Optical and Quantum Electronics最新文献

Compact mode order converters (MOCs) operating at the mid-infrared regime are reported using silicon-on-calcium fluoride platform. The suggested designs convert the fundamental transverse electric (TE) mode to first and second order TE modes with total device lengths of only 5.89 μm and 5 μm, respectively, at λ = 3.14 µm. The full vectorial 3D finite-deference time-domain is utilized to analyze the TE₀ → TE₁ and TE₀→TE₂ MOCs. The proposed designs depend on using dielectric material of Si₃N₄ inside the Si core region to improve and facilitate the mode conversion process. The conversion efficiencies (inter-modal crosstalks [CTs]) are equal to 93.4% (− 19.2 dB), and 90% (− 17 dB) for TE₀: TE₁ and TE₀:TE₂ MOCs, respectively. Moreover, the reported designs have a wide wavelength range of 300 nm, where the conversion-efficiency (CE) and maximum CT are > 86% and <  − 14.3 dB, respectively. Further, the fabrication tolerance of the suggested structures is handled to guarantee the presented mode converter’s fabrication viability. The reported designs can also be extended to other wavelength bands. In this regard, our device’s numerical results at λ = 1.55 µm are reported and compared to other conventional MOCs. The conversion efficiencies (inter-modal crosstalks [CTs]) are equal to 90% (− 19 dB), and 88% (− 19.7 dB) for TE₀: TE₁ and TE₀: TE₂ MOCs, respectively, at λ = 1.55 µm.

Microwave photonic filters (MPF) are among the most crucial components required for meeting the demands of high-speed and high-frequency signal processing of modern telecommunication systems. For the first time, here, we propose an MPF based on a double wavelength spacing Brillouin-Raman fiber laser (BRFL) to realize a versatile bandpass filter. The proposed setup generated 100 optical taps output with ~ 20 GHz spacings as the light source of the MPF. A dispersive medium of 5 km long single mode fiber and 3.46 km long dispersion compensating fiber were used to characterize the effect of the time delay on the central frequency of the MPF passband. A reconfigurable 3-dB bandwidth from 150 MHz to 1.12 GHz centered around 10.3 GHz is achievable by varying the BRFL optical channel numbers using 10 to 100 optical taps with 20 GHz spacing. The 3-dB bandwidth and Q-factor of the proposed MPF were investigated experimentally and found to be in good agreement with simulation, demonstrating the potential of the BRFL as a laser source for the realization of flexible and versatile radio frequency transversal filters with potentially reduced cost and complexity.

This study includes the synthesis and characterization of N-GQDs, pure TiO₂, and TiO₂/N-GQDs nanocomposites thin films prepared by spin-coating technique. The gel of TiO₂ nanoparticles and N-GQDs was prepared using sol–gel and hydrothermal techniques, respectively. Further, the TiO₂/N-GQDs nanocomposites were prepared by sol–gel method in the weight % ratio of 90 TiO₂/10 N-GQDs and 80 TiO₂/20 N-GQDs. The structural, optical and electrical behaviour of these thin film has been investigated using XRD, AFM, HR-TEM, UV–Visible spectroscopy and two probe methods. The XRD study had confirmed the tetragonal structure of TiO₂. The average crystallite size calculated using Debye–Scherrer’s equation has been found to be 13.56 nm for TiO₂ which decreases up to 11.31 nm for 80 TiO₂/20 N-GQDs. The HR-TEM analysis had confirmed the successful formation of N-GQDs having the average particle size about 8.63 nm. Further, the optical band gap was found to be 4.07 eV, 3.28 eV for N-GQDs, TiO₂ which increases up to 3.69 eV for 80 TiO₂/20 N-GQDs thin film. Also, it has been observed that the prepared thin films are highly transparent in visible region. Further, the temperature dependent I–V characteristics of prepared thin films within the temperature range of 293–513 K and voltage range of 0–60 V depicts the decreased resistivity up to 1.85 × 10⁴ Ω–cm at 513 K from 3.35 × 10⁴ Ω–cm at 293 K of 80 TiO₂/20 N-GQDs thin film. Moreover, the increase in the transparency of 80 TiO₂/20N-GQDs thin film and decreased resistivity up to 1.85 × 10⁴ Ω–cm at 513 K suggests its utilization as a transparent and conducting electrode in optoelectronic devices.