Scholarly Works, Center for Photonics Technology

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Research articles, presentations, and other scholarship

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Powder-in-Tube Reactive Molten-Core Fabrication of Glass-Clad BaO-TiO2-SiO2 Glass–Ceramic Fibers
Yang, Shuo; Heyl, Hanna; Homa, Daniel S.; Pickrell, Gary R.; Wang, Anbo (MDPI, 2020-01-15)
In this paper we report the fabrication of glass-clad BaO-TiO₂-SiO₂ (BTS) glass–ceramic fibers by powder-in-tube reactive molten-core drawing and successive isothermal heat treatment. Upon drawing, the inserted raw powder materials in the fused silica tubing melt and react with the fused silica tubing (housing tubing) via dissolution and diffusion interactions. During the drawing process, the fused silica tubing not only serves as a reactive crucible, but also as a fiber cladding layer. The formation of the BTS glass–ceramic structure in the core was verified by micro-Raman spectroscopy after the successive isothermal heat treatment. Second-harmonic generation and blue-white photoluminescence were observed in the fiber using 1064 nm and 266 nm picosecond laser irradiation, respectively. Therefore, the BTS glass–ceramic fiber is a promising candidate for all fiber based second-order nonlinear and photoluminescence applications. Moreover, the powder-in-tube reactive molten core method offers a more efficient and intrinsic contamination-free approach to fabricate glass–ceramic fibers.
Dissolution and Diffusion-Based Reactions within YBa2Cu3O7-x Glass Fibers
Heyl, Hanna; Yang, Shuo; Homa, Daniel S.; Slebodnick, Carla; Wang, Anbo; Pickrell, Gary R. (MDPI, 2019-12-20)
This work presents a thorough identification and analysis of the dissolution and diffusion-based reaction processes that occur during the drawing of YBa₂Cu₃O_7-x (YBCO) glass-clad fibers, using the molten-core approach, on a fiber draw tower in vacuum and in oxygen atmospheres. The results identify the dissolution of the fused silica cladding and the subsequent diffusion of silicon and oxygen into the molten YBCO core. This leads to a phase separation due to a miscibility gap which occurs in the YBCO–SiO₂ system. Due to this phase separation, silica-rich precipitations form upon quenching. XRD analyses reveal that the core of the vacuum as-drawn YBCO fiber is amorphous. Heat-treatments of the vacuum as-drawn fibers in the 800–1200 °C range show that cuprite crystallizes out of the amorphous matrix by 800 °C, followed by cristobalite by 900 °C. Heat-treatments at 1100 °C and 1200 °C lead to the formation of barium copper and yttrium barium silicates. These results provide a fundamental understanding of phase relations in the YBCO–SiO₂ glass-clad system as well as indispensable insights covering general glass-clad fibers drawn using the molten-core approach.
Coupled Mode Analysis for 3D Stress-Free Elastic Acoustic Waveguide
He, Jiaji; Homa, Daniel S.; Pickrell, Gary R.; Wang, Anbo (IEEE, 2019)
Acoustic sensors and acoustic measurements receive much attention in various applications. Because waveguides are commonly used in sensor design, theoretical means to study acoustic propagation and interaction in waveguides are necessary. However, current methods for elastic wave coupling, including the transfer matrix method and coupled mode theory in planar 2D waveguides, are not satisfactory. In this work, a coupled mode analysis for acoustic waves in 3D stress-free elastic waveguides is proposed. Similar to the coupled mode theory in optical waveguides, the analysis is presented by the evolution of modal amplitudes. It can solve various modal conversion and scattering problems in elastic waveguides with small changes of cross sections and stress-free boundaries. To demonstrate the practicability, the coupled mode analysis is used to calculate the reflection spectrum of the newly proposed structure, the acoustic fiber Bragg grating. In a notch-based grating fabricated on a thin cylindrical waveguide, the results from coupled mode analysis are in good agreement with those from the transfer matrix method, which has been already validated experimentally. The coupled mode analysis is a promising method to solve various scattering problems.
