Applications of Optical Fiber in Label-Free Biosensors and Bioimaging: A Review

Biosensing and bioimaging are essential in understanding biological and pathological processes in a living system, for example, in detecting and understanding certain diseases. Optical fiber has made remarkable contributions to the biosensing and bioimaging areas due to its unique advantages of compact size, immunity to electromagnetic interference, biocompatibility, fast response, etc. This review paper will present an overview of seven common types of optical fiber biosensors and optical fiber-based ultrasound detection in photoacoustic imaging (PAI) and the applications of these technologies in biosensing and bioimaging areas. Of course, there are many types of optical fiber biosensors. Still, this paper will review the most common ones: optical fiber grating, surface plasmon resonance, Sagnac interferometer, Mach–Zehnder interferometer, Michelson interferometer, Fabry–Perot Interferometer, lossy mode resonance, and surface-enhanced Raman scattering. Furthermore, different optical fiber techniques for detecting ultrasound in PAI are summarized. Finally, the main challenges and future development direction are briefly discussed.

[1]  Yong Zhao,et al.  In-fiber Optofluidic Michelson Interferometer for Detecting Small Volume and Low Concentration Chemicals with a Fiber Ring Cavity Laser , 2022, Sensors and Actuators B: Chemical.

[2]  C. Liao,et al.  Fabry-Perot Interferometer Based on a Fiber-Tip Fixed-Supported Bridge for Fast Glucose Concentration Measurement , 2022, Biosensors.

[3]  R. Bogdanowicz,et al.  Functional Fluorine-Doped Tin Oxide Coating for Opto-Electrochemical Label-Free Biosensors , 2022, SSRN Electronic Journal.

[4]  Xue-gang Li,et al.  Optical fiber SPR biosensor based on gold nanoparticle amplification for DNA hybridization detection. , 2022, Talanta.

[5]  C. Caucheteur,et al.  Relevance of the Spectral Analysis Method of Tilted Fiber Bragg Grating-Based Biosensors: A Case-Study for Heart Failure Monitoring , 2022, Sensors.

[6]  D. Tosi,et al.  Ultra-wide, attomolar-level limit detection of CD44 biomarker with a silanized optical fiber biosensor. , 2022, Biosensors & bioelectronics.

[7]  Xue-gang Li,et al.  Plug-in optical fiber SPR biosensor for lung cancer gene detection with temperature and pH compensation , 2022, Sensors and Actuators B: Chemical.

[8]  S. Linden,et al.  Achievements and perspectives of optical fiber Fabry–Perot cavities , 2021, Applied Physics B.

[9]  B. Kaushik,et al.  Localized Plasmon-Based Multicore Fiber Biosensor for Acetylcholine Detection , 2022, IEEE Transactions on Instrumentation and Measurement.

[10]  L. Nguyen,et al.  Plug-in label-free optical fiber DNA hybridization sensor based on C-type fiber Vernier effect , 2021, Sensors and Actuators B: Chemical.

[11]  F. Baldini,et al.  Nanocoated fiber label-free biosensing for perfluorooctanoic acid detection by lossy mode resonance , 2021 .

[12]  S. Campopiano,et al.  Label-free detection of vitamin D by optical biosensing based on long period fiber grating , 2021 .

[13]  Zhengyong Liu,et al.  Vernier effect assisted sucrose sensor based on cascaded Sagnac interferometer with no-core fiber , 2021, Biomedical Optics Express.

[14]  Houjin Zhang,et al.  Construction of an enzyme-based all-fiber SPR biosensor for detection of enantiomers. , 2021, Biosensors & bioelectronics.

[15]  Yong Zhao,et al.  A plug-and-play optical fiber SPR sensor for simultaneous measurement of glucose and cholesterol concentrations. , 2021, Biosensors & bioelectronics.

[16]  J. Satija,et al.  Plasmonic Fiberoptic Absorbance Biosensor (P-FAB) for Rapid Detection of SARS-CoV-2 Nucleocapsid Protein , 2021, IEEE Sensors Journal.

[17]  F. Baldini,et al.  Label-free immunosensing by long period fiber gratings at the lowest order cladding mode and near turn around point , 2021 .

[18]  Junhao Fan,et al.  Highly sensitive vibration sensor based on the dispersion turning point microfiber Mach-Zehnder interferometer. , 2021, Optics express.

