This PDF file contains the front matter associated with SPIE Proceedings Volume 7322, including the Title Page, Copyright information, Table of Contents, and the Conference Committee listing.

Fiber inline core-cladding-mode interferometers (CCMI) fabricated by CO₂ laser irradiations were demonstrated. CCMI sensors operate based on the interference between the core mode and the cladding modes. Based on the way the interferometer is configured, CCMI sensors can be categorized into two groups, namely the Mach-Zehnder interferometer (MZI) type and the Michelson interferometer (MI) type. The MZI sensor works in transmission mode, i.e., the transmitted interference signal is detected. The MI sensor works in reflection mode, where the light passes the interferometer twice and the reflected interference signal is detected. We conducted a temperature test and a refractive index test to demonstrate their sensing capability.

Breast cancer is the most frequently diagnosed malignancy in women worldwide. Because of its great impact on society, a lot of research funding has been used to develop novel detection tools for aiding breast cancer diagnosis and prognosis. In this work, we demonstrated a simple, fast, and sensitive detection of circulating breast cancer biomarker CA15-3 with opto-fluidic ring resonator (OFRR) sensors. The OFRR sensor employs a thin-walled capillary with wall thickness less than 4 μm. The circular cross section of the capillary forms the optical ring resonator, in which the light circulates in the form of whispering gallery modes (WGMs). The capillary wall is thin enough that the evanescent field of the WGM extends into the capillary core and responds to refractive index changes in the capillary core or close to its interior surface. The WGM spectral position will change when the biomolecules bind to the surface, yielding quantitative and kinetic information about the biomolecule interaction. Here, the direct immunoassay method was employed for the detection of CA15-3 antigen without any signal amplification steps. The sensor performance in both PBS buffer and human serum were investigated, respectively. The experimental detection limit was 5 units/mL in PBS buffer and 30 units/mL for CA15-3 spiked in serum, both of which satisfied clinical diagnosis requirements. The potential use of the OFRR as the point-of-care device for breast cancer detection was tested by measuring the CA15-3 level in blood samples collected from stage IV breast cancer patients and the results were compared with standard clinical test.

In this work, we theoretically and experimentally demonstrate a highly sensitive porous silicon membrane waveguide biosensor in the Kretschmann configuration, and show how the cladding material directly impacts the waveguide sensor detection sensitivity and resonance width. Dielectric and metal-clad porous waveguides in the Kretchmann configuration have the potential to achieve significantly enhanced performance for small molecule detection compared to planar waveguide and surface plasmon resonance sensors due to increased surface area and strong field confinement in the porous waveguide layer. First order perturbation theory calculations predict that the quality factors of polymer-cladded porous silicon waveguides with porous silicon losses less than ~500 dB/cm are at least two times larger than the quality factors of gold-cladded porous silicon waveguides and traditional surface plasmon resonance sensors.

Metallic nanohole arrays support surface electromagnetic waves that enable enhanced optical transmission and may be exploited for sensing. Our group has been active in the application of enhanced optical transmission to chemical and biological sensing, and in the optofluidic integration nanohole arrays. Recent work in this area is described here. Recent work using a blocking layer to limit the exposed metal surface to the in-hole region resulted in effective sensing in a much smaller, nanoconfined volume. This result motivates the use of through nanoholes, (i.e. nanoholes as nanochannels) to directly address the sensing area. A flow-through nanohole array based sensing format is presented that leads to enhanced transport of reactants to the active area and a solution sieving action that is unique among surfacebased sensing methods. The pertinent fluid and solid mechanics aspects of the flow-through nanohole array sensing are discussed and recent flow-through sensing results are presented. The application of dielectrophoresis to influence particle transport in flow-through nanohole arrays is also discussed. Specifically, simulations indicate that equivalent dielectrophoretic forces are compatible with drag forces for flow rates in the range already defined in the context of biomarker transport and membrane strength considerations. Importantly, these results indicate that dielectrophoretic trapping is viable in these systems. The confinement of particles in the nanoholes opens opportunities for analyte concentration and surface enhanced Raman scattering in flow-through nanohole array based fluidic systems.

We demonstrate the utility of the opto-fluidic ring resonator (OFRR) sensor for the purpose of analyzing the degree of methylation in sample oligonucleotides. Cytosine methylation, a regular epigenetic function in cellular growth and metabolism, is prone to abnormal behavior that may lead to uncontrolled suppression of key genes involved with cellular proliferation. Such behavior is suspected to be strongly related to the occurrence of several types of cancers. The OFRR is demonstrated as a tool to explore and monitor the degree of methylation in DNA. Two different approaches are explored, using either bisulfite modification or immunoprecipitation. The methods are compared and the signal response for both methods is characterized.