Photonic Biosensor Assays to Detect and Distinguish Subspecies of Francisella tularensis
Cooper, Kristie L.; Bandara, Aloka B.; Wang, Yunmiao; Wang, Anbo; Inzana, Thomas J. (MDPI, 2011-03-07)
The application of photonic biosensor assays to diagnose the category-A select agent Francisella tularensis was investigated. Both interferometric and long period fiber grating sensing structures were successfully demonstrated; both these sensors are capable of detecting the optical changes induced by either immunological binding or DNA hybridization. Detection was made possible by the attachment of DNA probes or immunoglobulins (IgG) directly to the fiber surface via layer-by-layer electrostatic self-assembly. An optical fiber biosensor was tested using a standard transmission mode long period fiber grating of length 15 mm and period 260 µm, and coated with the IgG fraction of antiserum to F. tularensis. The IgG was deposited onto the optical fiber surface in a nanostructured film, and the resulting refractive index change was measured using spectroscopic ellipsometry. The presence of F. tularensis was detected from the decrease of peak wavelength caused by binding of specific antigen. Detection and differentiation of F. tularensis subspecies tularensis (type A strain TI0902) and subspecies holarctica (type B strain LVS) was further accomplished using a single-mode multi-cavity fiber Fabry-Perot interferometric sensor. These sensors were prepared by depositing seven polymer bilayers onto the fiber tip followed by attaching one of two DNA probes: (a) a 101-bp probe from the yhhW gene unique to type-A strains, or (b) a 117-bp probe of the lpnA gene, common to both type-A and type-B strains. The yhhW probe was reactive with the type-A, but not the type-B strain. Probe lpnA was reactive with both type-A and type-B strains. Nanogram quantities of the target DNA could be detected, highlighting the sensitivity of this method for DNA detection without the use of PCR. The DNA probe reacted with 100% homologous target DNA, but did not react with sequences containing 2-bp mismatches, indicating the high specificity of the assay. These assays will fill an important void that exists for rapid, culture-free, and field-compatible diagnosis of F. tularensis.
Long Period Gratings in Random Hole Optical Fibers for Refractive Index Sensing
Wang, Ke; Pickrell, Gary R. (MDPI, 2011-02-01)
We have demonstrated the fabrication of long period gratings in random hole optical fibers. The long period gratings are fabricated by a point-by-point technique using a CO2 laser. The gratings with a periodicity of 450 µm are fabricated and a maximum coupling efficiency of −9.81 dB has been achieved. Sensing of different refractive indices in the surrounding mediums is demonstrated by applying standard liquids with refractive indices from 1.400 to 1.440 to the long period grating.
Quantitative phase spectroscopy
Rinehart, M.; Zhu, Y.; Wax, A. (2012-05-01)
Quantitative phase spectroscopy is presented as a novel method of measuring the wavelength-dependent refractive index of microscopic volumes. Light from a broadband source is filtered to an ~5 nm bandwidth and rapidly tuned across the visible spectrum in 1 nm increments by an acousto-optic tunable filter (AOTF). Quantitative phase images of semitransparent samples are recovered at each wavelength using off-axis interferometry and are processed to recover relative and absolute dispersion measurements. We demonstrate the utility of this approach by (i) spectrally averaging phase images to reduce coherent noise, (ii) measuring absorptive and dispersive features in microspheres, and (iii) quantifying bulk hemoglobin concentrations by absolute refractive index measurements. Considerations of using low coherence illumination and the extension of spectral techniques in quantitative phase measurements are discussed.
ZrO2 Thin-Film-Based Sapphire Fiber Temperature Sensor
Wang, Jiajun; Lally, Evan M.; Wang, Xiaoping; Gong, Jianmin; Pickrell, Gary R.; Wang, Anbo (Optical Society of America, 2012-10-01)
A submicrometer-thick zirconium dioxide film was deposited on the tip of a polished C-plane sapphire fiber to fabricate a temperature sensor that can work to an extended temperature range. Zirconium dioxide was selected as the thin film material to fabricate the temperature sensor because it has relatively close thermal expansion to that of sapphire, but more importantly it does not react appreciably with sapphire up to 1800 degrees C. In order to study the properties of the deposited thin film, ZrO2 was also deposited on C-plane sapphire substrates and characterized by x-ray diffraction for phase analysis as well as by atomic force microscopy for analysis of surface morphology. Using low-coherence optical interferometry, the fabricated thin-film-based sapphire fiber sensor was tested in the lab up to 1200 C and calibrated from 200 degrees to 1000 degrees C. The temperature resolution is determined to be 5.8 degrees C when using an Ocean Optics USB4000 spectrometer to detect the reflection spectra from the ZrO2 thin-film temperature sensor. (C) 2012 Optical Society of America OCIS codes: 060.2370, 120.6780, 310.1620.