[19]  F. Baldini,et al.  Analysis of the Lowest Order Cladding Mode of Long Period Fiber Gratings Near Turn Around Point , 2021, Journal of Lightwave Technology.

[20]  I. Matías,et al.  Trends in the Design of Intensity-Based Optical Fiber Biosensors (2010–2020) , 2021, Biosensors.

[21]  W. Lin,et al.  Study on a Plasmonic Tilted Fiber Grating-Based Biosensor for Calmodulin Detection , 2021, Biosensors.

[22]  Roger J. Zemp,et al.  Fiber-based photoacoustic remote sensing microscopy and spectral-domain optical coherence tomography with a dual-function 1050-nm interrogation source , 2021, Journal of biomedical optics.

[23]  L. Altucci,et al.  SARS-CoV-2 spike protein detection through a plasmonic D-shaped plastic optical fiber aptasensor , 2021, Talanta.

[24]  L. Lechuga,et al.  Label-Free Plasmonic Biosensor for Rapid, Quantitative, and Highly Sensitive COVID-19 Serology: Implementation and Clinical Validation , 2021, Analytical chemistry.

[25]  Long Jin,et al.  Fiber laser technologies for photoacoustic microscopy , 2021, Visual Computing for Industry, Biomedicine, and Art.

[26]  Jianqi Zhang,et al.  A New Type of Optical Fiber Glucose Biosensor With Enzyme Immobilized by Electrospinning , 2021, IEEE Sensors Journal.

[27]  Yong Zhao,et al.  A review of specialty fiber biosensors based on interferometer configuration , 2021, Journal of biophotonics.

[28]  Zhihai Liu,et al.  On-line SERS detection of adenine in DNA based on the optofluidic in-fiber integrated GO/PDDA/Ag NPs , 2021 .

[29]  Bo Liu,et al.  A complementary-DNA-enhanced fiber-optic sensor based on microfiber-assisted Mach-Zehnder interferometry for biocompatible pH sensing , 2021 .

[30]  Jixuan Wu,et al.  Label-Free in-Situ Detection for DNA Hybridization Employing Grapefruit-Microstructured-Optical-Fiber-Based Microfluidic Whispering Gallery Mode Resonator , 2021, IEEE Sensors Journal.

[31]  A. Yasli Cancer Detection with Surface Plasmon Resonance-Based Photonic Crystal Fiber Biosensor , 2021, Plasmonics.

[32]  D. Dolfi,et al.  Coherent Optical Fiber Sensing Based on a Frequency Shifting Loop , 2021, Journal of Lightwave Technology.

[33]  P. Shum,et al.  Dilated convolutional neural networks for fiber Bragg grating signal demodulation. , 2021, Optics express.

[34]  William A Mills,et al.  Nano-optoelectrodes Integrated with Flexible Multifunctional Fiber Probes by High-Throughput Scalable Fabrication. , 2021, ACS applied materials & interfaces.

[35]  S. S. Gorthi,et al.  Etched Fiber Bragg Grating Sensor for Quantification of DNA , 2021, IEEE Sensors Journal.

[36]  S. S. Aphale,et al.  A Surface Plasmon Resonance Bio-Sensor Based on Dual Core D-Shaped Photonic Crystal Fibre Embedded With Silver Nanowires for Multisensing , 2021, IEEE Sensors Journal.

[37]  Shobhit K. Patel,et al.  High sensitivity refractive index sensor in long-range surface plasmon resonance based on side polished optical fiber , 2021 .

[38]  Z. Ren,et al.  Highly sensitive label-free biosensor based on graphene-oxide functionalized micro-tapered long period fiber grating , 2020 .

[39]  Dachao Li,et al.  A D-shaped fiber SPR sensor with a composite nanostructure of MoS2-graphene for glucose detection. , 2020, Talanta.

[40]  A. Farmani,et al.  Systematic engineering of a nanostructure plasmonic sensing platform for ultrasensitive biomaterial detection , 2020 .

[41]  Izaddeen Kabir Yakasai,et al.  Modelling and simulation of novel liquid‐infiltrated PCF biosensor in Terahertz frequencies , 2020, IET Optoelectronics.

[42]  W. Peng,et al.  Comparative study of block copolymer-templated localized surface plasmon resonance optical fiber biosensors: CTAB or citrate-stabilized gold nanorods , 2020 .

