Showing papers on "Single-mode optical fiber published in 2012"
TL;DR: The shape of a multi-core optical fiber is calculated by numerically solving a set of Frenet-Serret equations describing the path of the fiber in three dimensions by exploiting curvature and bending direction functions derived from distributed fiber Bragg grating strain measurements in each core.
Abstract: The shape of a multi-core optical fiber is calculated by numerically solving a set of Frenet-Serret equations describing the path of the fiber in three dimensions. Included in the Frenet-Serret equations are curvature and bending direction functions derived from distributed fiber Bragg grating strain measurements in each core. The method offers advantages over prior art in that it determines complex three-dimensional fiber shape as a continuous parametric solution rather than an integrated series of discrete planar bends. Results and error analysis of the method using a tri-core optical fiber is presented. Maximum error expressed as a percentage of fiber length was found to be 7.2%.
280 citations
TL;DR: A dynamic model of thermal modal instability in large mode area fiber amplifiers allowing the pump and signal optical intensity distributions to apply a time-varying heat load distribution within the fiber is presented.
Abstract: We present a dynamic model of thermal modal instability in large mode area fiber amplifiers. This model allows the pump and signal optical intensity distributions to apply a time-varying heat load distribution within the fiber. This influences the temperature distribution that modifies the optical distributions through the thermo-optic effect thus creating a feedback loop that gives rise to time-dependent modal instability. We describe different regimes of operation for a representative fiber design. We find qualitative agreement between simulation results and experimental results obtained with a different fiber including the time-dependent behavior of the instability and the effects of different cooling configurations on the threshold. We describe the physical processes responsible for the onset of the instability and suggest possible mitigation approaches.
276 citations
TL;DR: Limpert et al. as mentioned in this paper used a large-pitch photonic-crystal fiber doped with ytterbium to provide gain and achieved state-of-the-art performance.
Abstract: Rare earth-doped fibres are a diode-pumped, solid-state laser architecture that is highly scalable in average power. The performance of pulsed fibre laser systems is restricted due to nonlinear effects. Hence, fibre designs that allow for very large mode areas at high average powers with diffraction-limited beam quality are of enormous interest. Ytterbium-doped, rod-type, large-pitch fibres (LPF) enable extreme fibre dimensions, i.e., effective single-mode fibres with mode sizes exceeding 100 times the wavelength of the guided radiation, by exploiting the novel concept of delocalisation of higher-order transverse modes. The non-resonant nature of the operating principle makes LPF suitable for high power extraction. This design allows for an unparalleled level of performance in pulsed fibre lasers. A new design of optical fibre could allow fibre lasers to reach unprecedented output powers while maintaining excellent beam quality. The design, developed by Jens Limpert and co-workers from Friedrich-Schiller Universitat, Helmholtz Institute Jena and Fraunhofer Institute for Applied Optics and Precision Engineering in Jena, Germany, uses a large-pitch photonic-crystal fibre doped with ytterbium to provide gain. The key to the fibre's performance is the delocalisation of higher order modes due to the transversal arrangement of air-holes. The concept ensures that the fibre operates with a large fundamental mode that has a high-quality beam profile and good power handling characteristics, while suppressing unwanted higher order modes. A pulsed fibre laser based on this design emitted diffraction-limited pulses containing 26 mJ of energy with an average power of 130 W.
275 citations
TL;DR: It is proposed that non-adiabatic waveguide changes play an important role in allowing energy transfer from the fundamental mode into the higher order mode, and this description of mode instabilities can explain many of the experimental observations reported to date.
Abstract: Mode instabilities, ie the rapid fluctuations of the output beam of an optical fiber that occur after a certain output power threshold is reached, have quickly become one of the most limiting effects for the further power scaling of fiber laser systems Even though much work has been done over the last year, the exact origin of the temporal dynamics of this phenomenon is not fully understood yet In this paper we show that the origin of mode instabilities can be explained by taking into account the interplay between the temporal evolution of the three-dimensional temperature profile inside of the active fiber and the related waveguide changes that it produces via the thermo-optical effect In particular it is proposed that non-adiabatic waveguide changes play an important role in allowing energy transfer from the fundamental mode into the higher order mode As it is discussed in the paper, this description of mode instabilities can explain many of the experimental observations reported to date
197 citations
TL;DR: In this article, a transmission fiber for mode division multiplexing supporting LP01 and LP11 modes, with low differential group delay, low mode coupling, and low loss for both modes is presented.
