Reflective Interferometer Research Articles

Research on high sensitivity optical fiber sensing method for simultaneous measurement of seawater velocity and temperature

Aiming at the need of high sensitivity flow velocity and temperature sensor in ocean research, an optical fiber sensor for the simultaneous measurement of seawater velocity and temperature was proposed by coupling a reflective Panda fiber polarization interferometer with a hollow cylindrical cantilever, which combining the stress sensitivity of Panda fiber and optical vernier effect to achieve simultaneous measurement and sensitization of flow velocity and temperature. Firstly, the theoretical formulas of velocity sensitivity and temperature sensitivity were obtained by theoretical derivation and finite element simulation. Secondly, a velocity and temperature measurement system was established experimentally, and the maximum velocity sensitivity was –233.86 nm/(m/s) at 0.42 m/s with the mean relative error compared with the theoretical sensitivity was 3.8 %, the maximum temperature sensitivity was −14.5 nm/(°C) with the mean relative error compared with the theoretical sensitivity was 8 %. Finally, nine different sets of seawater velocity and temperature were measured using the sensitivity matrix and compared with the Acoustic Doppler Velocimetry and Conductivity-Temperature-Depth meter, the mean relative error of velocity and temperature measurement results were 2.8 % and 2 %, respectively. The optical fiber sensor based on the cantilever is expected to play an important role in the field of ocean flow field measurement because of high sensitivity and the ability to measure velocity and temperature simultaneously.

Fast repeatable measurement of hydrogen concentration based on a reflective fiber hybrid interferometer probe with vernier effect

A hydrogen (H2) sensor based on hybrid Fabry-Perot interference (FPI) and Michelson interference (MI) with Vernier effect is demonstrated. The optical probe is manufactured by fusing a multimode fiber (MMF) and a double-side hole fiber (DSHF) between a single-mode fiber (SMF) and a hollow core fiber (HCF) filled with polydimethylsiloxane (PDMS) at the end to form a cascaded FP and MI, which can generate a vernier envelope. by fusing a multimode fiber (MMF) and a double-side hole fiber (DSHF) between a single-mode fiber (SMF) and a hollow core fiber (HCF) filled with PDMS at the end. To accomplish H2 sensing, palladium-tungstic oxide (Pd-WO3) powder is attached to the exterior surface of PDMS, which will cause an exothermic redox reaction with H2. The released heat will lead to the volume expansion of PDMS with remarkable thermal response characteristics, and finally cause the movement of the vernier-like spectral envelope with the variation of H2 concentration. The sensitivity of the proposed sensor is 2.2 nm/% in the range of 0 %–1% through the H2 measurement experiment. For H2 with a concentration of 1 %, it has the response time of 28 s and shows good reversibility in the cyclic experiment. In addition, the sensitivity of temperature and relative humidity (RH) is 0.21 nm/°C and 0.0014 nm/%RH, respectively. The proposed sensor adopts a reflective probe, which is compact in structure and small in volume, and shows fast response and excellent repeatability. It has great advantages in H2 measurement in narrow spaces and long distances.

Target and cantilever supported seawater velocity sensor based on panda fiber polarization interferometer.

It is necessary to develop a novel optical low velocity sensor for seawater. In this paper, a fiber optic seawater velocity sensor based on a target cantilever reflective polarization interferometer is presented theoretically and experimentally. Height: width of equal strength cantilever is determined by finite element method as 22:5, and the seawater velocity sensing experiment is carried out using this parameter. The sensitivity obtained by experiment is consistent with the theory, whose correlation coefficient is 0.96, and the mean relative error is 3.65%. The velocity measurement results of the sensor were also compared by Acoustic doppler velocimetry, the correlation coefficient and the mean relative error are 0.92 and 4.5% respectively, which realized the high precision measurement of water velocity. The maximum sensitivity of the sensor is 355.55 nm/(m·s-1) when the velocity is 0.09 m/s. In addition, when the thickness of the cantilever is 0.5 mm, the velocity measurement can be realized in the range of 0-0.22 m/s. Finally, the influence factors of sensor sensitivity are discussed, which shows that the sensitivity is related to wavelength, velocity and the size of the cantilever structure, and is independent on the length of the panda fiber. The fiber optic velocity sensor based on the target cantilever is expected to play an important role in the field of seawater measurement due to its advantages of small size, stable structure and high sensitivity.