[43]  I. Matías,et al.  Rheumatoid Arthritis miRNA biomarker detection by means of LMR based fiber-optic biosensor , 2020, 2020 IEEE Sensors.

[44]  J. Jokerst,et al.  Photoacoustic imaging with fiber optic technology: A review , 2020, Photoacoustics.

[45]  F. Baldini,et al.  Long period grating in double cladding fiber coated with graphene oxide as high-performance optical platform for biosensing , 2020, Biosensors and Bioelectronics.

[46]  B. Kaushik,et al.  Tapered Optical Fiber-Based LSPR Biosensor for Ascorbic Acid Detection , 2020, Photonic Sensors.

[47]  Md. Aslam Mollah,et al.  Detection of cancer affected cell using Sagnac interferometer based photonic crystal fiber refractive index sensor , 2020, Optical and Quantum Electronics.

[48]  L. Nguyen,et al.  All-fiber all-optical quantitative polymerase chain reaction (qPCR) , 2020, Sensors and Actuators B: Chemical.

[49]  A. Mir,et al.  A multimode graphene plasmonic perfect absorber at terahertz frequencies , 2020 .

[50]  Yong Zhao,et al.  RI sensing system with high sensitivity and large measurement range using a microfiber MZI and a photonic crystal fiber MZI , 2020 .

[51]  Santosh Kumar,et al.  Highly sensitive and selective sensor probe using glucose oxidase/gold nanoparticles/graphene oxide functionalized tapered optical fiber structure for detection of glucose , 2020 .

[52]  Qi Wang,et al.  A dual channel self-compensation optical fiber biosensor based on coupling of surface plasmon polariton , 2020 .

[53]  Seung-Woo Lee,et al.  Multi-Parameter Optical Fiber Sensing of Gaseous Ammonia and Carbon Dioxide , 2020, Journal of Lightwave Technology.

[54]  Mildred S. Cano-Velázquez,et al.  Fiber optic interferometric immunosensor based on polydimethilsiloxane (PDMS) and bioactive lipids. , 2020, Biomedical optics express.

[55]  I. Del Villar,et al.  Lossy mode resonance sensors based on nanocoated multimode-coreless-multimode fibre , 2020 .

[56]  Liyun Ding,et al.  Graphene oxide-functionalized long period fiber grating for ultrafast label-free glucose biosensor. , 2020, Materials science & engineering. C, Materials for biological applications.

[57]  Xin Wang,et al.  Tunable and switchable triple-wavelength ytterbium-doped fiber ring laser based on Sagnac interferometer with a polarization-maintaining photonic crystal fiber , 2020 .

[58]  A. Farmani,et al.  A label-free graphene-based nanosensor using surface plasmon resonance for biomaterials detection , 2020 .

[59]  R. Bogdanowicz,et al.  Simultaneous optical and electrochemical label-free biosensing with ITO-coated lossy-mode resonance sensor. , 2020, Biosensors & bioelectronics.

[60]  C. Tien,et al.  Lossy Mode Resonance Sensors Fabricated by RF Magnetron Sputtering GZO Thin Film and D-Shaped Fibers , 2020, Coatings.

[61]  Yuqian Zhao,et al.  Complete-noncontact photoacoustic microscopy by detection of initial pressures using a 3×3 coupler-based fiber-optic interferometer. , 2019, Biomedical optics express.

[62]  Yong Zhao,et al.  In-line microfiber MZI operating at two sides of the dispersion turning point for ultrasensitive RI and temperature measurement , 2020 .

[63]  Christophe Caucheteur,et al.  Functionalized etched tilted fiber Bragg grating aptasensor for label-free protein detection. , 2019, Biosensors & bioelectronics.

[64]  Brajesh Kumar Kaushik,et al.  LSPR based uric acid sensor using graphene oxide and gold nanoparticles functionalized tapered fiber , 2019 .

[65]  L. Nguyen,et al.  Multiplexed Optical Fiber Biochemical Sensing Using Cascaded C-Shaped Fabry–Perot Interferometers , 2019, IEEE Sensors Journal.

[66]  Qi Wang,et al.  Lossy mode resonance-based fiber optic sensor using layer-by-layer SnO2 thin film and SnO2 nanoparticles , 2019, Applied Surface Science.

