Photonics and Nanostructures-Fundamentals and Applications最新文献

This paper presents systematic design and analysis of a dual-purpose integrated processor based on graphene hybrid plasmonic concentric add-drop microring resonators for fast differentiation and integration. The footprint of this processor is equal to 4 × 4.358 μm², containing two concentric rings with small radii of 1679 and 1204 nm. Performance of the designed dual-purpose processor for the first and fractional-orders differentiation and integration has been analyzed by the three-dimensional finite-difference time-domain method in the frequency and time domains and the accuracy of the results has been confirmed using the formulas of the ideal math differentiator and integrator. From the point of view of the performance specifications, the designed dual-purpose temporal processor has excellent 3 dB bandwidth, insertion loss, energy efficiency, and accuracy in the first and fractional-orders differentiation and integration.

We have developed a theory of the Bragg scattering for metallic nanohybrid made of an ensemble of metallic nanorods doped in a substrate. The substrate can gas, liquid or solid. An external laser field is applied to study the Bragg scattered light. The photons from the incident laser interact with the surface plasmons od nanorods and produce surface plasmon polaritons (SPPs). The incident laser field also induced dipoles in the ensemble of nanorods and they interact with each other via the dipole-dipole interaction (DDI). We have developed a theory for Bragg scattering for metallic nanohybrids using the coupled-mode formulism based on Maxwell’s equation in the presence of SPP and DDI fields. It is found that the theory of Bragg scattered depends on the susceptibility induced by the SPP and DDI fields. We used the quantum mechanical density matrix method to calculate the susceptibility. An analytical expression of the Bragg scattered light intensity is obtained. These expressions can be useful for experimental scientists and engineers who can used them to compare their experiments and make new types of plasmonic devices. Next, we have compared our theory with the experiment data for a nanohybrid made of ensemble of Au-nanoris doped in water. We found a good agreement between theory and experiments. We have also performed the numerical simulations to study the effect of SPP and DDI fields on the Bragg intensity. We have predicted an enhancement the Brag intensity due to the SPP and DDI couplings. The enhancement is due to the two extra scattering mechanisms of the SPP and DDI polaritons with acoustic phonons. We have also found that the one peak in the Bragg intensity can be split int many peaks due the SPP coupling, DDI coupling and phase factor. The splitting is due the Bragg factor appearing in the theory, and it includes the coupling of the incident laser, SPP and DDI electric fields with of acoustic phonons. The enhancement effect can be used to fabricate new types of nanosensors. Similarity, splitting phenomenon can be used to fabricate new types nanoswitches where one peak can be considered as the OFF position and many peaks can be considered as the ON position.

Silicon photonics is widely used for near InfraRed (IR) applications up to 1.6 µm. It plays a key role in short-range optical data communications. However, silicon photonics does not really address mid-IR applications, particularly in the 1.6–5 µm wavelength range. This spectral region is essential for environmental/life sensing and safety applications relying on the optical features of molecular vibrations, the aim being to discern and categorize complex chemical entities. Growing markets for such analysis prioritise sensitivity, specificity, compactness, energy-efficient operation and cost effectiveness. The need for a CMOS-compatible integrated photonic platform for the mid-IR is obvious. Such fully-group-IV semiconductor platform should include low-loss guided interconnects, detectors, modulators and, critically, efficient integrated light sources. This paper provides a comprehensive review of recent advances in GeSn-based mid-IR silicon-compatible devices, including optically and electrically pumped lasers, light-emitting diodes and photodetectors. It also discusses the principles underlying these developments, with focuses on material growth techniques and processing methods.

In this paper, we analyse a novel photonic sensor utilising mode-transition in hexagonal photonic crystal fiber (HPCF) to monitor the ethanol content in an ethanol-gasoline blend. Using the finite-element method, the mode-transition from LP₀₂ cladding-mode to LP₀₁ core-mode is accomplished by raising the refractive index (RI) of the analyte layer, which removes the necessity of an additional high RI layer deposition at the fiber surface. We have rigorously optimized the air-filling fraction of the HPCF cladding such that the analyte RI range for the mode-transition would correspond to 0–25% v/v of ethanol in the blend, which is within its commercial range of ethanol-gasoline blend. With increasing analyte RI, we have observed the occurrence of a minimum in the total modal power carried by the sensor. We determine the sensitivity through this modal power variation by dividing it (about the power minimum) into two RI dynamic ranges of 1.400–1.410 (i.e., 25–11% ethanol) and 1.410–1.418 (i.e., 11–0% ethanol), respectively. The maximum calculated sensitivity of the sensor within the linear regime of the modal power variation is 0.46 dBm/% v/v and 0.40 dBm/% v/v, respectively, which are twice as high as the sensitivity offered by the FBG and LPG based sensors over the same dynamical range. In addition to the high sensitivity, the proposed sensor does not require any high-RI layer coating, making its design simpler and easier to implement.