We demonstrate an alternative to total internal reflection fluorescence (TIRF) microscopy. A method for imaging ultra thin films and living cells located on waveguides illuminated with their evanescent fields is introduced. Analysis of ion-exchanged waveguides focusing on their application as substrates for microscopic study of interfacial phenomena is presented. Various LB film stacks were imaged to verify the intensity interpretation due to the exponentially decaying evanescent fields of the waveguides. The paper gives an overview on the imaging applications of this technique. The fluorescence intensity has been used to determine quantitatively the cell attachment of osteoblasts (bone forming cells) to substrate surfaces. In live cell studies trypsin (a protease) was used to alter attachment of the cells to the substrate, as a means to demonstrate feasibility of the method in measuring attachment dynamics of cells in real time.

In this work we have designed, fabricated, and tested a photonic crystal slab (PCS) with a line defect waveguide for the detection and identification of pathogenic DNA. A PCS is constructed by fabricating a material with 2-dimensional dielectric periodicity sandwiched between two semi-infinite cladding regions of lower effective index [1]. In order to uniquely identify pathogens critical to medical and homeland defense applications, the PCS was functionalized with a single stranded probe molecule providing highly specific binding for the target DNA. Integrated microfluidic channels provide delivery of the pathogen DNA resulting in hybridization and binding in the PCS holes. The binding event changes the refractive index of the PCS which results in a measurable change in the transmitted power. We will discuss design parameters and the suite of modeling tools used to optimize the PCS, defect waveguide, and coupling devices. An overview of the fabrication methods and tools will be provided and we will also report preliminary experimental results.

Dense nanocrystalline copper-doped zirconia (CDZ, Cu:Zr=16:84) thin film was coated on the surface of a 125 μm-diameter long-period fiber grating (LPFG) by a facile synthesis route involving polymeric precursor coating and subsequent thermal treatments. The CDZ film had a uniform thickness of ~100 nm and grain size of 20 to 35 nm after a brief annealing step at 700°C for 1 hour. This CDZ thin film coated LPFG (CDZ-LPFG) was evaluated at a high temperature of 550°C for its change of resonant wavelength (λ_R) in response to the variation of carbon monoxide (CO) concentration in nitrogen (N₂). The λ_R was found to shift toward longer wavelength when increasing the CO concentration. The CDZ-LPFG sensor response was found to be reproducible and reversible at low level CO concentrations (<1,000 ppm) but became irreversible when the CO concentration was high (e.g. at 10,000 ppm). The high temperature stability of the CDZ material in CO-containing atmospheres was studied to understand the limit of CO measurement range.

We have demonstrated the use of the Opto-Fluidic ring resonator (OFRR) to achieve the label-free detection of CD4+ and CD8+ T-Lymphocytes. The OFRR sensing technology combines microfluidics and optical sensing in a small platform that achieves rapid detection. In this work, white blood cells were obtained from healthy blood and the concentration altered to reflect CD4 and CD8 concentrations of HIV infected individuals. The OFRR was modified to effectively capture these receptors located on T-Lymphocytes and obtain a sensing signal through interaction with an evanescent field. Results show isolation of CD4+ and CD8+ T-Lymphocytes at medically significant levels. This work will lead to a device that can provide a CD4 and CD8 count to measure HIV progression in a low cost sensing setup.

We develop a novel chemical vapor sensing platform based on optofluidic ring resonator (OFRR) for rapid and on-column detection and analysis of a wide range of chemical vapors. The OFRR is a thin-walled fused-silica capillary with a diameter of ~100 μm and a few centimeters in length. The circular cross-section of the OFRR defines a ring resonator that supports high-Q (>10⁶) whispering gallery modes or circulating waveguide modes (WGMs). Polymer thin film is coated on the OFRR capillary interior surface as a vapor sensitive material. The unique structure of the OFRR achieves dual-use of the capillary as the gas delivery channel and as the sensing transducer, avoiding the necessity of building extra gas detection chambers commonly seen in chemical vapor sensors. When vapor molecules pass through the OFRR, the interaction between vapor molecules and the polymer causes polymer refractive index and thickness to change, which leads to a WGM spectral shift. Therefore, by monitoring the WGMs spectrum in time, the quantitative and kinetic information regarding vapor molecule-polymer interaction is acquired. The rapid detection of methanol and hexane vapors representing polar and nonpolar analytes respectively are demonstrated with OFRR vapor sensors. Owing to the unique multipoint on-column detection capability, the OFRR vapor sensor is studied for the development of the micro- GC gas analyzer. Efficient separation and rapid detection are achieved by a few centimeters long OFRR capillary coated with a stationary phase polymer. We further explore the capability of OFRR micro-GC for more challenging explosive detection. The OFRR vapor sensing platform is a promising candidate for the development of rapid, sensitive, simple, portable, and cost-effective micro-gas sensors.