Excess noise suppression in fiber-optical current sensors with small-radius coiling of the spun fiber

The effect of bending of a high-birefringent spun fiber on excess noise suppression in a Faraday fiber-optic current sensor based on a reflective interferometer is investigated. It is theoretically shown, that spun fiber winding with a small radius results in the emergence of undesired secondary waves in the interferometer. These waves partially fade out in the polarizer of the sensor, which leads to deformation of the optical spectrum and, in turn, to a reduction of excess noise suppression. The form of the interference pattern is refined taking into account the strong bending of the spun fiber. The theoretical model has been experimentally confirmed by acquiring a deformed spectrum for the winding radius of 5 mm and measuring the suppression coefficients for several configurations of fiber winding.

Design of metal-dielectric interference coatings

Subject of study. Multilayer structures comprising a thin metal layer facilitate the creation of new optical schemes for spectroscopy (selectors for laser cavities, multibeam reflection interferometers, and interference filters with thin absorbing layers). Method. Methods for the calculation of complex optical coatings are constantly improved. The novelty of this work is the design of a stacked structure with a thin metal layer when a conductive surface model is used to mathematically describe the properties of this layer. Results. This work presents numerical modeling of several multilayer metal-dielectric structures. A graphical method for designing an asymmetric front mirror of a reflection interferometer that uses circular charts of a complex reflection coefficient ensures visual clarity when searching for an optimal solution. The proposed multilayer structure with thin metal films placed at the layer boundaries ensures effective suppression of the reflected light with wavelengths different from the selected one. A narrow extrema (maxima and minima) transformation in the spectral or angular dependences of the reflection coefficient is shown to occur in the case of the oblique incidence of s-polarized light on the multibeam reflection interferometer and the variation of the “gap” thickness. It is established that, if a thin metal film is added to the front mirror, narrow bright fringes of reflected light can be obtained in a scheme with a Fabry-Perot interferometer in addition to the fringes in transmitted light. Practical significance. The obtained results can be applied to spectroscopy.

Experimental implementation of a spectral refractive index sensor based on a reflection interferometer

Experimental study of the sensor in the Kretschmann optical scheme, in which the sensitive element is a reflection interferometer (RI) for the oblique incidence of light, is presented for the first time. A brief theory of RI is given. The experimental sample was used to measure the refractive index of the residual atmosphere in a vacuum chamber during its pumping. The high Q-factor of the RI resonator made it possible to obtain a fairly narrow spectral maximum with a width of 1.7 nm. The spectral sensitivity of the sensor was 1000 nm/RIU and the quality parameter was 529 RIU-1, it was also demonstrated that resolution of 6.5·10-8 RIU can be achieved. Proposals for further improvement of the sensor characteristics are formulated. Keywords: reflection interferometer, total internal reflection, refractive index sensor.

Angular properties of refractive index sensor based on reflection interferometer

The angular properties of sensor, implemented in Kretschmann?s scheme, where the optimized for oblique incidence of light thin-film reflection interferometer acts as a sensing element, are described in the paper. Analytical equations, defining the sensor?s properties for S and P polarization states at working wavelength in vicinity of working angle of incidence, are provided, as well as approximate equations for main parameters of sensor: sensitivity, angular full width at half maximum, contrast and figure of merit. The possibility to vary the named parameters by choosing appropriate metal and dielectric layers of the structure is shown. For an example, the numerical calculations are made for one of special cases, optimized for S polarization state, as having larger figures of merit. The dependencies of angular properties on number of layers and base thickness are demonstrated. It is shown, that angular measurements with this method are theoretically capable of infinite figures of merit, and in practice they are only limited by losses in layered structure and beam divergency. The recommendations for experimental realization of method are given. Keywords: reflection interferometer, total internal reflection, refractive index sensor.

