The guided-mode resonance (GMR) sensor operates with quasi-guided modes induced in periodic films. The resonance is enabled by 1D or 2D nanopatterns that are expeditiously fabricated. Optical sensors are needed in many fields including medical diagnostics, chemical analyses, and environmental monitoring. Inducing resonance in multiple modes enables extraction of complete bioreaction information including the biolayer thickness, biolayer refractive index, and any change in the refractive index in the background buffer solution. Thus, we refer to this version of the GMR sensor as the complete biosensor. We address the fundamentals, state of technological development, and implementation of this basic sensor modality.
We initiate a fundamental study of modal-plasmonic interactions in nanostructured resonance elements with the aim to develop new hybrid multiparametric sensors. The proposed hybrid sensor operates under guided-mode resonance (GMR) and surface-plasmon resonance (SPR) in unison. Numerical simulations of gold-integrated periodic resonant films show effective spectral conversions due to interplay between these mechanisms. In some cases, we find enhancements in sensitivity and attendant reduced resonance linewidths improving sensor resolution. Initial experimental results incorporating modal-plasmonic interactions in a resonant system containing a dielectric grating on a thin gold film agree qualitatively with theory. The research is important as the SPR and GMR concepts are independently the basis for commercial sensor systems with major economic impact.
Ovarian carcinoma has the highest lethality rate of gynecologic tumors, largely attributed to the late-stage diagnosis of the disease. Reliable tools for both accurate diagnosis and early detection of disease onset are lacking, and presently less than 20% of ovarian cancers are detected at an early stage. Protein biomarkers that allow the discrimination of early and late stages of ovarian serous carcinomas are urgently needed as they would enable monitoring pre-symptomatic aspects of the disease, disease progression, and the efficacy of intervention therapies. We compare the absolute and relative protein levels of six protein biomarkers for ovarian cancer in five different established ovarian cancer cell lines, utilizing both quantitative immunoblot analysis and a guided-mode resonance (GMR) bioassay detection system that utilizes a label-free optical biosensor readout. The GMR sensor approach provided highly accurate, consistent, and reproducible quantification of protein biomarkers as validated by quantitative immunoblotting, as well as enhanced sensitivity, and is therefore suitable for quantification and detection of novel biomarkers for ovarian cancer. We identified fibronectin, apolipoprotein A1, and TIMP3 as potential protein biomarkers for the differential diagnosis of primary versus metastatic ovarian carcinoma. Future studies are needed to confirm the suitability of protein biomarkers tested herein in patient samples.
Resonant leaky modes can be induced on dielectric, semiconductor, and metallic periodic layers patterned in one or two
dimensions. In this paper, we summarize their physical basis and present their applicability in photonic devices and
systems. The fundamental amplitude and phase response of this device class is presented by computed examples for TE
and TM polarizations for lightly and heavily spatially modulated gratings. A summary of potential applications is
provided followed by discussion of representative examples. In particular, we present a resonant polarizer enabled by a
single periodic silicon layer operating across 200-nm bandwidth at normal incidence. Guided-mode resonance (GMR)
biosensor technology is presented in which the dual-polarization capability of the fundamental resonance effect is
applied to determine two unknowns in a biodetection experiment. In principle, using polarization and modal diversity,
simultaneously collected data sets can be used to determine several relevant parameters in each channel of the sensor
system; these results exemplify this unique capability of GMR sensor technology. Applying the GMR phase, we show
an example of a half-wave retarder design operating across a 50-nm bandwidth at λ~1550 nm. Experimental results
using a metal/dielectric design show that surface-plasmon resonance and leaky-mode resonance can coexist in the same
device; the experimental results fit well with theoretical simulations.