This paper presents a terahertz beam splitter based on an "I" type double open ring structure. Its structure unit is a typical metal-medium-metal structure; the top metal pattern comprises an "I" type double open ring, and the bottom layer is a continuous metal plate. The phase gradient metasurface of 8 × 8 is formed by changing the opening size and radius of the I-shaped double-open ring. When a y-polarized wave is an incident vertically along the -z-axis and the +z axis, respectively, the y-polarized waves will be divided into four beams with different energy distributions along the x and y-axis, and two different beam splitting ratios can be obtained from the two incident modes. In 0.7 THz, when the y polarized waves are incident vertically along the -z-axis and +z axis, the beam splitting ratio is 0.8 and 2.1, respectively, and the beam splitting ratio is tuned. This terahertz beam splitter has the advantages of small size and low cost and can be used in terahertz communication, terahertz imaging, terahertz stealth, and other fields.

Crystalline and morphological defects in the perovskite film affect the operation of light-emitting devices. Thus, advanced and scalable fabrication techniques can improve device properties. In this work, we use slot-die coating at ambient conditions, followed by hot air drying, to produce CsPbBr₃ light-emitting electrochemical cells. We compare this method to spin-coating and analyze film morphology and optical properties. We reveal that annealing the film on a hot plate increases PLQY and Shockley-Read-Hole lifetime, but worsens film morphology. In contrast, hot air drying during deposition improves morphology but reduces photoluminescence. The slot-die coating shows better results for device fabrication. With InGa and Al top electrodes, we achieve luminance 8100 cd m⁻² and 2900 cd m⁻² at a 5 V bias, respectively.

Tamm plasmon modes are used to realize the modulation of multi-photon processes. Through effectively combining the rear-earth doped layer and a monolayer graphene in a Tamm structure, the emission of multi-photon processes can be tuned by the applied voltage. Results show that the proposed structure has a narrow absorption peak near 1550 nm, which is corresponding to the excitation source wavelength of the multi-photon processes. Importantly, the emission intensity of multi-photon processes can be tuned from 1 fold to ∼10.1 fold when we changed the applied voltage. Meanwhile, the emission color of the multi-photon processes can be tuned from yellow to green via adjusting the applied voltage. The proposed voltage tuning approach may be promoted to all kinds of nonlinear optical phenomenons, like Stimulated Raman Scattering, optical mixing and photorefractive effect.

Plasmonics is gaining prominence in the area of optical sensing due to the unique way that noble metals and light interact to produce subwavelength confinement. A Metal Insulator Metal waveguide based plasmonic nanosensor exhibiting multi Fano resonance is proposed. The characteristics of transmittance of the proposed sensor are investigated using the Finite Difference Time Domain methodology. Three Fano resonances can be seen in the transmission characteristic with different sensitivities of 992.4 nm/RIU, 1294.8 nm/RIU and 2065.5 nm/RIU at 1.0257 μm, 1.3239 μm and 2.0798 μm respectively. Furthermore, the sensor performance is investigated for potential fabrication issues arising out of variation in structural parameters such as the coupling distance and the radius (both inner and outer) of the semi-ring arc resonator. The performance of the sensor is also assessed for performance metrics like the Figure of Merit (FOM), Q factor, and Detection Limit, which are obtained as 39.7 RIU⁻¹, 39.9 and 0.025 respectively. The characteristics of the Fano resonances obtained through simulation is also validated by matching it with the theoretical Fano line shape function. The proposed sensor can find its use in biosensing applications.

The analysis of gases by THz radiation offers a high degree of discrimination due to the narrow linewidths that are observed at low pressure. The sensitivity of existing high-resolution instruments is limited by the availability and performance of critical system components. This study uses two key components with physical structures at the wavelength scale to realise a high finesse THz cavity. The cavity is characterised and incorporated into a spectrometer. Sensitivity limits of the instrument are experimentally demonstrated for trace and pure gases. Both CEAS (Cavity Enhanced Absorption Spectroscopy) and CRDS (Cavity Ring-Down Spectroscopy) configurations are shown to give sub-ppm detection levels. The cavity has also been used to measure the atmospheric losses.

In this study, we developed a novel method based on uniform and graded gratings on the front surface of ultra-thin film Si solar cells to enhance light absorption. The proposed gratings were designed in two configurations comprising penetration into the active layer and placement on it. These structures enhance absorption by scattering and diffracting light, and enlarging the optical path for photons. Simulations based on the finite element method and finite difference time domain technique showed that the graded gratings could significantly enhance absorption in the visible and infrared regions. The maximum current density and efficiency achieved for graded gratings placed on the top surface of the active layer were 21.7 mA/cm² and 23.9%, respectively (47.6% and 48.4% higher compared with the reference cell).