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In this study, a beta-barium borate sensing head (BBO-SH) was fabricated and evaluated for the measurements of fluidic concentration variations by using a non-invasive technique. The BBO-SH could be coupled to a fluidic container through thin interlayer water in a heterodyne interferometer based on the phase interrogation. To ensure the sensing head's stability, the package of BBO-SH uses the prism and the coverslip bounded with UV glue, which can resist environmental damage due to moisture. After each use, the sensing head could be easily cleaned. The sensitivity of the BBO-SH remained stable after repeated measurements over a period of 139 days. Finally, the achievable measurement resolutions of the concentration and refractive index are 52 ppm and 1 × 10−6 RIU, respectively, for the sodium chloride solution. The achievable measurement resolutions of the concentration and refractive index were 55 ppm and 8.8 × 10−7 RIU, respectively, for the hydrochloric acid solution. [ABSTRACT FROM AUTHOR]

A single-beam pump-probe method based on a dual-channel phase measurement system was adopted to measure photo-induced phase variations caused by the photorefractive effect. This study systematically studied the dependence of photorefractive birefringence on the propagation directions of probing lights in various electro-optic crystals at visible wavelengths. [ABSTRACT FROM AUTHOR]

A birefringence angle sensor (BAS) was proposed herein for application on a displacement measurement in a homodyne interferometer. The BAS was fabricated using a birefringence plate of potassium titanyl phosphate (KTP) immersed with glycerin liquid in a cylindrical glass container. The lateral displacement of a probe light induces a refractive angle change in the KTP through the curve interface in the glass container. According to the relationship between the displacement and the refracted angle change in the BAS, the measured phase is dependent on the angle change to further obtain actual displacements. Moreover, the flexible incident angles for a tunable sensitivity benefit the displacement measurement range determined by the proposed KTP-BAS. [ABSTRACT FROM AUTHOR]

A compact displacement sensor (CDS) was proposed to be applied as a non-intrusive concentration measurement of flowing liquid by employing a phase-interrogation in a homodyne interferometer. To verify the feasibility of the proposed CDS, a measurement setup was constructed and a series of experiments were performed. The experimental results show that a good linear property between the phase change and the concentration variation are achievable. The disposable and cheap acrylic container potentially provides simple and repeatable concentration measurements. The best measurement resolutions of the weight percentage are 0.015% and 0.013% for the flowing salt and hydrochloric acid solutions, respectively. According to the experimental results, the non-intrusive technique is also useful for real-time quality monitoring of a flowing liquid on a production line. [ABSTRACT FROM AUTHOR]

A birefringent-refraction (BR) sensor for measuring refractive indices of liquid solutions based on phase interrogation in a heterodyne interferometer is proposed. We theoretically investigate a comprehensive performance comparison between a surface plasmon resonance (SPR) sensor and the proposed BR sensor in terms of sensitivity and the dynamic range in refractive index measurements. In comparison with a typical SPR sensor, the simulations and experiments show that BR sensors can achieve the same order of sensitivity but with a flexible incident angle and a wide RI range. [ABSTRACT FROM AUTHOR]

• A birefringence beta-barium borate plate is proposed for an optical angle sensor in a homodyne interferometer. • The best measurement resolution of 1.5 × 10-5 deg is achievable with the probing light of 632.8 nm in the angular displacements of 5°. A high birefringent beta-barium borate (BBO) plate is proposed for an optical angle sensor in a homodyne interferometer. Simulations show that the angle measurement sensitivity can be improved by reducing a relative refractive index between the BBO plate and the environmental medium. Thus, the BBO plate is immersed in a square glass container filled with grapeseed oil. According to the optimization of an initial incident angle, linear dynamic measurement is achievable in the experiments for both probing wavelengths of 532 nm and 632.8 nm. Finally, the best angular displacement resolution of 1.5 × 10 - 5 ° is achievable in angular displacements of 5 ° by using the probing wavelength of 632.8 nm. [ABSTRACT FROM AUTHOR]

