High-index contrast lithium niobate waveguides, fabricated by the High Vacuum Vapor-phase Proton Exchange (HiVac-VPE) technique, are very promising for increasing both the optical nonlinear and electro-optical efficiencies of photonic integrated devices. So as to play this role effectively, it is mandatory to know the crystallographic phase composition of waveguides and the position of protonated layers for appropriate tailoring and optimization based on the intended applications. In addition, the estimation of structural disorder and electro-optical properties of the waveguides are also of high interest. Benefiting from Raman spectroscopy, IR reflection, IR absorption, and UV-VIS absorption, the HxLi1−xNbO3 phase compositions, as well as the structural disorder in waveguides, were determined. Based on experimental data on the shift of the fundamental absorption edge, we have quantitatively estimated the electro-optic coefficient r13 in as-exchanged waveguides. The electro-optical properties of the waveguides have been found to be depending on the phase composition. The obtained results allow for reconsidering the proton exchange fabricating process of photonic nonlinear devices and electro-optic modulators based on high-index contrast channel waveguides on the LiNbO3 platform.

The pyroelectric response has been studied for electro-optic modulators utilizing X-cut LiNbO3 integrated-optical chips. Since this response induces the modulator drift that appears only at fast change of a chip temperature, it causes the temperature and temporal instabilities of integrated-optical devices utilizing these chips. This drift was significantly reduced with the aid of extra electrodes providing the significant shielding of the pyroelectric field.

Experimental study of the pyroelectric effect has been made for multi-function integrated-optical circuits (MIOC) utilizing x-cut LiNbO 3 chips. It has been experimentally established that pyroelectric voltage is proportional to the temperature scanning rate, and a voltage magnitude depends significantly on capacitances of chip parts between the MIOC electrodes. The pyroelectric effect is considered by us to be an important source of the thermal instability of MIOC. The model of the pyroelectric contribution to the MIOC thermal instability is used to suggest the new methods reducing this instability.

A permanent change in the refractive index affected by femtosecond laser pulses at a small depth (2–15 μm) under the surface of a lithium niobate crystal has been studied. Based on the technology of femtosecond writing, solutions for the problems of industrial electro-optical modulators are proposed. For interference schemes obtained by lithographic methods, a correction track with a reduced refractive index (Δn = –3 ∙ 10–3) was writing to reduce the coupling between the channels of the splitter and to increase its temperature stability. Apart from the above, a possibility of a fully femtosecond writing of a depressed cladding waveguide with a core diameter of 12 μm at small depths below the surface of a lithium niobate crystal has been demonstrated to create a noninterference electro-optical modulator based on the effect of electrooptic rotation of polarization.

Today interferometric fiber-optic gyroscopes (FOGs) reach ultimate theoretical performance and surpass well-established competitor, the ring laser gyroscopes. Due to its inherent low random noise and its scalability, FOG technology is one of the very few technologies able to cope with the applications requiring the highest performance. Recently, Optolink has presented new fiber-optic gyroscope SRS-5000 with bias performance, amongst the best closed loop fiber-optic gyroscope performance published to date. The aim of the current work was to produce and to estimate the performance of inertial measurement unit (IMU) and strapdown inertial navigation systems (SINS) pilot series on the basis of SRS-5000 FOG — IMU-5000 and SINS-5000, correspondingly. Measured device parameters (ARW around 0.000069 deg/Vh with a bias stability of better than 0.00008 deg/h) allow to assess these kind of devices as the highest-precision strategic grade fiber-optic gyroscopes' based IMU, commercially available. Pilot units of SINS-5000 show alignment accuracy limit down to RMS 0.005° in series of 9-minute alignments. Static tests show coordinates drift of ∼10 Nm over 7 days of operation. We believe the performance of these strategic-grade IMU and SINS may be useful in a range of high precision navigation, metrology, seismology, and structural sensing applications, as well as calibration of inertial test equipment.

Basic features of the construction and use of multiposition strapdown inertial navigation systems (MSINSs), which are built around sensors having different operating principles are considered. New properties of the above MSINSs, which are connected with their unification into a single structure are justified. The possibility for the raising of both their accuracy characteristics and their reliability characteristics is shown. The proposed approaches to the realization of such a possibility for the MSINSs rely on majority schemes of stochastic monitoring and on the optimization of the structure of distributed sensors.

The aim of the current work was to produce the highest bias stability fiber-optic gyroscope SRS-5000 and to evaluate its main technical characteristics. Five prototype SRS-5000 devices were comprehensively measured and evaluated. Measured devices' parameters (ARW around 69 M°/√hour with bias stability better than 8×10 -5 °/hour) allow to assess this type of devices as the highest-precision strategic grade fiber-optic gyroscopes, commercially available.

The aims of the current work are the research and development and flight tests of fiber-optic gyro for space applications VOBIS. Space-grade FOGs VOBIS are developed for the tasks of spacecraft orientation and navigation at the high orbit and are long-life radiation resistant. Its' estimated operation time is 15 years in high vacuum and radiation environment.