A high-accuracy biosensor system has been developed to provide rapid detection of biomarker proteins as indicators
of ovarian cancer. This photonic detection system is based upon guided-mode resonance sensor technology. The buildup
of the attaching biolayer can be monitored directly, without use of chemical tags, by following the corresponding
resonance shift with a spectrometer or detector array. Additionally, these high-resolution sensors employ multiple
resonance peaks at identical physical location on the sensor surface. Each of these resonance peaks responds uniquely to
the detection event, thereby enriching the data set available for quantification. The peaks result from individual,
polarization-dependent resonant leaky modes that are the foundation of this technology. Examples are presented for
detection of ovarian cancer biomarkers (fibronectin and apoliprotein A-1) in serum and cell culture supernatant, with
detection sensitivities to ~20 ng/ml. Minimal nonspecific binding was measured in cell media and serum backgrounds.
We also present an example dual-polarization resonance response with corresponding backfitting results that illustrate
the capability to distinguish between changes at the sensor surface due to biolayer adhesion and those due to sample
A high-accuracy sensor system has been developed that provides near-instantaneous detection of biomarker proteins as
indicators of ovarian serous papillary carcinoma. Based upon photonic guided-mode resonance technology, these highresolution
sensors employ multiple resonance peaks to rapidly test for relevant proteins in complex biological samples.
This label-free sensor approach requires minimal sample processing and has the capability to measure multiple agents
simultaneously and in real time. A detection system has been developed and performance characterized. Identification
and quantification of protein biomarkers that are up- or downregulated in blood and serum as indicators of ovarian
cancer will be presented.
Resonant leaky modes can be induced on dielectric, semiconductor, and metallic periodic layers patterned in one or two
dimensions. Potential applications include bandpass and bandstop filters, laser mirrors, ultrasensitive biosensors,
absorption enhancement in solar cells, security devices, tunable filters, nanoelectromechanical display pixels,
dispersion/slow-light elements, and others. As there is now a growing realization worldwide of the utility of these
devices, it is of interest to summarize their physical basis and present their applicability in photonic devices and systems.
In particular, we have invented and implemented highly accurate, label-free, guided-mode resonance (GMR) biosensors
that are being commercialized. The sensor is based on the high parametric sensitivity inherent in the fundamental
resonance effect. As an attaching biomolecular layer changes the parameters of the resonance element, the resonance
frequency (wavelength) changes. A target analyte interacting with a bio-selective layer on the sensor can thus be
identified without additional processing or use of foreign tags. Another promising pursuit in this field is development of
optical components including wideband mirrors, filters, and polarizers. We have experimentally realized such devices
that exhibit a minimal layer count relative to their classical multilayer thin-film counterparts. Theoretical modeling has
shown that wideband tuning of these filters is achievable by perturbing the structural symmetry using
nano/microelectromechanical (MEMS) methods. MEMS-tuned resonance elements may be useful as pixels in spatial
light modulators, tunable lasers, and multispectral imaging applications. Finally, mixed metallic/dielectric resonance
elements exhibit simultaneous plasmonic and leaky-mode resonance effects. Their design and chief characteristics is
A new tag-free photonic resonance concept occurring on subwavelength waveguide gratings is applied for rapid
medical testing applications. These high-resolution sensors operate in real time while being sensitive to a wide variety of
analytes, including microbials. This method does not require extensive processing steps, thus simplifying assay tests and
enabling a rapid response (less than 30 minutes is possible). In this work, a sensor system that uses a single, fixed-wavelength
source with a shaped input wavefront to auto-scan in angle has been developed. As binding events occur at
the sensor surface, shifts in a resonance reflection peak (or a corresponding transmission minimum) are tracked as a
function of incident angle. The amount of angular shift is correlated to the quantity of analyte in the test sample. Due to
inherent polarization diversity, two narrow peaks shift their positions on the sensor surface when a bioreaction occurs,
thereby providing cross-referenced data. The sensor system connects to portable interfaces for data acquisition and
analysis by dedicated software codes. A portable guided-mode resonance sensor system prototype has been developed.
Its performance for the detection of the microbial <i>S. aureus </i>in buffer and rat serum is presented in this paper.