Abstract: A transmission fiber for mode division multiplexing supporting LP01 and LP11 modes, with low differential group delay, low mode coupling, and low loss for both modes is presented. Spatially and spectrally resolved mode imaging (S2 imaging) is used for characterization.
166 citations
TL;DR: In this article, a single photon generation from individual self-assembled InGaAs quantum dotscoupled to the guided optical mode of a GaAs photonic crystal waveguide was investigated, and the results obtained demonstrate that such nanostructures can be used to realize an on-chip, highly directed single photon source with single mode spontaneous emision couplinge¯¯encies in excess of 85 % and the potential to reach maximum emission rates > 1 GHz.
Abstract: Institute for Microstructural Sciences - National Research Council of Canada, Ottawa, ON, Canada(Dated: September 26, 2011)We investigate single photon generation from individual self-assembled InGaAs quantum dotscoupled to the guided optical mode of a GaAs photonic crystal waveguide. By performing confocalmicroscopy measurements on single dots positioned within the waveguide, we locate their positionswith a precision better than 0:5 m. Time-resolved photoluminescence and photon autocorrelationmeasurements are used to prove the single photon character of the emission into the propagatingwaveguide mode. The results obtained demonstrate that such nanostructures can be used to realizean on-chip, highly directed single photon source with single mode spontaneous emision couplingeciencies in excess of ˘ 85 % and the potential to reach maximum emission rates >1 GHz.
166 citations
TL;DR: A germanium strip waveguide designed for single mode transmission of light in transverse magnetic polarization generated from quantum cascade lasers at a wavelength of 5.8 μm is demonstrated.
Abstract: Mid-infrared photonics in silicon needs low-loss integrated waveguides. While monocrystalline germanium waveguides on silicon have been proposed, experimental realization has not been reported. Here we demonstrate a germanium strip waveguide on a silicon substrate. It is designed for single mode transmission of light in transverse magnetic (TM) polarization generated from quantum cascade lasers at a wavelength of 5.8 μm. The propagation losses were measured with the Fabry–Perot resonance method. The lowest achieved propagation loss is 2.5 dB/cm, while the bending loss is measured to be 0.12 dB for a 90° bend with a radius of 115 μm.
160 citations
TL;DR: The authors have developed a device that allows for monitoring the vibrations of human body evoked by living activities-breathing and cardiac rhythm and allows for obtaining dynamic strains on the sensing FBG in the range of 50-124 μ strain caused by breathing and approximately 8.3 μstrain induced by heartbeat.
Abstract: This paper shows the design of a fiber-based sensor for living activities in human body and the results of a laboratory evaluation carried out on it. The authors have developed a device that allows for monitoring the vibrations of human body evoked by living activities-breathing and cardiac rhythm. The device consists of a Bragg grating inscribed into a single mode optical fiber and operating on a wavelength of around 1550 nm. The fiber Bragg grating (FBG) is mounted inside a pneumatic cushion to be placed between the backrest of the seat and the back of the monitored person. Deformations of the cushion, involving deformations of the FBG, are proportional to the vibrations of the body leaning on the cushion. Laboratory studies have shown that the sensor allows for obtaining dynamic strains on the sensing FBG in the range of 50-124 μ strain caused by breathing and approximately 8.3 μstrain induced by heartbeat, which are fully measurable by today's FBG interrogation systems. The maximum relative measurement error of the presented sensor is 12%. The sensor's simple design enables it to be easily implemented in pilot's and driver's seats for monitoring the physiological condition of pilots and drivers.
158 citations
TL;DR: A sensitive spectroscopic sensor based on a hollow-core fiber-coupled quantum cascade laser (QCL) emitting at 10.54 μm and quartz enhanced photoacoustic spectroscopy (QEPAS) technique is reported.