We propose a novel optical instrument to simultaneously measure the phase variations of both orthogonal linear polarizations in a Mach-Zehnder interferometer. An integrated Ti-indiffused LiNbO Mach-Zehnder modulator is adopted for phase modulation and the optical homodyne scheme is used to measure the phase variations in the experimental setup. By using the multiplexed capabilities and flexible designs of a -based platform, the simultaneous measurements with real-time display of output interferomertic signals, spectrum results, and phase variations for both orthogonal polarizations, have been successfully demonstrated in this study. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:334-337, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25703 [ABSTRACT FROM AUTHOR]

A low-cost polyethylene terephthalate fluidic sensor (PET-FS) is demonstrated for the concentration variation measurement on fluidic solutions. The PET-FS consisted of a triangular fluidic container attached with a birefringent PET thin layer. The PET-FS was injected with the test liquid solution that was placed in a common path polarization interferometer by utilizing a heterodyne scheme. The measured phase variation of probe light was used to obtain the information regarding the concentration change in the fluidic liquids. The sensor was experimentally tested using different concentrations of sodium chloride solution showing a sensitivity of 3.52 ×104 deg./refractive index unit (RIU) and a detection resolution of 6.25 × 10−6 RIU. The estimated sensitivity and detection resolutions were 5.62 × 104 (deg./RIU) and 6.94 × 10−6 RIU, respectively, for the hydrochloric acid. The relationship between the measured phase and the concentration is linear with an R-squared value reaching above 0.995. [ABSTRACT FROM AUTHOR]

A Zn-diffused 2 × 2 balanced-bridge optical switch is demonstrated on a Z-cut LiNbO3 substrate for the first time. A post thermal-treatment is used for precisely maintaining the 3-dB-power division of the two directional couplers in the device. The crosstalk ratio of both output waveguides is about -23 dB, while the measured propagation loss of a straight-channel waveguide is kept within the range of 1.1–1.25 dB/cm. In the design, without using electrically controllable couplers as 3-dB splitters or combiners, the total device length can be reduced to 18 mm. The switching voltage-length product is 8.5 V-cm for the TM polarized light at 1.32 μm. © 2004 Wiley Periodicals, Inc. Microwave Opt Technol Lett 41: 493–496, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.20182 [ABSTRACT FROM AUTHOR]

ABSTRACT We develop a phase interrogation optical waveguide sensor by integrating a phase modulator and a sensing transducer fabricated with the same Zn-indiffused lithium niobate substrate. The proposed sensing chip effectively reduces the footprint of the measurement setup and has the potential to provide a compact module for a portable metrology system. © 2013 Wiley Periodicals, Inc. Microwave Opt Technol Lett 55:1821-1823, 2013 [ABSTRACT FROM AUTHOR]

A novel homodyne metrology is demonstrated to simultaneously measure the dual-wavelength optical phase variations in a common-path polarization interferometer.The homodyne light sources were provided by launching the incident lights with different wavelengths into a same lithium niobate Zn-indiffused phase modulator. The LabVIEW-based instrument provides flexible signal processing and real-time data display for the measured results. © 2012 Wiley Periodicals, Inc. Microwave Opt Technol Lett 54:1464-1466, 2012; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.26855 [ABSTRACT FROM AUTHOR]

The thermally induced phase-retardation changes between two orthogonal polarizations of a propagating light while passing through some optical components have been investigated in an optical polarization-sensitive instrument. The measurements were performed in a dual-channel common-path polarization interferometer based on optical homodyne method. We study temperature dependent phase-retardation variations when the lights pass through a heated quarter-wave plate at different azimuth angles. By the way, we also successfully measure the path dependent phase-retardation changes when the lights pass through the different kinds of beam splitters under the same thermal impacts. These results show that the variations of ambient temperature will easily cause the systematical measurement errors in the optical polarization-sensitive instrument. © 2011 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:771-773, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25838 [ABSTRACT FROM AUTHOR]

