High-sensitivity optical biochemical sensors

Label-free biochemical sensors enable direct detection of biomolecules and analytes based on their physical properties. In addition to their applications in solutions and gas detection, these sensors can serve as affinity-based biosensors, with receptors attached to the sensor surface that interact with analytes. Emerging applications encompass point-of-care blood tests, disease diagnostics, drug testing, environmental monitoring, and food security. Pointof-care systems can be developed to process clinical samples with various biomarkers in diverse working environments. In this thesis, I have designed, simulated, fabricated, and measured integrated optical labelfree biochemical sensors. Four distinct compact sensor designs have been proposed to address sensitivity limitations and the free spectral range (FSR) effect in microring resonators (MRRs), which have significantly advanced the field. I have measured the transmission losses of fabricated optical waveguides, including strip and slot waveguides. Experimental verification of sensitivity performance has been conducted across various parameters. One of the key contributions is the demonstration of the inner-wall grating double slot micro ring resonator (IG-DSMRR) with a 6.72 µm radius, based on the silicon-on-insulator (SOI) platform. This sensor has demonstrated a high measured refractive index (RI) sensitivity in glucose solutions (563 nm/RIU) with a limit of detection (LOD) value of 3.7×10-6 RIU. The achieved bulk sensitivity is more than two times that of optimized designed single strip SOIbased quasi-transverse magnetic (TM) mode MRRs. The concentration sensitivity for sodium chloride solutions reaches 981 pm/%, with a minimum concentration detection limit of 0.02%. The detection range has been significantly extended to 72.62 nm, with a measured Q-factor of 1.6×104 . Transmission losses for straight strip, slot, and double slot waveguides are 0.9 dB/cm, 5.2 dB/cm, and 20.2 dB/cm, respectively. Another significant contribution is the novel sidewall grating slot microring resonator (SGSMRR) with a compact size (5 µm centre radius) on the silicon-on-insulator (SOI) platform. This sensor demonstrates a measured refractive index (RI) sensitivity of 620 nm/RIU and a LOD value of 1.4×10-4 RIU. The concentration sensitivity and minimum concentration detection limit are 1120 pm/% and 0.05%, respectively. Notably, the detection range, based on a grating structure, has been significantly enlarged to 85.8 nm, four times the free spectral range of conventional slot MRRs, with a measured Q-factor of 5.2×103 . The subwavelength grating cascaded microring resonator (SWG-CMRR) structure has been developed, demonstrating high measured sensitivity at 810 nm/RIU, with a LOD value of 2.04×10-4 and a measured Q-factor of 7.7×103 . Additionally, the double slot microring resonator (DSMRR) structure has been fabricated and verified in this project, showcasing a measured RI sensitivity of 600 nm/RIU, a LOD value of 1.15×10-6 , and a measured Q-factor of 2.6×104 . Furthermore, I have undertaken the design, simulation, and fabrication of surface plasmonic sensing structures, such as nanodots and nano rings. These structures enable the detection of hybrid photons and mapping of anapole-like electronic modes using the Polarization Indirect Microscopic Imaging (PIMI) technique

The DKU-DukeECE Diarization System for the VoxCeleb Speaker Recognition Challenge 2022

This paper discribes the DKU-DukeECE submission to the 4th track of the VoxCeleb Speaker Recognition Challenge 2022 (VoxSRC-22). Our system contains a fused voice activity detection model, a clustering-based diarization model, and a target-speaker voice activity detection-based overlap detection model. Overall, the submitted system is similar to our previous year's system in VoxSRC-21. The difference is that we use a much better speaker embedding and a fused voice activity detection, which significantly improves the performance. Finally, we fuse 4 different systems using DOVER-lap and achieve 4.75 of the diarization error rate, which ranks the 1st place in track 4.Comment: arXiv admin note: substantial text overlap with arXiv:2109.0200

The DKU-MSXF Diarization System for the VoxCeleb Speaker Recognition Challenge 2023

This paper describes the DKU-MSXF submission to track 4 of the VoxCeleb Speaker Recognition Challenge 2023 (VoxSRC-23). Our system pipeline contains voice activity detection, clustering-based diarization, overlapped speech detection, and target-speaker voice activity detection, where each procedure has a fused output from 3 sub-models. Finally, we fuse different clustering-based and TSVAD-based diarization systems using DOVER-Lap and achieve the 4.30% diarization error rate (DER), which ranks first place on track 4 of the challenge leaderboard

Optical Fiber LSPR Biosensor Prepared by Gold Nanoparticle Assembly on Polyelectrolyte Multilayer

This article provides a novel method of constructing an optical fiber localized surface plasmon resonance (LSPR) biosensor. A gold nanoparticle (NP) assembled film as the sensing layer was built on the polyelectrolyte (PE) multilayer modified sidewall of an unclad optical fiber. By using a trilayer PE structure, we obtained a monodisperse gold NP assembled film. The preparation procedure for this LSPR sensor is simple and time saving. The optical fiber LSPR sensor has higher sensitivity and outstanding reproducibility. The higher anti-interference ability for response to an antibody makes it a promising method in application as a portable immuno-sensor

Tumor-associated macrophages mediate resistance of EGFR-TKIs in non-small cell lung cancer: mechanisms and prospects