Экспериментальная реализация спектрального сенсора коэффициента преломления на основе отражательного интерферометра

Experimental study of the sensor in the Kretschmann optical scheme, in which the sensitive element is a reflection interferometer (RI) for the oblique incidence of light, is presented for the first time. A brief theory of RI is given. The experimental sample was used to measure the refractive index of the residual atmosphere in a vacuum chamber during its pumping. The high Q-factor of the RI resonator made it possible to obtain a fairly narrow spectral maximum with a width of 1.7 nm. The spectral sensitivity of the sensor was 1000 nm / RIU and the quality parameter was 529 RIU–1, it was also demonstrated that resolution of 6.5 10-8 RIU can be achieved. Proposals for further improvement of the sensor characteristics are formulated.

Single-path electro-optic coefficients measurement approach using multiple reflection interference.

An electro-optic coefficient (EOC) is an important optical property of optical crystals. In this work, a single-path multiple reflection interferometer is proposed to measure the components of signed EOCs with high precision. With the help of the normalization method, the influence of incident light was removed, and repeatability of the experimental results was improved. The signed EOCs of a congruent LiNbO3 crystal were determined under a small external electric field as γ31=+9.6±0.3pm/V and γ33=+29.5±0.5pm/V. This study may contribute to the development of potential anisotropic devices of optical crystals.

Surface quality control of thin SiN layer by optical measurements

Fiber optic interferometers have a wide range of applications including biological and chemical measurements. Nevertheless, in case of a reflective interferometer setup, standard silver mirrors cannot be used in every measurement, due to their chemical activity. In this work, we investigate the surface quality of a thin optical layer of silicon nitride (SiN) which can serve as an alternative material for silver mirrors. We present measurements carried out with a Fabry-Perot fiber optic interferometer working in a reflective mode. Measurement results allow us to determine the surface quality of the investigated layer. Full Text: PDF ReferencesK. Karpienko, M.S. Wróbel, M. Jedrzejewska-Szczerska, "Determination of refractive index dispersion using fiber-optic low-coherence Fabry-Perot interferometer: implementation and validation", Opt Express, 53, 077103 (2014). CrossRef Jedrzejewska-Szczerska M., Gnyba M., Kosmowski B. B. "Low-coherence fibre-optic interferometric sensors", Acta Phys. Pol. A 120, 621 (2011). CrossRef M. Jedrzejewska-Szczerska "Response of a new low-coherence Fabry-Perot sensor to hematocrit levels in human blood",Sensors 14(4), 6965 (2014). CrossRef M. Kosowska, D. Majchrowicz, K.J. Sankaran, M. Ficek, K. Haenen, M. Szczerska, "Doped Nanocrystalline Diamond Films as Reflective Layers for Fiber-Optic Sensors of Refractive Index of Liquids", Materials 12, 2124 (2019). CrossRef Shou-YiChang, Yi-Chung Huang, "Analyses of interface adhesion between porous SiO2 low-k film and SiC/SiN layers by nanoindentation and nanoscratch tests", Microelectron. Eng. 84(2), 319 (2007). CrossRef X. Wang, C. Wang, X. Shen, F. Sun, "Potential Material for Fabricating Optical Mirrors: Polished Diamond Coated Silicon Carbide". Appl. Opt. 56, 4113 (2017). CrossRef G. Coppola, P. Ferraro, M. Iodice, S. De Nicola, "Method for measuring the refractive index and the thickness of transparent plates with a lateral-shear, wavelength-scanning interferometer", Appl. Opt. 42, 3882 (2003). CrossRef H. Mäckel, R. Lüdemann, "Detailed study of the composition of hydrogenated SiNx layers for high-quality silicon surface passivation", J. Appl, Phys. 92, 2602 (2002). CrossRef N. Atman, M. Krzywinski, "Visualizing samples with box plots", Nat. Methods, 11(2), 119 (2014). CrossRef M. Vignesh, R. Balaji, "Data analysis using Box and Whisker Plot for Lung Cancer", International Conference on Innovations in Power and Advanced Computing Technologies,(2017). CrossRef

Spectral Characteristics of an Oblique-Incidence Reflection Interferometer as a Refractive Index Sensor