[67]  Qi Wang,et al.  A Novel Fiber-Based Symmetrical Long-Range Surface Plasmon Resonance Biosensor With High Quality Factor and Temperature Self-Reference , 2019, IEEE Transactions on Nanotechnology.

[68]  Yong Zhao,et al.  Current status of optical fiber biosensor based on surface plasmon resonance. , 2019, Biosensors & bioelectronics.

[69]  Christophe Caucheteur,et al.  Non-enzymatic D-glucose plasmonic optical fiber grating biosensor. , 2019, Biosensors & bioelectronics.

[70]  Brajesh Kumar Kaushik,et al.  LSPR-Based Cholesterol Biosensor Using Hollow Core Fiber Structure , 2019, IEEE Sensors Journal.

[71]  A. Zarifkar,et al.  Particle swarm optimization and finite-difference time-domain (PSO/FDTD) algorithms for a surface plasmon resonance-based gas sensor , 2019, Journal of Computational Electronics.

[72]  Long Jin,et al.  Ultra-high sensitivity of dual dispersion turning point taper-based Mach-Zehnder interferometer. , 2019, Optics express.

[73]  M. Hernáez,et al.  Lossy Mode Resonance Generation by Graphene Oxide Coatings Onto Cladding-Removed Multimode Optical Fiber , 2019, IEEE Sensors Journal.

[74]  Lin Zhang,et al.  Black phosphorus based fiber optic biosensor for ultrasensitive cancer diagnosis. , 2019, Biosensors & bioelectronics.

[75]  Chunlian Lu,et al.  Fiber Mach-Zehnder-interferometer-based liquid crystal biosensor for detecting enzymatic reactions of penicillinase. , 2019, Applied optics.

[76]  C. Chan,et al.  Reflection-Based Thin-Core Modal Interferometry Optical Fiber Functionalized With PAA-PBA/PVA for Glucose Detection Under Physiological pH , 2019, Journal of Lightwave Technology.

[77]  Tuan Guo,et al.  In-Situ Detection of Small Biomolecule Interactions Using a Plasmonic Tilted Fiber Grating Sensor , 2019, Journal of Lightwave Technology.

[78]  Long Jin,et al.  Photoacoustic computed tomography with lens-free focused fiber-laser ultrasound sensor. , 2019, Biomedical optics express.

[79]  Katsuya Kato,et al.  Enzyme immobilisation on poly-l-lysine-containing calcium phosphate particles for highly sensitive glucose detection , 2019, RSC advances.

[80]  Derek Abbott,et al.  Localized surface plasmon resonance biosensor: an improved technique for SERS response intensification. , 2019, Optics letters.

[81]  A. Farmani Three-dimensional FDTD analysis of a nanostructured plasmonic sensor in the near-infrared range , 2019, Journal of the Optical Society of America B.

[82]  Yu Zhang,et al.  Optofluidic twin-core hollow fiber interferometer for label-free sensing of the streptavidin-biotin binding , 2018, Sensors and Actuators B: Chemical.

[83]  Carlo Molardi,et al.  Etched Fiber Bragg Grating Biosensor Functionalized with Aptamers for Detection of Thrombin , 2018, Sensors.

[84]  Qi Wang,et al.  A High-Birefringence Microfiber Sagnac-Interferometer Biosensor Based on the Vernier Effect , 2018, Sensors.

[85]  Adrien E Desjardins,et al.  All-optical forward-viewing photoacoustic probe for high-resolution 3D endoscopy , 2018, Light: Science & Applications.

[86]  Stephen P. Morgan,et al.  Highly sensitive label-free antibody detection using a long period fibre grating sensor , 2018, Sensors and Actuators B: Chemical.

[87]  Jixuan Wu,et al.  Side-hole-fiber based microfluidic biosensor for label-free DNA hybridization kinetics detection , 2018 .

[88]  Long Jin,et al.  Label-free FBG biosensor for diagnosis on acute cardiovascular disease , 2018 .

[89]  R. Verma,et al.  Sensitivity enhancement of a lossy mode resonance based tapered fiber optic sensor with an optimum taper profile , 2018, Journal of Physics D: Applied Physics.

[90]  P. Torres,et al.  Performance Analysis of a Mach–Zehnder Interferometer Based on Dual-Core Transversally Chirped Microstructured Optical Fiber for Biosensing applications , 2018, 2018 International Conference on Electromagnetics in Advanced Applications (ICEAA).

