Targeting at a low cost and accessible diagnostic device in clinical practice, a compact surface plasmon resonance (SPR) biosensor with a large dynamic range in high sensitivity is designed to satisfy commercial needs in food safety, environmental bio-pollution monitoring, and fast clinical diagnosis. The core component integrates an optical coupler, a sample-loading plate, and angle-tuning reflectors is injection-molded as a free-from prism made of plastic optics. This design makes a matching-oil-free operation during operation. The disposability of this low-cost component ensures testing or diagnosis without cross contamination in bio-samples.
For the purpose of point of care (POC), a disposable polymer-molding prism with two parabolic side surfaces is employed for the ultra compact SPRI biosensor. A compact SPRI biosensor downsized to a form factor of 20 cm *15 cm*5 cm with extremely high sensitivity and large dynamic range is proposed in this study. With the cost effective and disposable polymer-molding prism design, the cross contamination between samples can be avoided. In this demonstration, we integrated the CCD detection system and multichannel fluidic system into this device that allows users to quickly screen various samples simultaneously.
Laser velocimetry capable of measuring nanoscale motion or displacement normal to vibrational surface is always important in industry and scientific applications. However, measurement sensitivity down to sub-nanometer scale is always a challenge, and utilization of lock-in amplifiers is unavoidable. Measurement is then also limited to single-point detection. Here we report a laser Doppler velocimetry capable of non-contact detection in sub-nanometer scale down to sub-Hertz frequency in a Mach-Zehnder configuration without lock-in amplifiers. Environment perturbation in tens of nanometer scale can be removed by empirical mode decomposition. Lack of lock-in amplifiers promises this technology not limited to single-point detection.
With the development of a point of care (POC) biosensor in mind, a polymer-molding prism with double parabolic
surfaces is invented and developed to implement an ultra-compact SPR biosensor with extremely high sensitivity. The
polymer molded parabolic prism is cost effective and disposable, thus cross contamination between biological samples
can be avoided. A highly sensitive biosensor with a form factor less than 15cm*15cm*5cm was received with a tunable
excitation angle of light beam for a large dynamic range. A highly sensitive optical phase interrogation was
demonstrated. The biosensor is also compatible to a modern microscopy platform.
Subgingival calculus has been recognized as a major cause of periodontitis, which is one of the main chronic infectious diseases of oral cavities and a principal cause of tooth loss in humans. Bacteria deposited in subgingival calculus or plaque cause gingival inflammation, function deterioration, and then periodontitis. However, subgingival calculus within the periodontal pocket is a complicated and potentially delicate structure to be detected with current dental armamentaria, namely dental x-rays and dental probes. Consequently, complete removal of subgingival calculus remains a challenge to periodontal therapies. In this study, the detection of subgingival calculus employing a multiphoton autofluorescence imaging method was characterized in comparison with a one-photon confocal fluorescence imaging technique. Feasibility of such a system was studied based on fluorescence response of gingiva, healthy teeth, and calculus with and without gingiva covered. The multiphoton fluorescence technology perceived the tissue-covered subgingival calculus that cannot be observed by the one-photon confocal fluorescence method.
We proposed an innovative phase interrogation method for localized surface plasmon resonance (LSPR) detection.
To our knowledge, this is the first demonstration of LSPR biosensor by phase interrogation. LSPR is realized as the
plasmonic resonance within confined metal nanoparticle. Nanoparticle couples the light by means of a non-radiative
inter-band absorption, and a scattering from surface plasmon oscillation, the total contribution is the optical
extinction of nanoparticles. Due to the variety of resonance types, LSPR is extensively studied in the field of
biological sensing, imaging, and medical therapeutics. Generally, LSPR is probed by optical intensity variation of
continuous wavelength, in other words, wavelength interrogation. LSPR sensitivity probed by this method is ranged
from several tens nm/RIU to less than 1000nm/RIU depending on the nanostructure and metal species, which at least
an order of magnitude less than conventional SPR biosensor in wavelength interrogation. In this work, an innovative
common-path phase interrogation system is applied for LSPR detection. Phase difference in our home-made system
is simply extracted through the correlation of optical intensity under different polarization without any heterodyne
optical modulator or piezoelectric transducer, and thus low down the cost and complexity in optical setup. In
addition, signal-to-noise ratio is substantially reduced since the signal wave and reference wave share the common
path. In our preliminary results, LSPR resolution of Au nanodisk array is 1.74 x 10-4 RIU by wavelength
interrogation; on the other side, LSPR resolution of Au nanodisk array is 2.02x10-6 RIU in phase interrogation.
