Researchers from Iran have developed tunable narrow single-mode bandpass optical filters using graphene nanoribbons (GNRs) for terahertz (THz) applications, potentially transforming optical communication networks with high-speed, low-loss data transmission. The study, published in Scientific Reports, focuses on using a Nano Spraying Technique (NST) to enhance the durability and functionality of these filters.
Image Credit: 3DStach/Shutterstock.com
Background
The development of optical devices has transformed optical communication, leading to faster networks. The growing demand for high-speed data transmission has highlighted the need for devices that can precisely control and enhance efficiency in the THz frequency range.
Graphene, a two-dimensional carbon material, has emerged as a promising nanomaterial due to its exceptional electronic, optical, and mechanical properties. Its ability to manipulate optical parameters makes it a valuable tool in optoelectronics, mainly in the THz spectrum.
Extensive research has explored graphene-based devices for applications in biology, medicine, imaging, sensing, and telecommunications. Despite its potential, the lack of suitable materials has limited progress in the THz frequency range, making graphene a key candidate for further research and development in optoelectronics.
About the Research
The researchers designed and investigated a tunable narrow single-mode bandpass filter using GNRs.
The filter, operating in the THz frequency range, was constructed in three steps, incorporating two input/output waveguides and a T-shaped resonator at the nanoscale. Three-dimensional finite difference time domain (3D-FDTD) simulations and coupled mode theory (CMT) were used to analyze the filter's performance and achieve tunability by adjusting the nanoribbon size and graphene's chemical potential.
The initial filter design featured a plus-shaped resonator but exhibited low transmission efficiency and unwanted extra modes. To address these issues, researchers introduced a gap between the input waveguide, resonator, and output waveguide. They then developed an E-shaped resonator, which successfully eliminated the extra harmonics and generated a single-mode signal over a broad frequency range.
The final design resulted in a tunable narrow single-mode bandpass filter that optimized transmission efficiency while maintaining a precise single-mode signal.
The study combined theoretical and numerical methods, using FDTD to simulate the filter's performance under various conditions. FDTD, a technique for solving Maxwell's equations, simulated the interaction between GNRs and electromagnetic waves, while a graphene-based model simulated GNR behavior. Additionally, the parameters, such as transmission spectrum, frequency, full width at half maximum (FWHM), and quality factor (Q-factor), were used to evaluate the performance.
Key Findings
Simulation results showed that the proposed filter achieved a peak transmission efficiency of 99 %, a Q-factor of 100, a FWHM of 0.115 THz at 11.5 THz, and a free spectral range (FSR) of 45 THz. Additionally, the transmission spectrum, calculated using CMT, closely matched the results from the 3D-FDTD simulations.
The researchers also studied the impact of varying graphene's chemical potential on the filter's frequency response. By applying a gate voltage, they adjusted the chemical potential, which altered graphene’s surface conductivity and subsequently modified the filter’s transmission spectrum.
Additionally, the study explored the effects of adjusting the length of the L3 nanoribbon and creating gaps in the device structure optimized performance. It demonstrated that the filter's behavior was highly sensitive to the width and gaps of the GNRs, with small changes significantly impacting its performance.
The influence of the substrate's refractive index on the filter's resonance frequency was also investigated. The filter showed a sensitivity of 4.5 THz per Refractive Index Unit (RIU) and 12,290 nm/RIU, indicating its potential for sensing applications. The authors highlighted that the surface conductivity of the GNRs played a crucial role in determining the filter’s performance, with even small changes having a significant effect.
Applications
The developed filters have significant potential for various applications in the THz frequency range. With high transmission efficiency, narrow bandwidth, and tunability, they are ideal for integrated optical components and compact optical devices. These filters can be used in high-speed data transmission, optical communication networks, and sensing devices, with additional potential for biomedical applications like imaging and sensing.
This advancement could revolutionize optoelectronics by enabling high-speed, low-loss optical communication networks. The filter’s sensitivity to changes in the substrate’s refractive index also makes it a promising sensor for detecting gasses, chemicals, and biological substances. Additionally, it can be utilized in THz imaging, which is valuable for security screenings, medical diagnostics, and optical telecommunication receivers.
Conclusion
The novel optical filter proved effective for THz applications using GNRs, demonstrating impressive performance metrics such as high transmission efficiency, a high Q-factor, narrow FWHM, and high sensitivity. The ability to tune its frequency response by adjusting graphene’s chemical potential and optimizing the device structure makes it a versatile tool for various applications in optical communication, sensing, and imaging.
Future work should focus on enhancing the tunability and efficiency of graphene-based optical filters by exploring new materials and fabrication methods. Additionally, it will be important to integrate these filters into more complex optical systems and evaluate their performance in real-world applications, such as telecommunications and medical diagnostics.
Discover More: Latest Breakthroughs in Graphene Research
Journal Reference
Mohammadi, G., et al. (2024). A tunable narrow single-mode bandpass filter using graphene nanoribbons for THz applications. Sci Rep. DOI: 10.1038/s41598-024-71869-3, https://www.nature.com/articles/s41598-024-71869-3
Disclaimer: The views expressed here are those of the author expressed in their private capacity and do not necessarily represent the views of AZoM.com Limited T/A AZoNetwork the owner and operator of this website. This disclaimer forms part of the Terms and conditions of use of this website.