 ultra-compact wavelength division multiplexing cascaded device(DMC) with an arbitrary splitting ratio based on adjoint topology optimization reverse design is proposed, which is approximately two orders of magnitude smaller than that of conventional waveguide devices. It can simultaneously perform wavelength demultiplexing, mode conversion, and arbitrary ratio power splitting. The DMC separates 1310 nm and 1550 nm wavelengths, converts the input light from fundamental transverse mode (TE0) to first-order transverse mode (TE1) and second-order transverse modes (TE2), and performs arbitrarily proportional power splitting of the converted higher-order light source.

We theoretically studied the linear, third-order nonlinear and total optical absorption coefficient changes of a typical GaAs/Al_0.3Ga_0.7As quantum dot system under the influence of hydrostatic pressure and temperature. The influence of hydrostatic pressure and temperature on the system is treated within the framework of effective mass. In this method, the relative changes of linear and nonlinear absorption coefficients are obtained by using density matrix method and iterative method. In addition, we also reveal the mechanism of the influence of hydrostatic pressure and temperature on the nonlinear optical properties, which is of great significance for us to better understand the causes. We have shown that hydrostatic pressure and temperature change the effective mass, resulting in significant changes in the linear and nonlinear optical properties of the system. In addition, we also reveal the mechanism of the influence of effective mass on the nonlinear optical properties, which is of great significance for us to better understand the causes.

In spectroscopy, having access to a wide range of wavelengths within the mid-infrared region is crucial for conducting thorough and versatile analyses. In our research, we successfully demonstrate numerically the generation of supercontinuum within a waveguide made of silicon nitride loaded onto lithium niobate on a sapphire substrate, with a specific focus on the mid-infrared wavelength range. By implementing effective lateral leakage and dispersion engineering techniques, we have significantly broadened our system’s spectral range, covering wavelengths from the near-infrared (near-IR) to the mid-infrared (mid-IR) regions. Our results indicate that when a silicon nitride-loaded lithium niobate waveguide is excited with a commercially available femtosecond fiber laser pump at 2070 nm, it has the capability to produce a supercontinuum that spans more than one octave within the mid-infrared wavelength range.

Compact and efficient devices for radiation beam manipulation are in increasing demand by terahertz technologies. Herein, we introduce an ultrathin metal-polymer photolithographic metagrating operating as a transmissive beam splitter with a wide refraction angle of 58^∘ at sub-THz frequencies. Harnessing this recently proposed complex media platform, composed of sparse periodic arrays of meta-atoms, constraints of conventional metasurfaces with densely packed unit cells can be alleviated. The devised splitter, synthesized semianalytically and demonstrated experimentally, features deeply subwavelength thickness due to the unique manufacturing process employed, serving as a promising alternative to thick waveguide-based metagratings previously reported for this frequency range.

The detectable range and sensitivity play a key role in the accuracy and range of applications available for lab-on-a-chip sensing systems. Here, we propose and numerically demonstrate an on-chip refractive index sensor simultaneously possessing wide detectable range and high sensitivity through monitoring the two-peak envelope spectrum of a subwavelength grating microring resonator. The principle lies in the combination of the envelope spectrum tracking scheme and the light field releasing in subwavelength grating waveguides. The structure of the subwavelength grating microring resonator is designed to adjust the wavelength dependence of its critical coupling condition, so that the two-peak envelope spectrum can be formed and centered at critically coupled wavelengths. By probing the drift of the two-peak envelope spectrum within the C+L band (1530–1625 nm), we lift the free spectral range constraint on the detectable range and broaden it up to 0.46 RIU. Meanwhile, a sensitivity of 444 nm/RIU is achieved. This investigation provides an attractive candidate for high performance integrated sensors, and thus may pave the way for lab-on-chip sensing, especially in application scenarios demanding both wide detectable range and high sensitivity.