Abstract: A sensitive spectroscopic sensor based on a hollow-core fiber-coupled quantum cascade laser (QCL) emitting at 10.54 μm and quartz enhanced photoacoustic spectroscopy (QEPAS) technique is reported. The design and realization of mid-IR fiber and coupler optics has ensured single-mode QCL beam delivery to the QEPAS sensor. The collimation optics was designed to produce a laser beam of significantly reduced beam size and waist so as to prevent illumination of the quartz tuning fork and microresonator tubes. SF(6) was selected as the target gas. A minimum detection sensitivity of 50 parts per trillion in 1 s was achieved with a QCL power of 18 mW, corresponding to a normalized noise-equivalent absorption of 2.7×10(-10) W·cm(-1)/Hz(1/2).
148 citations
TL;DR: The formalism developed for PMD is extended to characterize MD in fibers with multiple spatial modes and a MD vector defined in a D-dimensional extended Stokes space whose square length is the sum of the square group delays of the generalized principal states is introduced.
Abstract: Modal dispersion (MD) in a multimode fiber may be considered as a generalized form of polarization mode dispersion (PMD) in single mode fibers. Using this analogy, we extend the formalism developed for PMD to characterize MD in fibers with multiple spatial modes. We introduce a MD vector defined in a D-dimensional extended Stokes space whose square length is the sum of the square group delays of the generalized principal states. For strong mode coupling, the MD vector undertakes a D-dimensional isotropic random walk, so that the distribution of its length is a chi distribution with D degrees of freedom. We also characterize the largest differential group delay, that is the difference between the delays of the fastest and the slowest principal states, and show that it too is very well approximated by a chi distribution, although in general with a smaller number of degrees of freedom. Finally, we study the spectral properties of MD in terms of the frequency autocorrelation functions of the MD vector, of the square modulus of the MD vector, and of the largest differential group delay. The analytical results are supported by extensive numerical simulations.
140 citations
TL;DR: This paper reviews two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques and some recently reported specific technologies for fabricating such fiber opticinterferometers are presented.
Abstract: In-line fiber optic interferometers have attracted intensive attention for their potential sensing applications in refractive index, temperature, pressure and strain measurement, etc. Typical in-line fiber-optic interferometers are of two types: Fabry-Perot interferometers and core-cladding-mode interferometers. It's known that the in-line fiber optic interferometers based on single-mode fibers can exhibit compact structures, easy fabrication and low cost. In this paper, we review two kinds of typical in-line fiber optic interferometers formed in single-mode fibers fabricated with different post-processing techniques. Also, some recently reported specific technologies for fabricating such fiber optic interferometers are presented.
TL;DR: By exploiting recent developments associated with parity-time (PT) symmetry in optics, a new avenue in realizing single-mode large area laser amplifiers is proposed by utilizing the abrupt symmetry breaking transition that allows the fundamental mode to experience gain while keeping all the higher order modes neutral.
Abstract: By exploiting recent developments associated with parity–time (PT) symmetry in optics, we here propose a new avenue in realizing single-mode large area laser amplifiers. This can be accomplished by utilizing the abrupt symmetry breaking transition that allows the fundamental mode to experience gain while keeping all the higher order modes neutral. Such PT-symmetric structures can be realized by judiciously coupling two multimode waveguides, one exhibiting gain while the other exhibits an equal amount of loss. Pertinent examples are provided for both semiconductor and fiber laser amplifiers.
TL;DR: It is shown that light propagation in a group of degenerate modes of a multi-mode optical fiber in the presence of random mode coupling is described by amulti-component Manakov equation, thereby making multi- mode fibers the first reported physical system that admits true multi-component soliton solutions.
Abstract: In spite of the massive interest that the generalized Manakov equation has attracted in the past two decades, no physical system which is quantitatively described by this equation has been reported so far. In this paper we show that propagation in a group of degenerate modes of a multi-mode optical fiber satisfies this equation in the presence of random mode coupling. Consequently, this is the first reported physical system that admits true multi-component soliton solutions. The reported formalism constitutes the starting point for future studies of nonlinear effects in multi-mode fiber transmission.
