Photonics and Nanostructures-Fundamentals and Applications最新文献

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.

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.

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).

In this study, we introduce a metamaterial absorber operating in the near infrared region. The current metamaterial absorber (MMA) comprising Silver-SiC-Gold demonstrates an absorptivity exceeding 80% within the wavelength range of 770 nm to 1150 nm. The current metamaterials absorber exhibits independence from both polarization and incident angle. Additionally, we made comparison between the proposed Metal-Insulator-Metal (MIM) based MMA with other previously reported MMA using Silicon Carbide (SiC) and another dielectric spacer layer.

Detection of extreme temperatures plays a key role in metallurgy, aerospace, nuclear industries, and even astronomy. Herein, materials and optical technologies capable of detecting the temperatures above 3000 K are still in their infancy. Here, we report on a detection of 3800 to 4500 K through the emission of a blackbody, for which the metal-organic frameworks (MOFs) are used. The rapid heating of MOFs by laser radiation leads to the threshold blackbody emission (centered from 650 to 750 nm), the corresponding temperature of which is directly related to the structure of MOF. The results on such structure-related temperatures of the blackbody emission of MOFs, thereby, expand their use in photonics and sensing in general.

Using the previously introduced modified discrete dipole approximation (DDA) method by applying the full details of the nanoparticle and its surrounding environment, the detection sensitivity of molecules by plasmonic Rod-based nanosensors, including U-shaped and Rod-shaped structures, was investigated. In the calculations, the two factors of the magnitude of the wavelength shift and the ability to distinguish molecules with similar properties were of significant interest. The results indicated that the sensitivity of Rod-based nanostructures is significantly higher than that of spherical nanoparticles. Among the plasmonic Rod-based nanosensors, the silver U-shaped structure performs better than others. The wavelength shift of the absorption spectrum of different nanosensors for a given molecule was very different, making it possible to detect very similar molecules from each other by testing different sensors.

Mid-infrared spectroscopy enabled by silicon photonics has received great interest in recent years as a pathway for a scalable sensing technology. The development of such devices would realise inexpensive and accessible instrumentation for a wide variety of uses over numerous fields. However, not every sensing application is the same; to produce sensors for real-world scenarios, engineers need flexibility in device design but also need to maintain compatibility with scalable fabrication processes. Sub-wavelength gratings can offer a solution to this problem, as they enable the engineering of optical properties using standard fabrication techniques and without requiring new materials. By using sub-wavelength gratings, specific design approaches can be tailored to different applications, such as increasing the interaction of a sensor with an analyte or broadening the bandwidth of an integrated photonic device. Here, we review the development of sub-wavelength grating-based devices for mid-infrared silicon photonics and discuss how they can be exploited for spectroscopic and sensing devices.