Signal Processing Of White-Light Interferometric Low-Finesse Fiber-Optic Fabry-Perot Sensors
Ma, Cheng; Wang, Anbo (Optical Society of America, 2013-08-01)
Signal processing for low-finesse fiber-optic Fabry-Perot sensors based on white-light interferometry is investigated. The problem is demonstrated as analogous to the parameter estimation of a noisy, real, discrete harmonic of finite length. The Cramer-Rao bounds for the estimators are given, and three algorithms are evaluated and proven to approach the bounds. A long-standing problem with these types of sensors is the unpredictable jumps in the phase estimation. Emphasis is made on the property and mechanism of the "total phase" estimator in reducing the estimation error, and a varying phase term in the total phase is identified to be responsible for the unwanted demodulation jumps. The theories are verified by simulation and experiment. A solution to reducing the probability of jump is demonstrated. (C) 2013 Optical Society of America
Surface-Mount Sapphire Interferometric Temperature Sensor
Zhu, Y. Z.; Wang, Anbo (Optical Society of America, 2006-02-01)
A fiber-optic high-temperature sensor is demonstrated by bonding a 45 degrees-polished single-crystal sapphire fiber on the surface of a sapphire wafer, whose optical thickness is temperature dependent and measured by white-light interferometry. A novel adhesive-free coupling between the silica and sapphire fibers is achieved by fusion splicing, and its performance is characterized. The sensor's interference signal is investigated for its dependence on angular alignment between the fiber and the wafer. A prototype sensor is tested to 1170 degrees C with a resolution of 0.4 degrees C, demonstrating excellent potential for high-temperature measurement. (C) 2006 Optical. Society of America.
Self-Compensating Fiber Optic Flow Sensor System And Its Field Applications
Peng, W.; Pickrell, Gary R.; Huang, Z. Y.; Xu, J. C.; Kim, D. W.; Qi, B.; Wang, Anbo (Optical Society of America, 2004-07-01)
A self-compensating fiber optic flow sensor system based on the principle of broadband white-light interferometers and cantilever beam bending is described. The fiber optic sensor system uses two fiber ferrule sensors that are bonded on either side of a cantilever beam to measure the flow rate by monitoring the air-gap changes caused by the bending of the cantilever beam. Cross sensitivity of the temperature and pressure dependence of the sensor can be compensated for automatically. The prototype sensor system was constructed, laboratory characterized, and field tested. The results from the field testing have demonstrated high resolution, repeatability, and stability for on-line detection of the flow rates of fluids. (C) 2004 Optical Society of America.
Optical Scanning Cryptography For Secure Wireless Transmission
Poon, Ting-Chung; Kim, Taegeun; Doh, K. (Optical Society of America, 2003-09-01)
We propose a method for secure wireless transmission of encrypted information. By use of an encryption key, an image or document is optically encrypted by optical heterodyne scanning and hence encryption is performed on the fly. We call this technique optical scanning cryptography. The output of the heterodyne encrypted signal is at radio frequency and can be directly sent through an antenna to a secure site for digital storage to be prepared for decryption. In the secure site, an identical optical scanning system to that used for encryption is used, together with a decryption key, to generate an electrical signal. The electrical signal is then processed and sent to a computer to be used for decryption. Utilizing the stored information received from the encryption stage and the electrical information from the secure site, a digital decryption unit performs a decryption algorithm. If the encryption key and the decryption key are matched, the decryption unit will decrypt the image or document faithfully. The overall cryptosystem can perform the incoherent optical processing counterpart of the well-known coherent double-random phase-encoding technique. We present computer simulations of the idea. (C) 2003 Optical Society of America.
Observation Of The Enhanced Backscattering Of Light By The End Of A Tilted Dielectric Cylinder Owing To The Caustic Merging Transition
Marston, Philip L.; Zhang, Yibing; Thiessen, David B. (Optical Society of America, 2003-03-01)
The scattering of light by obliquely illuminated circular dielectric cylinders was previously demonstrated to be enhanced by a merger of Airy caustics at a critical tilt angle. [Appl. Opt. 37, 1534 (1998)]. A related enhancement is demonstrated here for backward and near-backward scattering for cylinders cut with a flat end perpendicular to the cylinder's axis. It is expected that merged caustics will enhance the backscattering by clouds of randomly oriented circular cylinders that have appropriately flat ends. (C) 2003 Optical Society of America.
Optical Image Recognition Of Three-Dimensional Objects
Poon, Ting-Chung; Kim, Taegeun (Optical Society of America, 1999-09-01)
A three-dimensional (3-D) optical image-recognition technique is proposed and studied. The proposed technique is based on two-pupil optical heterodyne scanning and is capable of performing 3-D image recognition. A hologram of the 3-D reference object is first created and then is used to modulate spatially one of the pupils of the optical system; the other pupil is a point source. A 3-D target object to be recognized is then scanned in two dimensions by optical beams modulated by the two pupils. The result of the two-dimensional scan pattern effectively displays the correlation of the holographic information of the 3-D reference object and that of the 3-D target object. A strong correlation peak results if the two pieces of the holographic information are matched. We analyze the proposed technique and thereby lay a theoretical foundation for optical implementations of the idea. Finally, computer simulations are performed to verify the proposed idea. (C) 1999 Optical Society of America.