TL;DR: A simple empirical model is proposed to account for linear and nonlinear noise accumulation, and to predict system performance for a wide range of distances, signal powers and optical noise levels.
Abstract: We investigate via experiments and simulations the statistical properties and the accumulation of nonlinear transmission impairments in coherent systems without optical dispersion compensation. We experimentally show that signal distortion due to Kerr nonlinearity can be modeled as additive Gaussian noise, and we demonstrate that its variance has a supra-linear dependence on propagation distance for 100 Gb/s transmissions over both low dispersion and standard single mode fiber. We propose a simple empirical model to account for linear and nonlinear noise accumulation, and to predict system performance for a wide range of distances, signal powers and optical noise levels.
TL;DR: In this article, a passive polarization delay unit was implemented in the sample beam path in order to simultaneously illuminate the sample with two different polarization states, and the orthogonal polarization components for the depth-multiplexed signals from the two input states were detected using dual balanced detection.
Abstract: Polarization sensitive optical coherence tomography (PS-OCT) is a functional imaging method that provides additional contrast using the light polarizing properties of a sample. This manuscript describes PS-OCT based on ultrahigh speed swept source / Fourier domain OCT operating at 1050nm at 100kHz axial scan rates using single mode fiber optics and a multiplexing approach. Unlike previously reported PS-OCT multiplexing schemes, the method uses a passive polarization delay unit and does not require active polarization modulating devices. This advance decreases system cost and avoids complex synchronization requirements. The polarization delay unit was implemented in the sample beam path in order to simultaneously illuminate the sample with two different polarization states. The orthogonal polarization components for the depth-multiplexed signals from the two input states were detected using dual balanced detection. PS-OCT images were computed using Jones calculus. 3D PS-OCT imaging was performed in the human and rat retina. In addition to standard OCT images, PS-OCT images were generated using contrast form birefringence and depolarization. Enhanced tissue discrimination as well as quantitative measurements of sample properties was demonstrated using the additional contrast and information contained in the PS-OCT images.
TL;DR: An iterative optimization method is employed, first in the regime of strong scattering where modes are spatially localized and can be easily selected using local pumping, and then in the weakly scattering regime, where strong spatial overlap of the modes precludes spatial selectivity.
Abstract: Active control of the spatial pump profile is proposed to exercise control over random laser emission. We demonstrate numerically the selection of any desired lasing mode from the emission spectrum. An iterative optimization method is employed, first in the regime of strong scattering where modes are spatially localized and can be easily selected using local pumping. Remarkably, this method works efficiently even in the weakly scattering regime, where strong spatial overlap of the modes precludes spatial selectivity. A complex optimized pump profile is found, which selects the desired lasing mode at the expense of others, thus demonstrating the potential of pump shaping for robust and controllable single mode operation of a random laser.
TL;DR: Using experiments and numerical simulations, it is shown that the transverse localization results in an effective propagating beam diameter that is comparable to that of a typical index-guiding optical fiber.
Abstract: We utilize transverse Anderson localization as the waveguiding mechanism in optical fibers with random transverse refractive index profiles. Using experiments and numerical simulations, we show that the transverse localization results in an effective propagating beam diameter that is comparable to that of a typical index-guiding optical fiber.
TL;DR: An all-fiber optical Fabry-Perot interferometer (FPI) strain sensor whose cavity is a microscopic air bubble is demonstrated and strain and temperature sensitivities are studied experimentally.
Abstract: We demonstrate an all-fiber optical Fabry–Perot interferometer (FPI) strain sensor whose cavity is a microscopic air bubble. The bubble is formed by fusion splicing together two sections of single-mode fibers (SMFs) with cleaved flat tip and arc fusion induced hemispherical tip, respectively. The fabricated interferometers are with bubble diameters of typically ∼100 μm. Strain and temperature sensitivities of fabricated interferometers are studied experimentally; a strain sensitivity of over 4 Pm/μe and a thermal sensitivity of less than 0.9 Pm/°C is obtained.
