Search

The emergences of silicon-based photonic crystal (PhC) waveguides and two-dimensional (2D) PhC line-defect optical cavities have revolutionized the field of integrated photonics. In this paper, we design and fabricate a high-quality (high-Q) 2D silicon-based PhC optical cavity with integrated waveguides. We employ the 2D finite-difference time-domain (FDTD) method to simulate the cavity, considering two different thicknesses: 0.5 μm and 0.25 μm. By optimizing the line-defect and air-slot widths for the integrated PhC waveguides, we are able to achieve remarkable Q-factors for the PhC optical cavity. With a silicon thickness of 0.5 μm, the high-Q achieves an impressively high value of 8.01 × 106, while at a silicon thickness of 0.25 μm, it achieves 1.91 × 107. This research highlights the importance of design optimization and fabrication techniques in achieving high-Q optical devices using PhC and silicon-based structures. [ABSTRACT FROM AUTHOR]

The conventional circular waveguide 90° TE01 bend makes it difficult to achieve broadband because of the serious interference from TM11 mode. To solve this problem, the mode coupling characteristics in the hexagonal waveguides are investigated in this paper, and it is found that when the deformation amplitude is appropriate, not only the degradation between TE01 and TM11 is broken but other parasitic modes can be efficiently suppressed. Based on the analysis, an oversized broadband TE01 waveguide bend with variable curvature is proposed, and its transmission efficiency is over 95% from 8.5 to 11 GHz, while its structure length is only 26.16 times wavelength. Measurement results indicate that the S21 of the bend is about −0.4 dB from 8.5 to 11 GHz, and it works stably under a microwave output power of 1 MW. The consistency between theoretical calculations, simulation, and experiments indicates the feasibility of this novel TE01 bend. [ABSTRACT FROM AUTHOR]

Addressing the challenges of passive Radio Frequency Identification (RFID) indoor localization technology in Non-Line-of-Sight (NLoS) and multipath environments, this paper presents an innovative approach by introducing a combined technology integrating an improved Kalman Filter with Space Domain Phase Difference of Arrival (SD-PDOA) and Received Signal Strength Indicator (RSSI). This methodology utilizes the distinct channel characteristics in multipath and NLoS contexts to effectively filter out interference and accurately extract localization information, thereby facilitating high precision and stability in passive RFID localization. The efficacy of this approach is demonstrated through detailed simulations and empirical tests conducted on a custom-built experimental platform consisting of passive RFID tags and an R420 reader. The findings are significant: in NLoS conditions, the four-antenna localization system achieved a notable localization accuracy of 0.25 m at a distance of 5 m. In complex multipath environments, this system achieved a localization accuracy of approximately 0.5 m at a distance of 5 m. When compared to conventional passive localization methods, our proposed solution exhibits a substantial improvement in indoor localization accuracy under NLoS and multipath conditions. This research provides a robust and effective technical solution for high-precision passive indoor localization in the Internet of Things (IoT) system, marking a significant advancement in the field. [ABSTRACT FROM AUTHOR]

When the radio frequency identification (RFID) system inventories multiple tags, the recognition rate will be seriously affected due to collisions. Based on the existing dynamic frame slotted Aloha (DFSA) algorithm, a sub-frame observation and cyclic redundancy check (CRC) grouping combined dynamic framed slotted Aloha (SUBF-CGDFSA) algorithm is proposed. The algorithm combines the precise estimation method of the quantity of large-scale tags, the large-scale tags grouping mechanism based on CRC pseudo-random characteristics, and the Aloha anti-collision optimization mechanism based on sub-frame observation. By grouping tags and sequentially identifying them within subframes, it accurately estimates the number of remaining tags and optimizes frame length accordingly to improve efficiency in large-scale RFID systems. Simulation outcomes demonstrate that this proposed algorithm can effectively break through the system throughput bottleneck of 36.8%, which is up to 30% higher than the existing DFSA standard scheme, and has more significant advantages, which is suitable for application in large-scale RFID tags scenarios. [ABSTRACT FROM AUTHOR]

For the sensitive high-resolution force- and field-sensing applications, the large-mass microelectromechanical system (MEMS) and optomechanical cavity have been proposed to realize the sub-aN/Hz1/2 resolution levels. In view of the optomechanical cavity-based force- and field-sensors, the optomechanical coupling is the key parameter for achieving high sensitivity and resolution. Here we demonstrate a chip-scale optomechanical cavity with large mass which operates at ≈77.7 kHz fundamental mode and intrinsically exhibiting large optomechanical coupling of 44 GHz/nm or more, for both optical resonance modes. The mechanical stiffening range of ≈58 kHz and a more than 100th-order harmonics are obtained, with which the free-running frequency instability is lower than 10-6 at 100 ms integration time. Such results can be applied to further improve the sensing performance of the optomechanical inspired chip-scale sensors.