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) are the first-line standard treatment for advanced non-small cell lung cancer (NSCLC) with EGFR mutation. However, resistance to EGFR-TKIs is inevitable. Currently, most studies on the mechanism of EGFR-TKIs resistance mainly focus on the spontaneous resistance phenotype of NSCLC cells. Studies have shown that the tumor microenvironment (TME) also mediates EGFR-TKIs resistance in NSCLC. Tumor-associated macrophages (TAMs), one of the central immune cells in the TME of NSCLC, play an essential role in mediating EGFR-TKIs resistance. This study aims to comprehensively review the current mechanisms underlying TAM-mediated resistance to EGFR-TKIs and discuss the potential efficacy of combining EGFR-TKIs with targeted TAMs therapy. Combining EGFR-TKIs with TAMs targeting may improve the prognosis of NSCLC with EGFR mutation to some extent

Regrowth-free AlGaInAs MQW polarization controller integrated with sidewall grating DFB laser

We report an AlGaInAs multiple quantum well integrated source of polarization controlled light consisting of a polarization mode converter PMC, differential phase shifter(DPS), and a side wall grating distributed-feedback DFB laser. We demonstrate an asymmetrical stepped-height ridge waveguide PMC to realize TE to TM polarization conversion and a symmetrical straight waveguide DPS to enable polarization rotation from approximately counterclockwise circular polarization to linear polarization. Based on the identical epitaxial layer scheme, all of the PMC, DPS, and DFB laser can be integrated monolithically using only a single step of metalorganic vapor phase epitaxy and two steps of III V material dry etching. For the DFB-PMC device, a high TE to TM polarization conversion efficiency 98% over a wide range of DFB injection currents is reported at 1555 nm wavelength. For the DFB-PMC-DPS device, a 60 degree rotation of the Stokes vector was obtained on the Poincar\'e sphere with a range of bias voltage from 0 V to -4.0 V at IDFB is 170 mA.Comment: arXiv admin note: text overlap with arXiv:2210.1051

Stepped-height ridge waveguide MQW polarization mode converter monolithically integrated with sidewall grating DFB laser

We report the first demonstration of a 1555 nm stepped-height ridge waveguide polarization mode converter monolithically integrated with a side wall grating distributed-feedback (DFB) laser using the identical epitaxial layer scheme. The device shows stable single longitudinal mode (SLM) operation with the output light converted from TE to TM polarization with an efficiency of >94% over a wide range of DFB injection currents (IDFB) from 140 mA to 190 mA. The highest TM mode purity of 98.2% was obtained at IDFB=180 mA. A particular advantage of this device is that only a single step of metalorganic vapor-phase epitaxy and two steps of III-V material dry etching are required for the whole integrated device fabrication, significantly reducing complexity and cost

Scattering Field Enhanced Biosensing Based on Sub-wavelength Split-ring Plasmonic Cavity With High Q-factor

Plasmonic structures are widely used in modern biosensor design. various plasmonic resonant cavities could efficiently achieve a high Q-factor, improving the local field intensity to enhance photoluminescence or SERS (Surface-Enhanced Raman Scattering) of small molecules. Also, the combination between virus-like particles and plasmonic structures could significantly influence the scattering spectrum and field, which is utilized as a method for biological particle detection. In this paper, we designed one kind of gold plasmonic cavity with the shape of a split-ring. An edge gap and a bonus center bulge are introduced in the split-ring structure. Our simulation is based on Finite Difference Time Domain (FDTD) method. Polarization Indirect Microscopic Imaging (PIMI) technique is used here to detect far-field mode distribution under the resonant wavelength. The simulation results demonstrate resonant peaks in the visible spectrum at about 600 nm with a Q-factor reaches to 74. Localized hot spots are generated by an edge dipole mode and a cavity hexapole mode at resonant wavelength, which is according to dark points in the PIMI sinδ image. Also, the split-ring cavity shows a sensitivity when combined with biological particles. The scattering distribution is evidently changed as a result of energy exchange between particles and split-ring cavity, indicating a promising possibility for biosensing

Stepped-height ridge waveguide MQW polarization mode converter monolithically integrated with sidewall grating DFB laser

We report the first demonstration of a 1555 nm stepped-height ridge waveguide polarization mode converter monolithically integrated with a side wall grating distributed-feedback (DFB) laser using the identical epitaxial layer scheme. The device shows stable single longitudinal mode (SLM) operation with the output light converted from TE to TM polarization with an efficiency of >94% over a wide range of DFB injection currents (IDFB) from 140 mA to 190 mA. The highest TM mode purity of 98.2% was obtained at IDFB=180 mA. A particular advantage of this device is that only a single step of metalorganic vapor-phase epitaxy and two steps of III-V material dry etching are required for the whole integrated device fabrication, significantly reducing complexity and cost

Dual-wavelength DFB laser array based on sidewall grating and lateral modulation of the grating coupling coefficient

A monolithic dual-wavelength DFB laser array based on sidewall gratings and a novel modulation of the grating coupling coefficient is proposed and demonstrated experimentally. The grating coupling coefficient distribution along the cavity is modulated by changing the alignment between the gratings on the two sidewalls. The frequency difference between the two lasing modes can be modulated by changing the cavity length and grating recess depth. A series of microwave signals in the range of 50 GHz to 59 GHz is observed after beating the two optical lines in a photodetector. The measured optical linewidths are 250 kHz and 850 kHz when the cavity length is 1200 μm and 1000 μm, respectively