The aims of the current work are R&D and flight tests of fiber-optic gyro for space applications VOBIS. Space-grade FOGs VOBIS are developed for the tasks of spacecraft orientation and navigation at the high orbit and are long-life radiation resistant. Its' estimated operation time is 15 years in high vacuum and radiation environment.

Integrated-optic 1 x 2 switch utilizing electro-optically controllable Y-fed directional coupler has been fabricated in LiNbO3 substrates with proton exchange technology. Such an integrated-optic switch has the newly designed Y-branching power divider allowing for high switching contrast at the both optical output ports and low driving voltage. To obtain an acceptable value of the interaction-length-to-coupling-length ratio, the novel trimming procedure is proposed. A rather high switching contrast >= 23 dB (power extinction ratio) at any output port and 2.5 dB insertion losses were obtained for a device with the 9 mm electrodes length.

Based on experimental data on the shift of the fundamental absorption edge, we have quantitatively estimated the electro-optic coefficient r 13 in proton-exchanged waveguides containing different H x Li 1– x NbO 3 phases. The phase composition of the waveguides was determined based on IR reflectance and micro-Raman spectroscopy data. We established that the electro-optic properties of the waveguides depend on their phase composition. The results obtained allowed us to optimize the process for preparation of phase modulators based on channel waveguides in LiNbO 3 crystals.

It has been established, that proton-exchanged LiNbO3 waveguides have a marked subsurface layer with structural disorder inducing degradation of electro-optical properties of these waveguides. At the same time, such a subsurface disorder is found to be less pronounced in soft proton-exchanged (SPE) waveguides in comparison with annealed proton-exchanged (APE) ones. The experimental samples of phase modulators fabricated by SPE technique exhibit a better electro-optical efficiency compared to the LiNbO3 modulators produced by the standard and improved APE techniques.

A detailed correlation between the fabrication conditions, crystallographic phase state of HxLi1-xTaO3 waveguides and second-order optical non-linearity has been investigated by using reflected SHG measurements from the polished waveguide end face. The non-linearity, strongly reduced after the initial proton exchange, is found to be restored and even increased after annealing. However, this apparent increase in the non-linearity is accompanied by a strong degradation of the quality of the SHG reflected beam in the region of the initial as-exchanged waveguide due to beam scattering. The high temperature proton exchange technique has been shown to produce high-quality α-phase waveguides with essentially undegraded non-linear optical properties. There is no phase transition when the α-phase waveguides are fabricated by direct exchange. This phase presents the same crystalline structure as that of LiTaO3 and maintains the excellent non-linear properties of the bulk material. The results obtained are important for the design, fabrication and optimization of guided-wave non-linear optical devices in LiTaO3.

Strapdown inertial navigation systems (SINS) are basic parts of modern integrated navigation systems in various vehicles. Currently, fiber-optic gyroscopes (FOGs) with closed-loop feedback are finding increasing use for inertial navigation systems. The paper presents SINS-500K, SINS-500M and SINS-501 developed and produced by the Russian Research & Production Company Optolink with Optolink FOGs. The test results are discussed. Optolink FOGs and SINS’s are compared with similar devices of world leading manufacturers.

Temperature stability of magneto-optic sensor at a marked transient temperature gradient has been investigated. Our experimental study leads to the conclusion that the polarized gyro architecture with two quarter-wave retarders on the opposite sides of the fiber loop of Sagnac interferometer must be used to obtain a fiber-optic current sensor with the lowdrift behavior.

Multi-function integrated optics chips consisting of a linear polarizer, phase electro-optic modulators and Y-branching power divider were fabricated in x-cut LiNbO3 wafers with the aid of annealed proton exchange technique. Insertion losses, power transfer coefficient, splitting ratio and its spectral dependence were measured for Y-branching power dividers of different branching topologies based on channel waveguides. The parasitic spectral selectivity and photorefractive damage were suppressed by optimization of branching topology, introducing an extra taper with variable parameters.

A Sagnac interferometer-type fibre-optic current sensor using single-mode fibre was proposed. To prevent non-reciprocal phase en-or, depolarizers are used in the Sagnac coil. This configuration makes the current sensor less costly and rather accurate. We fabricated the current sensor for an electric power substation by using the proposed technique and confirmed its characteristics. The dynamic range of 50 dB and ratio error within +/- 0.2% were satisfied. These results have demonstrated that the Sagnac interferometer-type current sensor using a single-mode fibre is suitable as an instrument for electric power plants.

An optical voltage sensor is proposed that exploits the electric field dependence of transmission of a Mach-Zehnder interferometer fabricated on basis of the channel waveguides in electro-optic LiNbO3. The device works in a transmission scheme, utilizing the long fibre transmission lines for input and output optical signals. The sensor has been used to measure AC electric fields in a range from 0.005 to 56 kV/cm, resulting in a linear sensitivity that may be further improved by tailoring of the optical and geometrical parameters of the fibre-pigtailed Mach-Zehnder interferometer.