[91]  Yunxuan Wang,et al.  D-Shaped photonic crystal fiber biosensor based on silver-graphene , 2018, Optik.

[92]  Yong Zhao,et al.  High-sensitivity Sagnac-interferometer biosensor based on exposed core microstructured optical fiber , 2018, Sensors and Actuators B: Chemical.

[93]  Sven Schulze,et al.  Femtosecond-Pulsed Laser Written and Etched Fiber Bragg Gratings for Fiber-Optical Biosensing , 2018, Sensors.

[94]  Vasilis Ntziachristos,et al.  Looking at sound: optoacoustics with all-optical ultrasound detection , 2018, Light: Science & Applications.

[95]  Xinran Dong,et al.  Highly sensitive refractive index sensor based on novel Mach–Zehnder interferometer with multimode fiber–thin core fiber–multimode fiber structure , 2018, Japanese Journal of Applied Physics.

[96]  M. Yilmaz,et al.  Surface-enhanced Raman spectroscopy (SERS): an adventure from plasmonic metals to organic semiconductors as SERS platforms , 2018 .

[97]  T. Nasilowski,et al.  Dual-core all-fiber integrated immunosensor for detection of protein antigens. , 2018, Biosensors & bioelectronics.

[98]  Nianbing Zhong,et al.  Study on spectral and refractive index sensing characteristics of etched excessively tilted fiber gratings. , 2018, Applied optics.

[99]  Hwa-Yaw Tam,et al.  Optofluidics in Microstructured Optical Fibers , 2018, Micromachines.

[100]  Changyu Shen,et al.  Simple immunoglobulin G sensor based on thin core single-mode fiber , 2018 .

[101]  Dag Roar Hjelme,et al.  LSPR and Interferometric Sensor Modalities Combined Using a Double-Clad Optical Fiber , 2018, Sensors.

[102]  Qi Wang,et al.  A comprehensive review of lossy mode resonance-based fiber optic sensors , 2018 .

[103]  Hongrui Jiang,et al.  Fiber-Optic Biological/Chemical Sensing System Based on Degradable Hydrogel , 2018, IEEE Sensors Journal.

[104]  Shuguang Li,et al.  Glucose sensor realized with photonic crystal fiber-based Sagnac interferometer , 2017 .

[105]  I. Papakonstantinou,et al.  Ultrasensitive plano-concave optical microresonators for ultrasound sensing , 2017 .

[106]  Vasilis Ntziachristos,et al.  Fiber interferometer for hybrid optical and optoacoustic intravital microscopy , 2017 .

[107]  Gang-Ding Peng,et al.  Label-free detection of bovine serum albumin based on an in-fiber Mach-Zehnder interferometric biosensor. , 2017, Optics express.

[108]  Bai-Ou Guan,et al.  High-sensitivity DNA biosensor based on microfiber Sagnac interferometer. , 2017, Optics express.

[109]  Bai-Ou Guan,et al.  Fiber-Laser-Based Ultrasound Sensor for Photoacoustic Imaging , 2017, Scientific Reports.

[110]  Wei Shi,et al.  Non-interferometric photoacoustic remote sensing microscopy , 2017, Light: Science & Applications.

[111]  Cheng Sun,et al.  Optical Detection of Ultrasound in Photoacoustic Imaging , 2017, IEEE Transactions on Biomedical Engineering.

[112]  Lan Jiang,et al.  Fiber optofluidic biosensor for the label-free detection of DNA hybridization and methylation based on an in-line tunable mode coupler. , 2016, Biosensors & bioelectronics.

[113]  B. D. Gupta,et al.  Simultaneous estimation of vitamin K1 and heparin with low limit of detection using cascaded channels fiber optic surface plasmon resonance. , 2016, Biosensors & bioelectronics.

[114]  K. V. Kozadaev,et al.  Michelson Interferometer based Refractive Index Biosensor , 2016 .

[115]  Q. Sui,et al.  Label-Free Immunosensor Based on Optical Fiber Fabry–Perot Interferometer , 2016, IEEE Sensors Journal.

[116]  Luís Coelho,et al.  Aptamer-based fiber sensor for thrombin detection , 2016, Journal of biomedical optics.