TL;DR: The model predicts that power can be transferred from the fundamental mode to a higher-order mode when the operating power exceeds a certain threshold, and thus provides an explanation of recently reported mode instability in multimode rare-earth doped fiber amplifiers under high average-power operation.
Abstract: We present a simple semianalytical model of thermally induced mode coupling in multimode rare-earth doped fiber amplifiers. The model predicts that power can be transferred from the fundamental mode to a higher-order mode when the operating power exceeds a certain threshold, and thus provides an explanation of recently reported mode instability in such fiber amplifiers under high average-power operation. We apply our model to a simple step-index fiber design, and investigate how the power threshold depends on various design parameters of the fiber.
TL;DR: The guiding dynamics of the rod fiber are investigated and a distinct bandgap blue-shifting is reported as function of increased signal power level and thermally induced refractive index change of therefractive index profile is explained.
Abstract: We demonstrate a high power fiber (85 μm core) amplifier delivering up to 292 Watts of average output power using a mode-locked 30 ps source at 1032 nm. Utilizing a single mode distributed mode filter bandgap rod fiber, we demonstrate 44% power improvement before the threshold-like onset of mode instabilities by operating the rod fiber in a leaky waveguide regime. We investigate the guiding dynamics of the rod fiber and report a distinct bandgap blue-shifting as function of increased signal power level. Furthermore, we theoretically analyze the guiding dynamics of the DMF rod fiber and explain the bandgap blue-shifting with thermally induced refractive index change of the refractive index profile.
TL;DR: Highly efficient coupling of photons from nanoemitters into single-mode optical fibers is demonstrated using tapered fibers and is very promising for nanoparticle sensing and single-photon sources.
Abstract: Highly efficient coupling of photons from nanoemitters into single-mode optical fibers is demonstrated using tapered fibers. 7.4 +/- 1.2 % of the total emitted photons from single CdSe/ZnS nanocrystals were coupled into a 300-nm-diameter tapered fiber. The dependence of the coupling efficiency on the taper diameter was investigated and the coupling efficiency was found to increase exponentially with decreasing diameter. This method is very promising for nanoparticle sensing and single-photon sources.
TL;DR: A number of temperature-independent ultra-sensitive microscopic sensors can be devised with the interferometers here proposed since many parameters can be converted to strain.
Abstract: All-optical-fiber Fabry-Perot interferometers (FPIs) with microcavities of different shapes were investigated. It was found that the size and shape of the cavity plays an important role on the performance of these interferometers. To corroborate the analysis, FPIs with spheroidal cavities were fabricated by splicing a photonic crystal fiber (PCF) with large voids and a conventional single mode fiber (SMF), using an ad hoc splicing program. It was found that the strain sensitivity of FPIs with spheroidal cavities can be controlled through the dimensions of the spheroid. For example, a FPI whose cavity had a size of ~10x60 μm exhibited strain sensitivity of ~10.3 pm/μe and fringe contrast of ~38 dB. Such strain sensitivity is ~10 times larger than that of the popular fiber Bragg gratings (~1.2 pm/μe) and higher than that of most low-finesse FPIs. The thermal sensitivity of our FPIs is extremely low (~1pm/°C) due to the air cavities. Thus, a number of temperature-independent ultra-sensitive microscopic sensors can be devised with the interferometers here proposed since many parameters can be converted to strain. To this end, simple vibration sensors are demonstrated.
Book•
01 Dec 2012
TL;DR: Recent progress, particularly, in semiconductor-based and LiNbO3- based components, yield the prospect of widespread applications for single-mode fibre communication, optical sensors, signal processing, and nonlinear optics.