A sensor of refractive index of analytical liquid operating in the Kretschmann geometry and based on an oblique-incidence reflection interferometer (RI) is simulated for the first time, and its spectral properties are investigated. The principle of operation of the sensor is based on the effect of inverted surface plasmon resonance (ISPR). The sensitive structure represents the metal–dielectric multilayer coating consisting of thin nickel film in combination with quarter-wave dielectric layers. Simulation of the principle of RI fabrication under oblique incidence of light is described. Expressions governing sensitivity, spectral width of the ISPR-induced maximum in reflection, along with the figure of merit, are derived. It is demonstrated that this type of sensor can exhibit extremely high values of the figure of merit (>103) due to high Q factor.

Спектральные характеристики наклонного отражательного интерферометра как сенсора показателя преломления

The paper presents simulation of the refractive index sensor of the analyzed liquid in the Kretschmann configuration based on an oblique reflective interferometer (RI) and its spectral properties for the first time. The principle of operation of this sensor is based on the effect of inverted surface plasmon resonance (ISPR). The sensitive structure is the metal-dielectric multilayer coating based on a nickel thin film in combination with non-quartewavelength dielectric layers. Modeling of the RI manufacturing process under oblique light incidence is described. Formulas for estimating the sensitivity and spectral width of the reflection maximum of ISPR are given, as well as the figure of merit. It is shown that due to the high quality factor, this type of sensor can have very large figure of merit (>10^3).

Угловые характеристики сенсора коэффициента преломления на основе отражательного интерферометра

The angular properties of sensor, implemented in Kretschmann’s scheme, where the optimized for oblique incidence of light thin-film reflection interferometer acts as a sensing element, are described in the paper. Analytical equations, defining the sensor’s properties for S and P polarization states at working wavelength in vicinity of working angle of incidence, are provided, as well as approximate equations for main parameters of sensor: sensitivity, angular full width at half maximum, contrast and figure of merit. The possibility to vary the named parameters by choosing appropriate metal and dielectric layers of the structure is shown. For an example, the numerical calculations are made for one of special cases, optimized for S polarization state, as having larger figures of merit. The dependencies of angular properties on number of layers and base thickness are demonstrated. It is shown, that angular measurements with this method are theoretically capable of infinite figures of merit, and in practice they are only limited by losses in layered structure and beam divergency. The recommendations for experimental realization of method are given.

Аналитическое описание спектральных характеристик сенсора коэффициента преломления на основе отражательного интерферометра

The analytical formulas, describing spectral properties of sensor based on oblique incidence reflection interferometer in Kretschmann optical scheme. The sensor is designed for measuring the refractive index of analyte (liquid or gas) exploiting the effect of total internal reflection in multilayered metal-dielectric structure. The properties of comprised in the structure thin metal layer, that are necessary for optimization of sensor’s spectral profile, are defined. The spectral profile represents peaks with varying width. The oblique quaterwave dielectric layers are also used in the structure. The analytical properties of sensor depending on light polarization are given: resolution, sensitivity, contrast and figure of merit (FOM). It is shown in the paper, that sensor shows high grade parameters in both polarizations, but it is preferably to use S polarization to maximize FOM due to higher finesse in the sensor structure. The method of fabrication of such sensor structure with optical control during vacuum sputtering is proposed.

High sensitivity demodulation of a reflective interferometer-based optical current sensor using an optoelectronic oscillator.

A novel, to the best of our knowledge, interrogation scheme based on an optoelectronic oscillator (OEO) with high sensitivity and high speed response for a fiber optical current sensor utilizing a reflective interferometer is proposed and experimentally demonstrated. Due to the Faraday effect, a magneto-optic phase shift induced by current variation is generated between two orthogonal light waves. The polarization-dependent properties of the Mach-Zehnder modulator are used to convert the magneto-optic phase shift into the phase difference between the optical carrier and sideband, which is then mapped to the oscillating frequency shift by closing an OEO loop. A high current sensitivity of 152.5 kHz/A with a range of 0-2.5 A is obtained in the experiment.

In-situ DNA hybridization detection based on a reflective microfiber probe.