We present a simple homodyne phase measurement instrument to evaluate a light-induced birefringence change in an Mg-doped congruent lithium niobate crystal by using an integrated lithium niobate Zn-indiffused phase modulator (ZIPM) for optical signal modulations.The results successfully demonstrate that the focused beam and modulated phase of the ZIPM can provide a simple pump-probe method for measuring the evolutions of light-induced birefringence changes. The detection of birefringence change at the level of 10 is lower than the conventional Senarmont compensation method. © 2010 Wiley Periodicals, Inc. Microwave Opt Technol Lett 53:367-369, 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/mop.25702 [ABSTRACT FROM AUTHOR]

An optical phase interrogation is proposed to study reflection-induced linear polarization rotation in a common-path homodyne interferometer. This optical methodology can also be applied to the measurement of the refractive index variation of a liquid solution. The performance of the refractive index sensing structure is discussed theoretically, and the experimental results demonstrated a very good ability based on the proposed schemes. Compared with a conventional common-path heterodyne interferometer, the proposed homodyne interferometer with only a single channel reduced the usage of optic elements.

Novel reflection-type homodyne chiral polarimetry is proposed for measuring the refractive index variations of a transparent plate under thermal impact. The experimental results show it is a simple and useful method for providing accurate measurements of refractive index variations. The measurement can reach a resolution of 7×10 -5 .

In this paper we have successfully demonstrated a z-propagating Zn-indiffused lithium niobate electro-optic modulator used for optical heterodyne interferometry. Compared to a commercial buck-type electro-optic modulator, the proposed waveguide-type modulator has a lower driving voltage and smaller phase variation while measuring visible wavelengths of 532 nm and 632.8 nm. We also demonstrate an optical temperature measurement system using a homemade modulator. The results show that the measurement sensitivities are almost the same values of 25 deg/°C for both the homemade and the buck-type modulators for a sensing light with a wavelength of 632.8 nm. Because photorefractive impacts are essential in the buck-type modulator at a wavelength of 532 nm, it is difficult to obtain reliable phase measurements, whereas the stable phase operation of the homemade one allows the measurement sensitivity to be improved up to 30 deg/°C with the best measurement resolution at about 0.07 °C for 532 nm.

Developments and applications of a dual-channel phase measurement system are being proposed and experimentally studied by utilizing an optical homodyne technique. In this measurement system, the phase modulation was adopted by using a near-stable Zn-indiffused lithium niobate phase modulator. The proposed method was successfully applied on the simultaneous measurements of the phase-retardation difference between a transmitted light and a reflected light after passing through a nonpolarization beam splitter. The measured stability of the phase-retardation difference was approximately 0.0013 rad.

In this paper, we develop an optical measurement system with capabilities of phase unwrapping, real-time and long-term monitoring for measuring a phase drift caused by photorefractive effects in lithium niobate phase modulators. To extract the phase-drift variations, the measurement setup uses a homodyne interferometer with a phase modulation and a Fast Fourier Transform (FFT) demodulation scheme. The phase-drift characteristics of a traditional Ti-indiffused and a Zn-indiffused phase modulator have been investigated under different applied voltages and throughput powers. These experiments were conducted as a proof-of-concept to demonstrate that the apparatus worked successfully to measure the phase drift of a device in the presence of photorefractive effects. The results indicate that the Zn-indiffused phase modulators have better photorefractive stability than the Ti-indiffused phase modulators.

A novel Zn-indiffused mode converter has been proposed and experimentally studied in an x-cut/z-propagation lithium niobate at a wavelength of 0.632 mum for the first time. The optimized phase-matching and mode-conversion voltages for maximum conversion are 12 V and -?5 V, respectively. The results show that the proposed mode converter can operate with a stable conversion efficiency of about 99.5% between TM and TE polarizations at a throughput power of 25 muW in a period of 60 min. Moreover, a comparison of optical power-handling stability between the Ti-indiffused and the Zn-indiffused channel waveguides, was explored. The encouraging results indicate that the Zn-indiffused waveguide has better power stability than the Ti-indiffused waveguide. Thus, it is expected that the proposed mode converter will have better stability than the conventional Ti-indiffused ones, especially in the visible wavelength region.