Petr Agruzov

Magneto-optic effects in silica core microstructured fibers with a ferrofluidic cladding

Studies of magneto-optic effects in ferrofluid-filled silica core microstructured optical fibers are reported. Amplitude, frequency, and polarization dependencies of magneto-optic responses were measured for both the transverse and longitudinal geometries of the applied AC magnetic field. Magneto-optic responses of two types, i.e., the fast and slow one, were observed. A qualitative model based on the Neel rotation for the fast response and on particle motion and agglomeration for the slow response is proposed.

Transient magneto-optic effects in ferrofluid-filled microstructured fibers in pulsed magnetic field

Transient magneto-optic effects in ferrofluid-filled microstructured optical fibers are considered. Magneto-optic responses of two types, i.e. , an even and an odd one, were observed in the longitudinal geometry of an applied pulsed magnetic field for the kerosene-based Fe 3 O 4 ferrofluid with nanoparticles. For the first time a submicrosecond response time limited by the rise time of the applied field pulse was demonstrated for the odd magneto-optic effect in an all-fiber system, and responses of the even and odd magneto-optic effects were separated. A strong influence of the pulse width on the relaxation time of the even response is attributed to the formation of particle aggregates.

Simulation of Ti-indiffused lithium niobate waveguides and analysis of their mode structure

Simulation of Ti-indiffused waveguides on LiNbO3 is described. The influence of diffusion conditions and technological parameters on the waveguide mode structure is considered. Boundaries of multimode, single-mode, and single-mode polarizing regimes of operation are defined.

Fabrication of high extinction ratio lithium niobate integrated optical modulators using photorefractive trimming

A method for increasing the extinction ratio of integrated optical Mach-Zehnder modulators based on LiNbO3 via the photorefractive effect is proposed. The influence of the photorefractive effect on the X- and Y-splitters of intensity modulators is experimentally studied. An increase in the modulator extinction ratio by 17 dB (from 30 to 47 dB) is obtained. It is shown that fabricated modulators with a high extinction ratio are important for quantum key distribution systems.

Femtosecond laser micro-inscription and machining for high performance lithium niobate photonic integrated circuits

Lithium niobate (LN) is one of basic materials of integrated optics used, for example, for electro and acousto-optical modulators, switches, diffraction gratings, nonlinear optical wavelength converters, and others [1]. LN-based ion exchange or Ti-indiffused photolithographic techniques are established technologies, however, some modern applications, such as high-purity suppressed carrier synthesis or high extinction ratio pulse generation for precision measurement systems require the use of additional active trimming electrodes [2] and a corresponding servo loop because of finite tolerances of optical elements. Recently developed direct laser writing (DLW) with femtosecond/ultrafast laser pulses [3] can be employed to address the problem, but this method is problematic for mass production and suffer from high insertion loss in optical waveguides (typically ∼ 1 dB/cm compared to <0.1 dB/cm for Ti-indiffused waveguides).

Ferrofluid as promising magnetically controlled material for optofluidics and microstrutured fiber-based sensing

Studies of magneto-optic properties of Fe3O4 ferrofluid (colloidal solution of nanosized particles) in a pulsed and AC magnetic field are reported. It is shown that a microstructured optical fiber with cladding holes filled with ferrofluid is sensitive to the external magnetic field vector and that operating speed of magnetically controlled optofluidic devices can be increased by using a transverse biasing.

Polarizing properties of Ti-indiffused lithium niobate optical waveguides

Methods for selection, transformation, and control of light polarization in Ti-waveguides on lithium niobate (LiNbO3) substrates are described. The influence of technological parameters and waveguide topology is considered. The polarization extinction ratio higher than 40 dB/cm was experimentally demonstrated.

Generation of high extinction optical pulses by means of LiNbO3 Mach-Zehnder modulators

High extinction optical pulse generation via cw modulation in lithium niobate Mach-Zehnder integrated optical modulators is discussed, and methods for bias point stabilization and pulse shape measurements are presented. Generation of high dynamic extinction (>40 dB) optical pulses by a high static extinction lithium niobate modulator was experimentally demonstrated.

Population gratings in saturable optical fibers with randomly oriented rare-earth ions

Formation of the dynamic population gratings in optical fibers with randomly oriented rare-earth ions is analyzed with a special interest to the grating component for readout with the orthogonal light polarization. It is shown that as compared with a simple model case of the collinearly oriented dipole-like centers their random orientation leads to approximately 2-times growth of the effective saturation power P sat when it is estimated from the incident power dependence of the fiber absorption or from that of the fluorescence intensity. An optimal incident power, for which the maximum of the dynamic population grating amplitude for collinear light polarization is observed, also follows this change in P sat, while formation of the grating for orthogonal polarization needs essentially higher light power. The reduced anisotropy of the active centers, which is in charge of the experimentally observed weakening of the polarization hole burning (PHB) and of the fluorescence polarization, compensates in some way the effect of random ion orientation. The ratio between the maximum conventional (i.e. for the interacting waves collinear polarizations) two-wave mixing (TWM) amplitude and the initial not saturable fiber optical density proves to be, however, nearly the same as in the model case of collinearly oriented dipoles. The ratio between the PHB effect and the amplitude of the anisotropic grating, which is responsible for TWM of the orthogonally polarized waves, is also not influenced significantly by the reduced anisotropy of ions.

Nonstationary coherent optical effects in acetylene-filled hollow core photonic crystal fibers

We report studies of the nonstationary coherent effects, i.e., free optical induction, optical nutation, and photon echo, in a hollow-core photonic crystal fiber filled with acetylene. Nanosecond optical pulses were used in the experiments. The transverse relaxation time was estimated to be about 3 nanoseconds.