This paper demonstrates the chemical sensing capability of a miniaturized fiber inline Fabry-Pérot sensor fabricated by femtosecond laser. Its accessible cavity enables the device to measure the refractive index within the cavity. The refractive index change introduced by changing the acetone solution concentration was experimentally detected with an error less than 4.2×10^-5.

There is a range of ways to couple light in a single mode fiber (SMF) from core mode to cladding modes, which can be applied in some fiber sensors. Recently, a very simple method using CO₂ laser irradiation is put forward. By coupling core mode to cladding mode in the first irritation point and re-coupling in the second one, in-line Mach-Zehnder interferometer (MFI) and Michelson interferometer(MI) sensors have be demonstrated. To understand the mechanism underneath this coupling phenomenon, several parameters (laser power, laser lasting time, etc) tests are investigated. With bigger laser power and longer lasting time, one can obtain higher mode coupling, which is potential for greater sensitivity sensor. Combined with a long period fiber grating (LPFG), the cladding modes promoted in fiber cladding are studied. In some big power conditions, permanent deformation can be met on the irradiation points of the fiber. Although higher loss is induced, there is also other advantage, such like high temperature stability. The sensitivity and stability of temperature are discussed based on these sensors' configuration and mechanism. The experiences verify our laser irritation sensors can survive in very high temperature. When coating with some gas absorption film such like zeolite film, one reliable high sensitivity gas sensor is successfully demonstrated in low ppm vapor level.

We present novel fiber optics low coherence interferometer apparatus, and novel probe for in-situ characterization of semiconductor structures for IR detector manufacturing. Probe does not exhibit polarization, or strain sensitivity observed in earlier invented systems. In addition it is demonstrated to be able to operate with varying length of optical fibers.

We are in the process of developing an all optically driven, deformable mirror device through the integration of an array of photodetectors with an array of MEMS deformable mirror devices. In this paper we demonstrate the optical actuation of a single-pixel, deformable-mirror MEMS device through a direct cascade with a photodetector. Deformation is quasilinear at low light intensities, and saturates at higher intensities. We also describe the fabrication of an integrated device consisting of an all optically addressed deformable-mirror MEMS suspended over a p-i-n photodetector. Initial demonstration of optical actuation of the deformable mirror using the newly integrated device is also presented. We have fabricated several membrane materials, membrane structures, and photodetector arrays.

Development of localized surface plasmon resonance (LSPR) sensors for label-free biodetection draws considerable attention because of the potential of these sensors to provide simplified detection schemes, improved detection limits, and high-density multiplexed array configurations. In this paper, we present our recent results on the theoretical and experimental development of LSPR label-free biosensors based on nanohole and nanopillar arrays. First, we theoretically compare the analytical performance metrics of wavelength modulated SPR and LSPR platforms for biological recognition with surface-immobilized bioreceptors (e.g. antibodies and aptamers). Further, we discuss our results on the application of a focused ion beam (FIB) technique to fabricate arrays of nanoholes and nanopillars in Au films, investigate the origin and type of FIB-induced surface contamination, and demonstrate an efficient way for its elimination. Next, we evaluate the refractive index (RI) response sensitivity of FIB-fabricated arrays of nanoholes (443 - 513 nm/RIU) and nanopillars (423 nm/RIU) in Au films. Further, we demonstrate the opportunities that are available from the multivariate spectral analysis of plasmonic nanostructures for improvement of sensor system performance. Finally, we present typical simulation results of predicting RI sensitivity of plasmonic nanostructures using finite-difference time-domain technique (FDTD) and discuss the remaining challenges of simulation techniques for design of LSPR sensors.

Raman detection of nitrogen gas is very difficult without a multi-pass arrangement and high laser power. Hollow-core photonic bandgap fibers (HC-PBF) provide an excellent means of concentrating light energy in a very small volume and long interaction path between gas and laser. One particular commercial fiber with a core diameter of 4.9 microns offers losses of about 1dB/m for wavelengths between 510 and 610 nm. If 514nm laser is used for excitation, the entire Raman spectrum up to above 3000 cm^-1 will be contained within the transmission band of the fiber. A standard Raman microscope launches mW level 514nm laser light into the PBF and collects backscattered Raman signal exiting the fiber. The resulting spectra of nitrogen gas in air at ambient temperature and pressure exhibit a signal enhancement of about several thousand over what is attainable with the objective in air and no fiber. The design and fabrication of a flow-through cell to hold and align the fiber end allowed the instrument calibration for varying concentrations of nitrogen. The enhancement was also found to be a function of fiber length. Due to the high achieved Raman signal, rotational spectral of nitrogen and oxygen were observed in the PBF for the first time to the best of our knowledge.