Biomaterial, such as proteins and deoxyribonucleic acid (DNA), which have many advantages such as biocompatibility and biodegradability, have been widely adopted as photonic device materials. In this study, we proposed and experimentally demonstrated an all-biomaterial whispering-gallery-mode (WGM) microbottle resonator. The quality factor of the fabricated protein microbottle resonator is on the order of 105. In addition, the entire process for preparing microbottle is simple and low-cost. Our work will open a door to explore various biomaterial and different bio-photonic device for biomedical applications.
We fabricated a polydimethylsiloxane (PDMS)-coated silica microbubble cavity with rich whispering gallery modes (WGMs). An electromagnetically induced transparency (EIT) window is realized through experimentally coupling a tapered fiber with the PDMS-coated microbubble resonator (MBR). There is a high-Q mode in the vicinity of a low-Q mode in transmission spectra. The experimental results prove that the high-Q mode performs a small redshift while the low-Q mode performs a large blueshift when the input power increases. This attributes to the negative thermo-optical coefficient (TOC) of PDMS and the positive TOC of silica. An EIT-like window is realized when these two modes are on-resonance with same frequency.
A packaged microbubble resonator with an outer diameter of 210 μm and wall thickness around 3 Μm has been fabricated which can achieve a sensitivity of 71 nm/RIU for refractive index measurement. We further propose it for laser wavelength monitoring with excellent performance verified for both low and high power laser inputs. Combined with the self-referenced differential-mode technique, we can measure the laser wavelength drift of 0.35 pm at low power level and 0.07 pm at high power level, respectively.
We experimentally demonstrate a high sensitivity temperature sensor based on packaged microdroplet whispering gallery mode (WGM) resonator. Fabrication process of the packaged microdroplet resonator is easy and controllable. The sensitivity and the electric field intensity distribution of different radial modes are calculated and analyzed by Mie theory. The measured temperature sensitivity is over 200 pm/ °C, due to the mode distribution of microdroplet resonator and high thermo-optic coefficient of dimethyl sulfoxide (DMSO). The proposed packaged microdroplet resonator has the superiority in the high sensitivity and robust property, which exhibit good potential in regards to future integrated photonic devices based sensors.
Luneburg-sphere (LS) is a spherically symmetric sphere with three-dimensional graded-refractive-index structure which can focus parallel beam to a perfect point on the sphere surface. Recent research shows that microsphere can generate super-resolution focusing beyond diffraction limit. Herein a quasi-Luneburg-lens can be used as an optically transparent microsphere for the super-resolution imaging. In this paper, the finite element model is used to investigate the optical properties of the Luneburg-lens. Our simulation results demonstrated that its focus size is below the conventional diffractive limit in the visible spectrum. An effective method of application of a quasiLuneburg-lens is proposed and discussed. Besides super-resolution imaging, Luneburg-lens have the potential applications in nanolithography, nanomedicine areas as well.
We proposed and theoretically investigated a hybrid plasmonics waveguide consisting of a tiptilted quadrate nanowire, which was embedded in a low-permittivity dielectric and placed on a metal substrate with a small gap distance. Due to the corner effect, the hybrid mode with extremely local field enhancement has the long propagation length and strong coupling strength between the dielectric nanowire and metal. By employing the simulations with different geometric parameters, the proposed waveguide can obtain better performances than the previous hybrid plasmonics waveguide, particularly in the subwavelength confinement (as small as λ2/1600), long-range propagation (millimeter range), and optical trapping forces (2.12 pN/W). The use of a naturally dielectric wedge tip of quadrate nanowire that can be chemically synthesized provides an efficient approach to circumvent the fabrication difficulty of shape wedge tips. The present structure provides an excellent platform for nanophotonic waveguides, nanolasers, nanoscale optical tweezers, and biosensing.
Microlasers based on high-Q whispering-gallery-mode (WGM) resonances are promising low-threshold laser sources for bio-sensing and imaging applications. In this talk, we demonstrate a cost effective approach to obtain size-controllable polymer microspheres, which can be served as good WGM microcavities. By injecting SU-8 solution into low-refractiveindex UV polymer, self-assembled spherical droplet with smooth surface can be created inside the elastic medium and then solidified by UV exposure. The size of the microspheres can be tuned from several to hundreds of microns. WGM Lasing has been achieved by optically pumping the dye-doped microspheres with ns lasers. Experimental results show that the microsphere lasers have high quality factors and low lasing thresholds. The self-assembled dye-doped polymer microspheres would provide an excellent platform for the micro-laser sources in on-chip biosensing and imaging systems.
We report that by using a single mode coupled microcavity laser, we successfully realized a sensitivity of 80 pg/ml for
detecting BSA. The detecting scheme also works for other bio samples. The result proves that active sensing with
microcavity laser can achieve ultrahigh sensitivity. Further analysis shows that the ultra-sensitivity comes from the slight
change of coupling coefficient between the two coupled microcavities.
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