A label-free biosensor based on a reflective microfiber probe for in-situ real-time DNA hybridization detection is proposed and experimentally demonstrated. The microfiber probe is simply fabricated by snapping a non-adiabatic biconical microfiber through closing the oxyhydrogen flame during fiber stretching. Assisted with the Fresnel reflection at the end of microfiber, a reflective microfiber modal interferometer is realized. The in-situ DNA hybridization relies on the surface functionalization of a monolayer of Poly-L-lysine (PLL) and synthetic DNA sequences that bind to a given target with high specificity. The detection processes of DNA hybridization in various concentration of target DNA solutions are monitored in real-time and the experimental results present a minimum detectable concentration of 10pM with good repeatability. Additionally, the detection specificity is also investigated by immersing the microfiber probe into the non-complementary ssDNA solutions and observing the spectral variation. The proposed biosensor has advantages of high sensitivity, compact size, ease of use and simple fabrication, which makes it has great potential to be applied in a lot of fields such as disease diagnosis, medicine, and environmental science.

Practical reflective birefringent fiber interferometer sensor.

This paper proposes a simple and practical reflective birefringent fiber interferometer sensor that consists of a polarization beam splitter, a polarization-maintaining transmission fiber, and a sensor unit comprising two segments of birefringent fibers and a thin-film reflector. This sensor could be used for dual parameter sensing. Experiments with different temperatures and lateral loads applied to the sensor unit demonstrated temperature and load sensitivity of ∼0.0010 nm/°C and 0.298nm/N, respectively. Further study showed that temperature-insensitive lateral load measurement can be achieved by using equal length of birefringent fibers and performing differential wavelength measurement. The sensor is robust against environmental disturbance on the transmission fiber, making it potentially attractive for practical field applications.

The Cavity of a Laser with an Interferential–Polarizational Filter Based on Phase Interferometers

It is proposed to use the phase properties of a reflective interferometer upon oblique incidence for spectral selection in lasers. The effect is achieved due to the difference in phases of waves having different polarization and reflected from the reflective interferometer. A simple version in which the wave is incident at the Brewster angle on the reflective interferometer in the form of a plate with a single totally reflecting face is considered for several materials of the plate. It is shown that one such element can replace several plates of Lyot-type filters. A cavity with two reflective interferometers has been calculated; in this cavity, one can multiply increase the selectivity. A version of a cavity with a reflective interferometer in the form of a thin-layer coating is considered; for this cavity, a mechanism for a twofold increase in the free dispersion region due to inclusion of a metal layer into the coating is proposed. Results of calculating a specific device for a wavelength of 0.6 μm are presented.

Method for manufacturing a fibre reflection interferometer based on a metal-dielectric diffraction structure

A new method for manufacturing a two-mirror reflection fibre interferometer in a single-mode fibre consisting of an input mirror with an asymmetric reflection coefficients and a highly reflective end mirror is presented and experimentally demonstrated. The input mirror is based on a metal-dielectric diffraction structure in the form of an aperture in an aluminium film and a dielectric multilayer coating, which provides asymmetry of the reflection coefficient. The method includes the calculation of the energy coefficients of the aluminium film with a hole, the determination of the optimal diameter of the hole, as well as making of the hole, the entrance mirror and the resonator with a short fibre base. A sample interferometer is demonstrated that has an increased (at least by two orders of magnitude) radiation resistance compared to variants based on a continuous metal film, namely, at least 100 mW of radiation in a single-mode SMF-28e fibre at a wavelength of 1550 nm.

In-line reflective Mach-Zehnder interferometer based on a tilted in-fiber beam splitter.

A fiber in-line reflective Mach-Zehnder interferometer is proposed and experimentally demonstrated, which is based on a tilted in-fiber beam splitter inscribed by a femtosecond laser. The beam splitter splits the incident light beam into two parts; one is directed to the fiber cladding-air interface, where it experiences total internal reflection and is directed to the fiber core. The other part of the light beam keeps traveling in the fiber core. The two parts of the light beams are recombined in the fiber core to generate interference before being reflected at the fiber cut end face. The device proposed is compact in size, robust in mechanical strength, easy in fabrication, and can be used for environmental refractive index sensing in a convenient manner.