Nanophotonic structures can enhance light-mater interaction at nanoscales helping to improve the detection sensitivity of biosensors. In this work, we present a sandwich-type immunosensor by combining a nanophotonic resonant waveguide grating (RWG) structure and upconverting nanoparticles (UCNPs). UCNPs are used to label a target biomarker captured by capture antibody molecules immobilized on the surface of the RWG structure, which is used to enhance the upconversion fluorescence (UCF) of UCNPs through excitation resonance. The immunosensor has an extremely low limit of detection (LOD) in sub-fg/mL level and a detection range of six orders of magnitude and can be used to detect a variety of biomarkers such as cardiac troponin I, tau protein and phosphated-tau protein, etc. The LOD of the immunosensor is greatly reduced due to the increased UCF of UCNPs and the reduction of nonspecific adsorption of detection antibody-conjugated UCNPs on the RWG substrate surface.
KEYWORDS: 3D optical data storage, Super resolution, 3D image processing, Objectives, Photonic crystals, Data storage, Absorption, Microfabrication, 3D microstructuring, Multiphoton processes
Different types of objective lens (OL), i.e. circular, annular and one-dark-ring, are proposed and demonstrated to control the aspect ratio (AR) of micro-focus-region of high numerical aperture (NA) OL. Namely, the AR decreases from about 7.3 to 2.7 in case of using a circular OL with NA changes from 0.7 to 1.4, respectively. By using an annular OL, the transverse size of the focal spot of micro-focus-region decreases but its longitudinal size increases, so that the AR increases several times with respect to the case of circular OL. In particular, when using the one-dark-ring OL, one can decrease both transverse and longitudinal sizes of the focal spot or decrease only the longitudinal size, so that the AR obtained with a one-dark-ring OL is decreased to about 70% of that obtained with a circular OL. Such lenses can be useful for many applications such as sub-microfabrication and three-dimensional data storage using multi-photon absorption process.
We demonstrate a promising method to fabricate large-area photonic crystals with desired defects by using the combination of interference and multi-photon polymerization techniques. Multiple-exposure of two-beam interference pattern at 325 nm into a negative SU-8 photopolymerizable photoresist is used to form a square or hexagonal twodimensional periodic structure. Arbitrary defects are introduced in these structures by tightly focused (numerical aperture 0.85) 100 fs duration pulses at 830 nm to generate multi-photon polymerization effect. The experimental evidence of 6 mm × 6 mm photonic crystals with the lattice constant as small as 1 μm embedding several kinds of defect proves the concept and shows this technique potentially useful for photonic researches and applications.
A simple optical interference method for fabricating two- and three-dimensional (2D and 3D) periodical structures is theoretically and experimentally demonstrated. Multiple-exposure of two-beam interference pattern into a photopolymerizable resist creates high quality 2D or 3D microstructures. The type of periodic structure depends on the orientation of the photoresist with respect to the laser beams and the number of exposure. Square or hexagonal structures are obtained by choosing an angle of 90° or 60°, respectively, between two different exposures. 2D structures are obtained with two or three equal exposures. 3D structures with different types (bcc, fcc, Woodpile, etc.) are obtained with three or four exposures and appropriate rotation angles. This method presents many advantages over others using multi-beam (three-, four-, or five-beam) interference: i) easy to fabricate different structures(hexagonal or square) by simply rotating the sample, ii) best contrast between the minimal and maximal intensities of interference pattern due to the identical polarization of two laser beams in the interference area, iii) in particular, 3D periodical structures have the same period in three dimensions, which can't be obtained by one exposure of multi-beam interference. The experimental results obtained with SU-8 negative photoresist are well in agreement with the theoretical predictions. Such fabrication technique can be useful for applications in photonic crystals research.
Photoreactive third-harmonic (TH) generation at 355 nm in diarylethene- polymethylmethacrylate (DE-PMMA) polymer thin films is obtained by either one- or two-photon excitation. TH intensity generated from a DE-PMMA polymer thin film decreases, when it is pumped by either 325 nm or 442 nm, which change molecular structure of DE molecules from open-form (A form) to closed-form (B form). TH intensity recovers to its original intensity level, after all B form DE molecules return to A form induced by 532 nm or 1064 nm laser irradiation. The experimental results reveal that the second-order hyperpolarizability (γ) of A form molecules may be larger than that of B form molecules. Moreover, TH output efficiency is independent of the angle between the pump and probe polarization directions. Those experimental results were explained by using a photoinduced isomerization theory based angular hole burning and angular redistribution mechanisms for two-dimensional structure of DE molecules including the two-photon absorption effect of B form. The simulation results are consistent with those of optical pumping TH experiment.
Temperature effect on photoinduced third harmonic generation (THG) variation of an azo copolymer and an azo guest-host polymer is studied at two different temperatures. At higher temperature, both angular hole burning (AHB) and molecule angular redistribution (AR) motions are smaller due to the decrease of cis-trans thermal relaxation time and cis population. Smaller photoinduced THG change is observed in both samples at higher temperature. THG recovery experiment results show copolymer thin films pumped at high temperature have the best photoinduced THG variation stability after turning off the pump beam.
The first hyperpolarizabilities ((beta) ) of an azulenic donor-acceptor chromophore at different wavelengths were measured by a tunable wavelength hyper-Rayleigh scattering (HRS) experiments. The (beta) values measured at different wavelengths are used to investigate the dispersion relation of one-dimensional charge transfer organic chromophores. The validity of the well known un-damped two-level model and some modified models which include the damping and the vibronic effects are discussed.
Multiple Quantum Well (MQW) materials and devices have been designed and demonstrated to have large optical nonlinearities which are suitable for use in ultrafast optical TDMA interconnects at 1.3 micrometers . The MQW materials consist of GaAlInAs wells and AlInAs barriers grown lattice-matched to a semi-insulating InP substrate by molecular beam epitaxy. The MQW samples exhibited large absorption changes at 1.3 micrometers due to bandfilling and exchange effects. The carrier saturation densities near the heavy-hole exciton peak were similar to those for GaAs/AlGaAs MQWs. The large optical nonlinearities near 1.3 micrometers were used to demonstrate an all-optical, high-contrast asymmetric reflection modulator suitable for performing all-optical time-division demultiplexing at low pump intensities. The modulator consists of an asymmetric Fabry-Perot etalon which utilizes a nonlinear MQW spacer. The modulator exhibited an on/off contrast ratio of greater than 1000:1 and an insertion loss of 2.2 dB at a pump intensity of 30 kW/cm2. The recovery of the modulator is shown to decay with a time-constant of 725 ps.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.