Papers by Vladimir Minkovich
IEEE Photonics Technology Letters, Jun 1, 2006
A modal interferometer was built with tapered largemode-area microstructured optical fiber (MOF).... more A modal interferometer was built with tapered largemode-area microstructured optical fiber (MOF). The tapering was introduced by slowly stretching the fiber while it was heated with a high temperature flame torch. With this "slow-and-hot" tapering process, the MOF air holes collapse and the taper waist is transformed into a solid unclad multimode fiber. This allows the coupling between the fundamental HE 11 MOF mode and the HE 1 modes of the solid fiber. The beating of the HE 1 modes makes the transmission spectra of the taper to exhibit an oscillatory pattern. The influence of the taper geometry and wavelength on the interference pattern is discussed. The interferometer can be used for diverse applications.
Temperature-insensitive photonic crystal fiber interferometer for absolute strain sensing
Applied Physics Letters, 2007
The authors report a highly sensitive (∼2.8pm∕με) wavelength-encoded strain sensor made from a pi... more The authors report a highly sensitive (∼2.8pm∕με) wavelength-encoded strain sensor made from a piece of photonic crystal fiber (PCF) spliced to standard fibers. The authors intentionally collapse the PCF air holes over a short region to enlarge the propagating mode of the lead-in fiber which allows the coupling of only two modes in the PCF. The transmission spectrum of the interferometer is stable and sinusoidal over a broad wavelength range. The sensor exhibits linear response to strain over a large measurement range, its temperature sensitivity is very low, and for its interrogation a battery-operated light emitting diode and a miniature spectrometer are sufficient.
Photonic crystal fiber interferometer for chemical vapor detection with high sensitivity
Optics Express, 2009
IEEE Photonics Technology Letters, 2006
We report a simple and compact wavelength-encoded high-temperature sensor. It consists of a micro... more We report a simple and compact wavelength-encoded high-temperature sensor. It consists of a microstructured silica fiber taper with collapsed air holes in the waist. The transmission spectra of the taper exhibits a series of interference peaks owing to the beating between several modes of the solid taper waist. The interference peaks shift to longer wavelengths as the temperature increases from 200 C to 1000 C. The sensor exhibits a linear response and can be operated with different wavelengths which makes it attractive for diverse applications.
A large-mode-area holey fiber was tapered to a point in which the airholes collapsed, and its dep... more A large-mode-area holey fiber was tapered to a point in which the airholes collapsed, and its dependence on temperature and strain was studied. The transmission spectrum of such a fiber exhibits a series of peaks owing to the interference between the modes of the solid taper waist. We found that the interference peaks shifted to shorter wavelengths as the taper was elongated. However, the peaks were insensitive to temperature. The fabrication and advantages of our novel wavelength-encoded temperature-independent strain sensor compared with other optical fiber strain sensors are discussed.
The Bi12TiO20-based fiber-optic voltage sensor with optically controlled sensitivity
Fourteenth International Conference on Optical Fiber Sensors, 2000
We report on a fiber optic voltage sensor with optically controlled sensitivity. The sensor opera... more We report on a fiber optic voltage sensor with optically controlled sensitivity. The sensor operates at two widely separated wavelengths (633 nm and 976 nm). one of which is a control signal (976 nm). We have demonstrated experinientally the variation of the sensor's sensitivity from 0.0 1 % to 0 per I Vnns for control power changes in the range of 0 ÷ 7 μW.
Journal of Lightwave Technology, 2017
We present an all-fiber Mach-Zehnder modal interferometer based on a special photonic crystal fib... more We present an all-fiber Mach-Zehnder modal interferometer based on a special photonic crystal fiber taper and its performance as a transducer for biological sensing. The sensor showed refractive index sensitivity around 722.3 nm/RIU for measurements between 1.30864 and 1.32014 RIU. We investigated the interferometer as a transducer for an immunosensor system after immobilization of an antigen over the activated taper waist, where it detected the interaction between antigen and antibody achieving a record detection limit of 125 pg/ml of antibody concentration. This extra low detection limit allows the modal interferometer to be used in biosensing applications, such as disease diagnosis, or in the food industry.
<title>Measurements of changes in transmission spectra of human venous blood as a method for control of low-intensity He-Ne laser biomedical effect</title>
Eighth International Symposium on Laser Metrology, 2005
ABSTRACT We report experimental evidence of light-induced changes in the transmission spectrum of... more ABSTRACT We report experimental evidence of light-induced changes in the transmission spectrum of human venous blood under the action of low-intensity radiation from He-Ne laser. We have applied a sensitive registration technique and the transmission spectra of diluted and nondiluted heparinized human venous blood have been analyzed before, after and in the course of irradiation. When irradiating nondiluted blood, reproducible variations of the blood transmission spectrum in the range of 640 - 805 nm have been observed for the first time. We found these changes correlate with oxygen saturation. The changes in transmission spectra and oxygen saturation of venous blood after 1-3 procedures of irradiation can be used as a method to detect an individual sensitivity to intravenous laser irradiation.
Optical voltage sensing: the influence of photoconductivity on sensor parameters
SPIE Proceedings, 2000
The influence of photoconductivity upon operation of a Bi 12 TiO 20-based optical voltage sensor ... more The influence of photoconductivity upon operation of a Bi 12 TiO 20-based optical voltage sensor is reported. We have demonstrated, that the presence of photoconductivity defines non-uniform sensitivity of the sensor in the cross section of an infrared light beam. The sensitivity of the sensor is shown to depend on the intensity of light as a consequence of photoconductivity of a crystal. An agreement between our theoretical model and experimental results has been demonstrated.