Abstract: 1 General Background Review.- 1. Maxwell's Equations.- 2. Definitions of Various Types of Medium.- 3. Wave Equation.- 4. Description of Other Material Parameters.- 5. Boundary Conditions.- 6. Fresnel Equations.- 7. Special Examples.- 8. Separation of Longitudinal and Transverse Coordinates.- 9. Definition of Various Types of Modes.- 2 Film-Waveguides and Zig Zag Waves.- I. An Introduction of Film-Waveguides-Zig Zag Waves.- (i) Dual Concept of Ray and Wave Optics.- (ii) The A and B Waves.- (iii) Electric and Magnetic Field.- (iv) Waveguide Modes and the Total Reflection Phenomenon.- (v) Field Distribution of a Waveguide Mode.- (vi) Effective Thickness of the Waveguide and Power Flow.- (vii) Different Waveguide Modes.- II Prism-Film Couplers and Zig Zag Waves.- III Materials for Film-Waveguides and Their Losses.- 3 One-Dimensional Confinement.- 1. Guided Modes of a Slab Waveguide.- 2. Graphical Solution of the Governing Transcendental Equations.- 3. Dispersion in Thin Films.- 4 Rectangular Dielectric Waveguides.- I Introduction.- II Marcatili's Analysis.- III Circular Harmonic Analysis.- A. Analysis.- B. Computed Results.- 1. Mode Configurations.- 2. Propagation Curves.- IV Comparison of Methods.- 5 Loss Mechanisms in Dielectric Waveguides.- I Introduction.- II Radiation Loss.- III Bend Loss.- A. Velocity Approach.- B. Model Analysis.- 6 Thin-Film Waveguide Fabrication and Testing Considerations.- I Introduction.- II Dimensional Considerations.- III Circuit Fabrication.- A. Etched Waveguide Fabrication.- 1. Masking and Etching.- 2. Summary of Process.- 3. Results.- B. Ion Bombardment Fabrication.- IV Measurement Techniques.- A. Determination of Refractive Index and Thickness.- 1. Stylus Measurements.- 2. Interferometer.- 3. Abbe Refractometer.- 4. Abeles Method.- 5. Prism Coupler Method.- B. Attenuation Measurements.- V Conclusion.- 7 Electron and Ion Beam Microfabrication of Integrated Optics Elements.- Electron Beam Micropattern Definition and Fabrication.- Ion Beam Sputtering for Micropattern Processing.- Scanning Electron Microscopy.- Results of Beam Microfabrication.- Conclusions and Summary.- 8 Introduction to Optical Waveguide Fibers.- I Propagation.- 1.1 Ray Theory.- 1.2 Rays in Step Refractive Index Waveguides.- 1.3 Ray Theory for Gradient Refractive Index Waveguides.- 1.4 Mode Theory.- 1.5 Mode Theory of Step Refractive Index.- 1.6 Mode Theory of Gradient Refractive Index Fibers.- II Information Capacity.- 2.1 Pulse Broadening in Single Mode Fibers.- 2.2 Pulse Broadening in Multimode Fibers.- III Attenuation.- 9 Fiber Optics Applications.- 1. Systems Applications.- 2. Near Term Fiber Optic Data Links.- 3. Input Coupling Losses.- 10 Coupled Mode Formalism for Guided Wave Interactions.- 1. Coupled Mode Formalism.- 2. Coupling Equation.- 3. Nonlinear Interactions.- 4. Photoelastic Coupling.- 5. Coupling by a Surface Corrugation.- 6. Eigen Modes of a Perturbed Waveguide.- 11 Optical Directional Couplers.- 1. Introduction.- 2. Coupled Mode Formalism.- 3. Dual Channel Directional Coupler - Theory and Experiment.- 4. Derivation of the Coupling Coefficient.- 5. Coupling Between Planar Guides.- 6. Coupling Between Channel Guides.- 7. Multichannel Directional Coupler - Coupling Coefficient Measurement.- 8. The Coupling Coefficient Sign.- 9. Ridged Channel Waveguides and Directional Couplers.- 10. Directional Coupler - Switch Modulator.- 11. Light Multiplexing by Directional Coupling.- 12. Appendix I.- 12 Periodic Couplers.- I Introduction.- II Direct Analysis of Beam Coupling.- II.1 Spectral Representation of Electromagnetic Waves.- II.2 The Prism Coupler.- II.3 Fields in the Periodic Medium.- II.4 Fields in the Coupler.- III Reciprocal Analysis of Periodic Couplers.- III.1 The Equation for Coupling Efficiency.- III.2 Aperture Fields.- IV Design Considerations.- 13 Modulation.- 1. Introduction.- 2. Modulation Analysis.- 3. Modulator Characteristics.