[117]  Q. Sui,et al.  Optical fiber Fabry–Perot interferometer for microorganism growth detection , 2016 .

[118]  C. Caucheteur,et al.  Small biomolecule immunosensing with plasmonic optical fiber grating sensor. , 2016, Biosensors & bioelectronics.

[119]  Andrea Cusano,et al.  Lab-on-fiber technology: a new vision for chemical and biological sensing. , 2015, The Analyst.

[120]  J. Lammertyn,et al.  Smart design of fiber optic surfaces for improved plasmonic biosensing. , 2015, New biotechnology.

[121]  K. S. Vasu,et al.  Sensitive detection of C-reactive protein using optical fiber Bragg gratings. , 2015, Biosensors & bioelectronics.

[122]  Sankhyabrata Bandyopadhyay,et al.  Sensitivity Enhancement of Turn-Around-Point Long Period Gratings By Tuning Initial Coupling Condition , 2015, IEEE Sensors Journal.

[123]  Tanya M Monro,et al.  Dip biosensor based on localized surface plasmon resonance at the tip of an optical fiber. , 2014, Langmuir : the ACS journal of surfaces and colloids.

[124]  Francisco J. Arregui,et al.  A Lossy Mode Resonance optical sensor using silver nanoparticles-loaded films for monitoring human breathing , 2013 .

[125]  K. Grattan,et al.  Wavelength-based localized surface plasmon resonance optical fiber biosensor , 2013 .

[126]  Seung-Ki Lee,et al.  Real-time label-free immunoassay of interferon-gamma and prostate-specific antigen using a Fiber-Optic Localized Surface Plasmon Resonance sensor. , 2013, Biosensors & bioelectronics.

[127]  Francisco J. Arregui,et al.  Fiber-optic biosensor based on lossy mode resonances , 2012 .

[128]  Antonello Cutolo,et al.  Lab-on-fiber technology: toward multifunctional optical nanoprobes. , 2012, ACS nano.

[129]  Wei W. Yu,et al.  Optofluidic SERS: synergizing photonics and microfluidics for chemical and biological analysis , 2012, Microfluidics and Nanofluidics.

[130]  Ian M. White,et al.  Optofluidic SERS: synergizing photonics and microfluidics for chemical and biological analysis , 2012 .

[131]  Nan Wu,et al.  Tapered Optical Fiber Sensor for Label-Free Detection of Biomolecules , 2011, Sensors.

[132]  R. Lindquist,et al.  A reflection-based localized surface plasmon resonance fiber-optic probe for biochemical sensing , 2011, Biomedical optics express.

[133]  A. Dhawan,et al.  Plasmonic Structures Based on Subwavelength Apertures for Chemical and Biological Sensing Applications , 2008, IEEE Sensors Journal.

[134]  Libo Yuan,et al.  In-fiber integrated Michelson interferometer. , 2006, Optics letters.

[135]  C. Caucheteur,et al.  Demodulation technique for weakly tilted fiber Bragg grating refractometer , 2005, IEEE Photonics Technology Letters.

[136]  Brian Culshaw,et al.  The optical fibre Sagnac interferometer: an overview of its principles and applications , 2005 .

[137]  H. Chan,et al.  Ultrasonic hydrophone based on distributed Bragg reflector fiber laser , 2005, IEEE Photonics Technology Letters.

[138]  J. Homola Present and future of surface plasmon resonance biosensors , 2003, Analytical and bioanalytical chemistry.

[139]  S. James,et al.  Optical fibre long-period grating sensors: characteristics and application , 2003 .

[140]  A. Othonos Fiber Bragg gratings , 1999 .

[141]  T. Miya,et al.  Ultimate low-loss single-mode fibre at 1.55 μm , 1979 .

[142]  E. Kretschmann Die Bestimmung optischer Konstanten von Metallen durch Anregung von Oberflächenplasmaschwingungen , 1971 .

[143]  A. Otto Excitation of nonradiative surface plasma waves in silver by the method of frustrated total reflection , 1968 .

[144]  K. Kao,et al.  Dielectric-fibre surface waveguides for optical frequencies , 1966 .

[145]  R. Wood XLII. On a remarkable case of uneven distribution of light in a diffraction grating spectrum , 1902 .

[146]  R. Wood,et al.  On a Remarkable Case of Uneven Distribution of Light in a Diffraction Grating Spectrum , 1902 .