Defocused transfer function for measurement of refractive index profiles of axially symmetric optical fibers
Optical Engineering, 2008
ABSTRACT A defocused transfer function of experimental microscopic bright-field images, closely c... more ABSTRACT A defocused transfer function of experimental microscopic bright-field images, closely connected with the evaluation of the relative refractive index profile of axially symmetric optical fibers, is presented. It is shown that with this function it is possible to obtain, with high precision, the defocused bright-field images of investigated fibers from their focus images and then to easily evaluate the relative refractive index profiles of the fibers. (c) 2008 Society of Photo-Optical Instrumentation Engineers.
Optics Communications, 2001
We report on collective eects for the train of optical pulses when a reproduction of the periodic... more We report on collective eects for the train of optical pulses when a reproduction of the periodical pulse train occurs at some distance in dispersive medium. The reproduction of the initial temporal distribution can be treated as a temporal analog of the spatial Talbot eect. In experiment with a multimode ®ber, the group of seven pulses lost its temporal shape converting in one broad pulse at the distance of 1200 m, while continuous train of pulse preserved its temporal structure.
IEEE Photonics Technology Letters, 2000
We report a new configuration of the fiber-optic voltage sensor based on the Bi 12 TiO 20 crystal... more We report a new configuration of the fiber-optic voltage sensor based on the Bi 12 TiO 20 crystal, which allows simultaneous measurements of both voltage and temperature. In our scheme, a quarter-wave plate, being an inherent element of voltage sensor, serves simultaneously as a phase-shifting element and as a temperature sensitive element. The sensor operates at two wavelengths (633 and 976 nm). The sensor has a linear temperature characteristic within the range of 10 C-70 C, providing the accuracy of temperature measurements of 0.3 C. As a voltage sensor, this device has a linear amplitude characteristic up to 1000 rms and the excellent temperature stability of 0.1% within the temperature range of 10 C.-70 C.
IEEE Photonics Technology Letters, 2000
We describe a fiber optic voltage sensor with optically controlled sensitivity. The sensor operat... more We describe a fiber optic voltage sensor with optically controlled sensitivity. The sensor operates at two widely separated wavelengths (633 and 976 nm), one of which is a control signal (976 nm). We show that at a properly chosen wavelength of the control signal and of the phase-retarding element, variations of the power of the control signal allow increases or decreases in the sensitivity of the sensor. A theoretical analysis of sensitivity as a function of the optical power of a control signal is presented. We have demonstrated experimentally variation of the sensor's sensitivity from 0.01% to 0 per 1 V rms of control power changes in the range of 0-7 W.
Optics Letters, 2006
A large-mode-area holey fiber was tapered to a point in which the airholes collapsed, and its dep... more A large-mode-area holey fiber was tapered to a point in which the airholes collapsed, and its dependence on temperature and strain was studied. The transmission spectrum of such a fiber exhibits a series of peaks owing to the interference between the modes of the solid taper waist. We found that the interference peaks shifted to shorter wavelengths as the taper was elongated. However, the peaks were insensitive to temperature. The fabrication and advantages of our novel wavelength-encoded temperature-independent strain sensor compared with other optical fiber strain sensors are discussed.
Laser Physics Letters, 2014
ABSTRACT The novel, extremely simple to assemble, design of a ~2.05 µm ytterbium–holmium co-doped... more ABSTRACT The novel, extremely simple to assemble, design of a ~2.05 µm ytterbium–holmium co-doped all-fiber laser (YHDFL) oscillating in the gain-switching pulsed regime is reported. The YHDFL is pumped by a 1064 nm ytterbium doped fiber laser, while pulsing at ~2.05 µm, is accomplished using an acousto-optic modulator placed between the two lasers. At the optimal conditions, the YHDFL produces a train of very stable, single per modulation period, pulses, 1 µJ in energy and 1 µs in duration at a 3 dB level, at repetition rates of 50...60 kHz.
A method for monitoring strain induced changes suffered by structure, materials or components usi... more A method for monitoring strain induced changes suffered by structure, materials or components using a single-material microstructured optical fiber tapered by a non-adiabatic process.
Large-mode-area single material holey fiber tapers with collapsed by nonadiabatic process air hol... more Large-mode-area single material holey fiber tapers with collapsed by nonadiabatic process air holes in the waist for fiber optic sensors and a method for manufacturing these tapers are claimed. The gradual collapsing of the holes is achieved by tapering the fibers with a "slow-and-hot" method. This nonadiabatic process makes the fundamental mode of the holey fiber to couple to multiple modes of the solid taper waist. Owing to the beating between the modes, the transmission spectra of the tapered single material holey fibers exhibit several interference peaks. That means the all-fiber Mach-Zehnder type interferometer is formed in a holey fiber such a way. The multiple peaks, combined with a fitting algorithm, allow high-accuracy refractometric measurements, temperatureindependent strain measurements, measurements of high temperature and may be used for measuring many others parameters.
Sensors, Cameras, and Systems for Scientific/Industrial Applications VIII, 2007
Using a simple non-destructive and non-interferometric technique, we obtained an approximation of... more Using a simple non-destructive and non-interferometric technique, we obtained an approximation of the average index profile for a partially symmetrical air-silica microstructured optical fiber. The method proposed in [1] for conventional fibers, where an image of the phase gradients is introduced into a transmitted optical field by a fiber sample, was used. An image of the phase gradients was obtained using a technique based on bright field microscopy. Then, an average of the refractive index profile for optical fibers was reconstructed using the inverse Abel transform.
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Papers by Vladimir Minkovich