- 4. Characteristics of Other Modulation Techniques.- 5. Circuit Aspects of Modulators.- 6. An Example.- 14 Acousto-Optical Interactions in Guided Wave Structures.- I Introduction.- II Reviews of Acousto-Optic Interactions.- 2.1 Photoelastic Effect.- 2.2 Acousto-Optic Interaction Mechanisms.- III Acousto-Optic Interaction in Guided Wave Structure - Analysis.- 3.1 Acoustic Surface Waves and Optical Guided Waves.- 3.2 Collinear Interaction of Optical Guided Waves and Acoustic Surface Waves.- 3.3 Bragg Diffraction of Optical Guided Waves by Acoustic Surface Waves.- IV Acousto-Optic Interactions in Guided Wave Structures - Experimental Results and Discussions.- 4.1 Collinear Interaction.- 4.2 Bragg Deflection of Optical Guided Waves by Acoustic Surface Waves.- 4.3 Anisotropic Light Diffraction by Acoustic Surface Waves.- V Device Parameters for Acousto-Optic Devices.- 5.1 Efficiency.- 5.2 Bandwidths and Number of Resolvable Spots.- 5.3 Speed.- 5.4 Figures of Merit.- VI Device Applications and Conclusions.- 15 Laser Source Considerations in Integrated Optics.- I Introduction.- II Resonant Feedback Structures.- A. Dispersion Relations for Periodic Structures.- B. Lasers Using Periodic Structures as the Distributed Resonant Feedback Structure (DFB Lasers).- C. Lasers Using Periodic Structures as the Resonant Reflectors in the Fabry-Perot Type of Cavities.- D. Order-of-Magnitude Estimates.- III The Active Medium.- A. Dye Lasers.- B. Semiconductor Lasers.- C. Doped Insulating Solids.- D. Gaseous Lasers.- Appendix - Derivation of Eqs. (5) and (13).
TL;DR: Single nanodiamonds containing nitrogen vacancy defect centers are deposited on a tapered fiber of 273 nanometer in diameter providing a record-high number of 689,000 single photons per second from a defect center in a single-mode fiber.
Abstract: We present a fiber-coupled diamond-based single photon system. Single nanodiamonds containing nitrogen vacancy defect centers are deposited on a tapered fiber of 273 nanometer in diameter providing a record-high number of 689,000 single photons per second from a defect center in a single-mode fiber. The system can be cooled to cryogenic temperatures and coupled evanescently to other nanophotonic structures, such as microresonators. The system is suitable for integrated quantum transmission experiments, two-photon interference, quantum-random-number generation and nano-magnetometry.
TL;DR: Based on the structure, a simple and low-cost Mach-Zehnder interferometer (MZI) formed by cascading two peanut-shape structures in the single-mode fiber is demonstrated in this article.
Abstract: A peanut-shape fiber structure that can realize the coupling and recoupling between the fiber core mode and the cladding modes is proposed in this paper. Based on the structure, a simple and low-cost Mach-Zehnder interferometer (MZI) formed by cascading two peanut-shape structures in the single-mode fiber is demonstrated. The theory and the experimental results show that the first peanut-shape structure can couple the light energy of the core mode into the cladding modes and the second peanut-shape structure can recouple the light in the cladding modes into the core mode. A high-quality interference spectrum with a fringe visibility of about 13 dB is observed. Moreover, it has very good mechanical strength compared with the MZIs based on the tapers or the offset structures. When the interferometer length L = 22 mm, the temperature sensitivity of the device is ~ 46.8 pm/°C and the strain sensitivity is ~ 14 pm/μe. Such kind of interferometer would find potential applications in communication and sensing fields.
TL;DR: From the simulation results, it is shown that the proposed fiber has high birefringence up to the order of 10(-2), negative flattened chromatic dispersion in a broad range of wavelengths, and low confinement loss less than that of the single mode fiber.
