Yuriy Nikolaevich Kulchin

Fast adaptive interferometer on dynamic reflection hologram in CdTe:V.

We present an adaptive interferometer based on the reflection dynamic hologram recorded in photorefractive CdTe:V crystal with no external electric field. Linear phase-to-intensity transformation is achieved by vectorial mixing of two waves with different polarization states (linear and elliptical) in the anisotropic diffraction geometry. Comparison of reflection and transmission geometries considering both sensitivity and adaptability is carried out. It is shown that the reflection geometry is characterized by better combination of these parameters provided that the crystal possesses high enough concentration of photorefractive centers.

Laser adaptive holographic hydrophone

A new type of a laser hydrophone based on dynamic holograms, formed in a photorefractive crystal, is proposed and studied. It is shown that the use of dynamic holograms makes it unnecessary to use complex optical schemes and systems for electronic stabilisation of the interferometer operating point. This essentially simplifies the scheme of the laser hydrophone preserving its high sensitivity, which offers the possibility to use it under a strong variation of the environment parameters. The laser adaptive holographic hydrophone implemented at present possesses the sensitivity at a level of 3.3 mV Pa-1 in the frequency range from 1 to 30 kHz.

Special Section Guest Editorial: Optics, Spectroscopy, and Nanophotonics of Quantum Dots

This PDF file contains the editorial “Special Section Guest Editorial: Optics, Spectroscopy, and Nanophotonics of Quantum Dots” for JNP Vol. 10 Issue 03

Coherent Optical Method for Studies of Nanoscale Objects in Liquid Media Based upon Spatial Averaging of Data

Correlation method for processing dynamic light scattering patterns observed when laser radiation passes through liquid media was developed. The method is based on procedure of spatial averaging of the data contained measured values of correlation functions of intensity of light scattered by moving small particles. The method allows one to measure particles diameters from 30 to 750 nm with measurement error less then 10%. The method makes it possible to decrease correlation functions measurement time down to 1 ms and provides opportunity to carry out measurements for different scattering angles simultaneously. The method offers a way of recognizing speckle pattern transformations caused by harmonic, translatory and Brownian motions of particles, and allows one to register influence of uncontrolled forces such as monochromatic and wideband acoustic fields upon particles size measurements results.

Nanostructured Metal Substrates Fabrication for Surface Enhanced Fluorescence Using the Nanosecond Speckle-Modulated Laser Pulses

Nanosecond speckle-modulated laser pulses were applied to fabricate nanotextured metal substrates for surface enhanced fluorescence (SEF) applications. The speckle-modulated patterns obtained by passing the laser nanosecond pulse through the simplest diffusive object were found suitable for fast large-scale texturing of metal films with micron-sized structures - nanojets, nanobumps and submicron through holes, previous reported only for single-shot nanoablation with tightly focused beams. The optimal regime for pattering the mm-scale areas of Au films with nanojets with an averaged recording density of 105 nanojets per square millimeter were determined and realized. The fabricated nanotextured Au substrates demonstrate spatially uniform SEF signal from the Rhodamine 6G organic dye with averaged 5-fold enhancement factor being compared with unmodified Au surface.

Quadrature Mode of Photogalvanic Autocorrelation of Ultra-Short Laser Pulses

A new mode of interferometric autocorrelation based on the linear photogalvanic effect in non-centrosymmetric crystals is proposed. It involves simultaneous measurement of two autocorrelation signals being in quadrature to each other with respect to the phase difference (time delay) of recombined laser pulses. This mode eliminates adverse influence of occasional phase difference, light intensity variations, or current saturation on the accuracy of the measurements. Possibility to obtain frequency chirping coefficients by using the quadrature mode of photogalvanic autocorrelation is discussed.

Features of monitoring of technical conditions of engineering structures with use of single-fibre multimode interferometers

The work focuses on investigation of possibilities of single-fibre multimode interferometers application to development of sensors and multichannel measurement systems for monitoring of technical conditions of engineering structures. Features of use of correlation method for processing single-fibre multimode interferometers signals were studied. Peculiarities of development of separate sensors as well as multichannel measurement systems based upon single-fibre multimode interferometers were considered. Besides, some results obtained with use of abovementioned measurement systems during experimental studies of deformational processes within reinforce concrete constructions are discussed.

Differential Reflectometry of Fiber Bragg Gratings

A reflectometric approach is proposed for interrogation of multiple fiber Bragg grating (FBG) sensors recorded in a single fiber optic line, based on the differential registration FBGs’ response to a short probing laser pulse using conventional OTDR. A special optical layout has been developed allowing transformation of FBG’s spectrally modulated signals into intensity modulated signals and at the same time eliminating the susceptibility of the system to light power fluctuations. Threshold sensitivity of the method amounted to ~50 μstrain within the measurement range of ~4000 μstrain. The maximum number of FBGs interrogated by the proposed technique is estimated at several hundred, which by far surpasses the requirements of most practical applications. Due to its simplicity, efficiency and usage of conventional OTDR equipment the proposed FBG interrogation technique can find a wide range of applications, in particular in structural health monitoring.

Fast adaptive interferometer based on CdTe crystal and low power radiation

An adaptive fiber-optical interferometer, which is based on dynamic reflection hologram recorded in the photorefractive crystal of cubic symmetry without applying any electrical field, is developed. Adaptive properties of dynamic hologram enable the solution of an interferometers working point uncontrollable drift problem caused by external factors. Theoretical analysis has allowed us to find the optimal set of parameters for both interacting waves and crystal to reach the maximal sensitivity of the measuring system. Use of semiconductor crystal CdTe with fast recording time of a dynamic hologram makes it possible to achieve high cutoff frequencies at reasonably low light intensities. As a result the measuring system is characterized by low energy consumption and ability of stable operation of long duration in industrial environment.

Fast-adaptive fiber-optic sensor for ultra-small vibration and deformation measurement

Adaptive fiber-optic interferometer measuring system based on a dynamic hologram recorded in photorefractive CdTe crystal without applying an external electric field is developed. Vectorial mixing of two waves with different polarizations in the anisotropic diffraction geometry allows for the realization of linear regime of phase demodulation at the diffusion hologram. High sensitivity of the interferometer is achieved due to recording of the hologram in reflection geometry at high spatial frequencies in a crystal with sufficient concentration of photorefractive centers. The sensitivity obtained makes possible a broadband detection of ultra-small vibrations with amplitude of less then 0.1 nm. High cut-off frequency of the interferometer achieved using low-power light sources due to fast response of CdTe crystal allows one to eliminate temperature fluctuations and other industrial noises.