Ultra-High Sensitive Optofluidic Whispering-gallery-Mode (WGM) Microcavity Bio/Chemical Sensors

Bio/chemical sensor is the indispensable part for the bio/chemical detection. There is currently a great deal of interest in bio/chemical sensors based on optofluidic whispering gallery mode (WGM) microcavity, due to their unique advantages of small size, small sample volumes consumption, real time detection, fast response, high sensitivity and low detection limit. In this thesis, in order to improve the sensitivity and detection limit of bio/chemical sensing, novel sensing mechanisms for optofluidic WGM microcavity based bio/chemical sensors are investigated and developed.The main achievements are as follow:1. Multi-cavity-coupled structure is employed to enhance the side-mode suppression ability of WGM microcavity laser. On this basis, coupled-WGM-microcavity lasers are investigated for sensing, and a new sensing scheme based on the modulation evelope shift of coupled-WGM-microcavity laser spectra is proposed, which breaks the theoretical limits of single-microcavity sensocs by one order higher. By combining intra-cavity detection and Vernier effect to enhance sensitivity, a new chemical sensor based on optofluidic coupled-WGM-microcavity laser is demonstrated, the sensitivity is up to 5930 nm/RIU, and the detection limit can be as low as 10-7RIU.2. Optofluidic coupled-microbottle-resonator are used to detect biomolecule, and 2 pg/mL HIV-1 p24 antigen is experimentally detectable with a noise equivalent detection limit (NEDL) around 140 fg/mL. Differential mode sensing is proposed and used to suppress noises, and the signal-to-noise ratio (SNR) of detection of 1 pg/mL bovine serum albumin (BSA) is enhanced up to 104 with a NEDL of 10 fg/mL (-0.15 fM). With the help of field enhancement of localized surface plasmon resonance (LSPR), the sensitivity of single nanoparticle detection is increased by 16 times, and single polystyrene (PS) nanoparticle (R=50 nm) is experimentally detectable.3. To enhance the sensitivity of biomolecule conformational changes detection, a new sensing scheme via bioinspired optofluidic ring resonator lasers is proposed. Compared with the traditional fluorescence resonance energy transfer (FRET) method, the sensitivity for the DNA conformational changes detection and protein-protein interation detection is increased by 16 times and 21 times, respectively.