LSPR sensitivity is around one order of magnitude enhanced. In conclusion, we demonstrated that LSPR sensitivity
can be further enhanced by phase interrogation.
Surface plasmon resonance (SPR) biosensors have been widely used for dynamical analysis of molecular affinity,
bacterium screening, and drug discovery due to its advantages of label-free detection, dynamic interaction analysis, small
sample volume, and ultra sensitivity (feasibility of single molecular detection). Recently, SPR biosensing for cell
imaging known as SPR microscopy (SPRM) has attracted great attention due to the characteristics of SPR biosensors.
However, it is well known that the trends of sensitivity and spatial resolution are opposite to each other: Surface plasmon
waves (SPWs) with shorter wavelength which provides higher spatial resolution has less sensitivity. It is known that the
spatial resolution of SPRM is limited by the propagation length of surface plasmon wave (SPW) along the metaldielectric
interface. SPW excited by 632.8 nm light has the propagation length of 3 um. This length becomes longer
when a longer wavelength is selected. While most of SPR biosensors are built with 632.8 nm or longer wavelength for
high sensitivity, using 532nm light to excite SPWs is desired for submicron resolution since the propagation length is
around 150 nm. Different from current phase interrogation methods, the proposed phase interrogation method is highly
sensitive and suitable for CCD imaging. Although it is generally believed that SPWs with wavelength 532nm has poor
sensitivity, the experimental result showed that the setup can reach the sensitivity lower than 2×10-6 RIU when
sucrose is used as the test sample.
An antimicrobial testing method using surface plasmon resonance to improve the present techniques is reported
in this paper. Different from conventional methods, namely Kirby-Bauer disk diffusion and variations of broth
microdilution, the examination time is reduced from 18-24 hours or more to less than one hour after the
treatment of antibiotics. E-coli resistant and susceptible to ampicillin are used in the test to demonstrate this
innovative method. It is generally known that discovering a method to exam the bacterium resistance rapidly
and correctly is very important for patients and for preventing infective disease from spreading. The method
reported can benefit this requirement.
A direct experimental observation of chaotic synchronous scenarios, namely chaotic optical modulation, is demonstrated in a unidirectional chaotic-coupling semiconductor laser system. In this fully optical system, the channel signal is different from the output field of the transmitter laser by an additional monochromatic optical field. Different from the chaos synchronization explainable by theory of chaos synchronization, the output field of the receiver laser is not synchronized to that of the transmitter laser. Instead, it is synchronized to the channel signal. However, the optical frequency of the receiver is not locked to that of the transmitter. It is observed that not only is the intensity of the receiver output is synchronized to that of the channel signal, but also the chaotic slowly-varying phase of the receiver. The synchronization of the slowly-varying phase is verified by optical interference between the output of the receiver and the channel signal, and the interference result is recorded through a photodetector.
An experimental demonstration of the chaotic synchronization between two injection-locked semiconductor lasers is reported in this paper. Optical injection on the semiconductor laser not only generates optical chaotic output, but also broadens the bandwidth up to two fold of the laser intrinsic bandwidth. Since the chaotic synchronization based on this system is very sensitive to optical phase, the synchronization quality subject to both phase match and phase mismatch is measured in both time and frequency domains. The synchronization quality of each case is quantitatively expressed by the correlation coefficient.
For chaotic optical communications using semiconductor lasers, synchronization of the chaotic waveforms of two semiconductor lasers, one functioning as the transmitter and the other as the receiver, has to be accomplished. Two systems of single-mode semiconductor lasers that exhibit chaotic behavior are considered. A single-mode semiconductor laser with optical injection follows a period-doubling route to chaos, whereas one with delayed optoelectronic feedback follows a quasiperiodic route to chaotic pulsing. The strategy for devising a scheme for synchronizing two semiconductor lasers is to make the coupled transmitter and receiver lasers to be described by two sets of dynamical equations of identical form. The transmitter and receiver are coupled through a signal and are both driven by a force that is a function of the signal. Any message to be communicated can be encoded in the signal. Schemes for synchronization with unidirectional coupling are devised, modeled, and studied for both optical injection and optoelectronic feedback systems. Experimental data on the synchronization of both systems are presented. Methods for encoding and decoding messages are also discussed for both systems.
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