This paper presents key properties and examples of applications of resonant leaky-mode biosensors operating in the subwavelength regime. The main resonance features observed under variation of input wavelength and angle are discussed. The dependence of the resonance lineshape on element design parameters is highlighted. The surface-localized power concentration at resonance is described along with the standing-wave pattern of the leaky modes obtained at normal incidence. An example fabrication process involving holographic patterning, etching, and deposition of high-index material is provided. The fabricated elements resonate well with good agreement between experiment and theory found. As examples of practical applications, experimental results on detection of proteins and bacteria are given. The tag-free resonant sensor technology demonstrated may be feasible for use in fields such as in medical diagnostics, drug development, environmental monitoring, and homeland security.
Optical sensor technology based on subwavelength periodic waveguides is applied for tag-free, high-resolution biomedical and chemical detection. Measured resonance wavelength shifts of 6.4 nm for chemically attached Bovine Serum Albumin agree well with theory for a sensor tested in air. Reflection peak efficiencies of 90% are measured, and do not degrade upon biolayer attachment. Phase detection methods are investigated to enhance sensor sensitivity and resolution. Direct measurement of the resonant phase response is reported for the first time using ellipsometric measurement techniques.
A new fiber optic sensor integrating dielectric diffraction gratings and thin films on optical fiber endfaces is prosed for biomedical sensing applications. This device utilizes a resonant dielectric waveguide grating structure fabricated on an optical fiber endface to probe reactions occurring in a sensing layer deposited on its surface. The operation of this sensor is based upon a fundamental resonance effect that occurs in waveguide gratings. An incident broad- spectrum signal is guided within an optical fiber and is filtered to reflect or transmit a desired spectral band by the diffractive thin film structure on its endface. Slight changes in one or more parameters of the waveguide grating, such as refractive index or thickness, can result in a responsive shift of the reflected or transmitted spectral peak that can be detected with spectroscopic instruments. This new sensor concept combines improved sensitivity and accuracy with attractive features found separately in currently available fiber optic sensors, such as large dynamic range, small sensing proximity, real time operation, and remote sensing. Diffractive elements of this type consisting of a photoresist grating on a Si<SUB>3</SUB>N<SUB>4</SUB> waveguide have been fabricated on multimode optical fiber endfaces with 100 micrometers cores. Preliminary experimental tests using a tunable Ti:sapphire laser indicate notches of 18 percent in the transmission spectrum of the fiber endface guided-mode resonance devices. A theoretical analysis of the device performance capabilities is presented and applied to evaluate the feasibility and potential advantages of this bioprobe.
High-efficiency resonance coupling effects in zero-order diffractive multilayer structures have applications in fields such as optical filtering and laser technology. These resonance effects arise on phase matching of an incident laser beam to a leaky waveguide mode. Then, in theory, complete energy exchange between the input wave and a reflected wave can take place within narrow ranges in wavelength, angle of incidence, index of refraction, or layer thickness. This paper addresses theoretical modeling, experimental realization, and applications of this so-called guided-mode resonance (GMR) effect. In particular, the achievable GMR-filter efficiencies, spectral linewidths, sideband levels, and polarization characteristics are treated with a plane-wave model and a Gaussian-beam model. Resonance bandpass filters operating in reflection and transmission are shown to exhibit high efficiencies and extended low sidebands. Genetic algorithms are applied to solve inverse resonance-filter design problems. Applications including GMR laser mirrors, electro-optic modulators, and resonant Brewster filters are presented. Experimental results are shown to agree well with theoretical calculations.
To obtain uniform illumination of photonic reconfigurable antennas, a waveguide grating with a nonuniform grating profile may be used. Theoretical studies using approximate models indicate that the grating profile should have a hyperbolic spatial variation along the length of the coupler. This yields a spatially varying diffraction efficiency that compensates for the loss of light as it is diffracted out of the waveguide. Utilizing a holographic interferometer with a computer controlled shutter in one arm, gratings with appropriate spatial profile variation have been recorded in photoresist and transferred to produce photopolymer waveguide gratings. These planar couplers are integrated with optical fiber bundles for input light delivery. The grating periods are chosen to produce orthogonally propagating output waves. A dielectric mirror arrangement is used to reflect the parasitic diffracted order back onto the antenna element. The best devices obtained to date exhibit output uniformity of plus or minus 6% over a coupler length of 20 mm with total efficiency exceeding 50%.