Multimode Excitation-Induced Phase Shifts in Intrinsic Fabry-Perot Interferometric Fiber Sensor Spectra
Ma, Cheng; Wang, Anbo (Optical Society of America, 2010-11-01)
We report the modal analysis of optical fiber single-mode-multimode-single-mode intrinsic Fabry-Perot interferometer sensors. The multimode nature of the Fabry-Perot cavity gives rise to an additional phase term in the spectrogram due to intermodal dispersion-induced wavefront distortion, which could significantly affect the cavity length demodulation accuracy. By using an exact model to analyze the modal behavior, this phase term is explained by employing a rotating vector approach. Comparison of the theoretical analysis with experimental results is presented. (c) 2010 Optical Society of America
Micro-Air-Gap Based Intrinsic Fabry-Perot Interferometric Fiber-Optic Sensor
Chen, X. P.; Shen, F. B.; Wang, Z. A.; Huang, Z. Y.; Wang, Anbo (Optical Society of America, 2006-05-01)
A simple intrinsic Fabry-Perot interferometric (IFPI) sensor is developed. The sensor is fabricated by two micro air gaps as reflective mirrors in a fiber to form a Fabry-Perot cavity. Theoretical and experimental studies of the sensor are described. Experimental results show that high resolution and high sensitivity can be achieved. Two structures of micro-air-gap-based IFPI sensors offer more applications than other IFPI sensors. (c) 2006 Optical Society of America.
Manufacturing Of A Fiber Optic Young's Double Pinhole Interferometer For Use As A 3D Profilometer
Pennington, Timothy L.; Wang, Anbo; Xaio, Hai; May, Russell G. (Optical Society of America, 2000-05-01)
The method used to manufature a Young's double pinhole interferometer is discussed. This interferometer is destined to be used in a surface profilometer using two wavelengths so that the zero order fringe can be determined. Hence stringent requirements are placed on the absolute length difference between the two output fibers of a single mode coupler. These requirements are discussed along with the manufacturing process. The interferometer is shown along with measurements showing a length difference on the order of 6 mu m. (C) 2000 Optical Society of America.
Method Of Multiple References For 3D Imaging with Fourier Transform Interferometry
Lally, Evan M.; Gong, Jianmin; Wang, Anbo (Optical Society of America, 2010-03-01)
This letter presents an improved phase referencing technique, called Method of Multiple References, for optical profilometry. Based on a lookup table, the method eliminates several major drawbacks of single-reference Fourier Transform Interferometry by enabling surface error correction for steep slopes and step discontinuities, and by allowing mapping of multiple discrete objects using a single image set. The algorithm is tested using a fiber optic coupler-based FTI system and shown to have RMS surface error less than 0.03mm. (C) 2010 Optical Society of America
In-Fiber Reflection Mode Interferometer Based on A Long-Period Grating For External Refractive-Index Measurement
Kim, D. W.; Zhang, Y.; Cooper, K. L.; Wang, Anbo (Optical Society of America, 2005-04-01)
We present two novel schemes for refractometry based on a long-period fiber grating- (LPG-) based Michelson interferometer. These schemes are designed to overcome the measurement dependence of previously demonstrated LPG-based refractometry on the immersion depth. The first utilizes an unshielded LPG and the second, a shielded one. Both schemes were tested over a certain refractive-index range, and the measurement of glucose concentration in water was experimentally demonstrated. In addition, the temperature sensitivity of the two schemes is discussed. (c) 2005 Optical Society of America.
Implementation Of A Loss-Compensated Recirculating Delayed Self-Heterodyne Interferometer For Ultranarrow Laser Linewidth Measurement
Chen, X. P.; Han, M.; Zhu, Y. Z.; Dong, Bin; Wang, Anbo (Optical Society of America, 2006-12-01)
Ultranarrow laser linewidth measurement using an optimized loss-compensated recirculating delayed self-heterodyne interferometer is described. An experimental setup is constructed to measure subkilohertz laser linewidths. The system parameters are optimized to obtain the best beat signals. The experimental results agree well with the theoretical analysis. Two methods of linewidth interpretation are presented and analyzed based on the experimental results. It is proved that a loss-compensated recirculating delayed self-heterodyne interferometer is an effective tool for measuring an ultranarrow laser linewidth. (c) 2006 Optical Society of America.
Frequency-Estimation-Based Signal-Processing Algorithm For White-Light Optical Fiber Fabry-Perot Interferometers
Shen, F. B.; Wang, Anbo (Optical Society of America, 2005)
A novel signal-processing algorithm based on frequency estimation of the spectrogram of single-mode optical fiber Fabry-Perot interferometric sensors under white-light illumination is described. The frequency-estimation approach is based on linear regression of the instantaneous phase of an analytical signal, which can be obtained by preprocessing the original spectrogram with a bandpass filter. This method can be used for a relatively large cavity length without the need for spectrogram normalization to the spectrum of the light source and can be extended directly to a multiplexed sensor system. Experimental results show that the method can yield both absolute measurement with high resolution and a large dynamic range. Performance analysis shows that the method is tolerant of background noise and variations of the source spectrum. (c) 2005 Optical Society of America.

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