Abstract: We propose a novel design of photonic crystal fiber (PCF) using an elliptical air hole in the core as a defected core in order to enhance the performance of modal birefringence and to control the properties of chromatic dispersion at the same time. From the simulation results, it is shown that the proposed fiber has high birefringence up to the order of 10−2, negative flattened chromatic dispersion in a broad range of wavelengths, and low confinement loss less than that of the single mode fiber. The outstanding advantage of the proposed PCF is that high birefringence, negative flattened dispersion, and low confinement loss can be achieved just by adding a small sized elliptical air hole in the core to the elliptical air hole PCF, especially at the same time.
Journal Article•
TL;DR: Enhanced tissue discrimination as well as quantitative measurements of sample properties was demonstrated using the additional contrast and information contained in the PS-OCT images.
Abstract: Polarization sensitive optical coherence tomography (PS-OCT) is a functional imaging method that provides additional contrast using the light polarizing properties of a sample. This manuscript describes PS-OCT based on ultrahigh speed swept source / Fourier domain OCT operating at 1050nm at 100kHz axial scan rates using single mode fiber optics and a multiplexing approach. Unlike previously reported PS-OCT multiplexing schemes, the method uses a passive polarization delay unit and does not require active polarization modulating devices. This advance decreases system cost and avoids complex synchronization requirements. The polarization delay unit was implemented in the sample beam path in order to simultaneously illuminate the sample with two different polarization states. The orthogonal polarization components for the depth-multiplexed signals from the two input states were detected using dual balanced detection. PS-OCT images were computed using Jones calculus. 3D PS-OCT imaging was performed in the human and rat retina. In addition to standard OCT images, PS-OCT images were generated using contrast form birefringence and depolarization. Enhanced tissue discrimination as well as quantitative measurements of sample properties was demonstrated using the additional contrast and information contained in the PS-OCT images.
TL;DR: A fiber-optic interferometric probe based on a two-mode fiber (TMF) is proposed and demonstrated for measuring the thermo-optics coefficients (TOCs) of liquid samples and the sensing responses of the probe to temperature and surrounding refractive index have been experimentally investigated.
Abstract: A fiber-optic interferometric probe based on a two-mode fiber (TMF) is proposed and demonstrated for measuring the thermo-optic coefficients (TOCs) of liquid samples. The proposed probe can be simply fabricated by fusion-splicing a short piece of TMF to a lead single mode fiber (SMF) with small lateral offset, which makes interference between LP(01) and LP(02) modes. The sensing responses of the probe to temperature and surrounding refractive index (SRI) have been experimentally investigated to show the capability of simultaneous measurements; the phase change of the reflection spectrum was related to temperature variation and the intensity change was to SRI variation. The data analysis is made not only in the spectral domain but in the Fourier domain also to effectively quantify the measurements. The TOCs of several liquid samples including water, ethanol, and acetone have been obtained with the proposed method.
TL;DR: With the use of difference arithmetic demodulation method, the temperature-curvature cross-sensitivity and light source power fluctuations effects on the proposed sensor are decreased by 94% and 91%, respectively.
Abstract: A curvature sensor based on a polarization-dependent in-fiber Mach-Zehnder interferometer (MZI) is proposed. The MZI is fabricated by core-offset fusion splicing one section of polarization maintaining fiber (PMF) between two single mode fibers (SMFs). Two independent interference patterns corresponding to the two orthogonal polarization modes for the PMF are obtained. The couple efficiency between the core mode and the cladding mode decreased with the increasing of the bending on the MZI part. The curvature variation on the MZI part can be obtained by detecting the fringe visibility of the interference patterns. A difference arithmetic demodulation method is used to reduce the effects of the light source power fluctuations and temperature cross-sensitivity. Experimental results show that maximal sensitivity of −0.882 dB/m−1 is obtained under a measurement range of 0.1 to 0.35 m−1 for the curvature sensor. With the use of difference arithmetic demodulation method, the temperature-curvature cross-sensitivity and light source power fluctuations effects on the proposed sensor are decreased by 94% and 91%, respectively.
TL;DR: In this article, the effect of varying the cladding-core radius ratio on the LP 11 adiabatic criterion is modeled, and a Laguerre-Gaussian beam is created in free space using a spatial light modulator (SLM) and coupled to a few-mode fiber.