The method based on the application of integrating spheres and a movable sample for measurements of scattering and absorption coefficients of transparent and turbid media was implemented for the investigation of optical properties of different organosilicone polymers used in fiber optics, including polysiloxanes doped with metal powder. For the determination of the optical absorption and scattering coefficients together with the scattering anisotropy of polymers basing on the experimental data, the inverse problem of the radiation transfer theory was implemented using two approaches: Monte-Carlo simulation and an analytical solution in the single-scattering approximation.
We present a technique for measurement of the intensity profile of high-power laser beams. It is based on the application of a matrix of the copper-coated optical fibers. Laser radiation propagating through a copper-coated optical fiber is partially scattered and subsequently absorbed by the copper layer. The change of an electrical resistance of the copper coating caused by its heating is measured by an ohmmeter. It is estimated that this method allows measurements of the intensity profile of laser beams with an average power exceeding 10 kW level. The optical intensity profile and the angle of divergence of the single-mode laser beam were measured using the proposed technique.
In this paper we introduce a novel approach for the measurement of the intensity profile of high-power laser radiation, which does not require any preliminary attenuation. It is based on the application of the matrix made of multimode passive copper-coated optical fibers. It is well known, that laser radiation experiences Rayleigh and Mie scattering while transmitting along an optical fiber. Radiation scattered inside the fiber core is completely absorbed by the outer copper layer leading to its heating. The temperature change of the metal coating proportional to the transmitted optical power is determined directly by measuring its electrical resistance. A matrix sensor was assembled for measuring the transverse intensity distribution of the laser beams. It comprised nineteen 660 μm (core diameter 600 μm) multimode copper-coated optical fibers. Intensity profile measurements were carried out for the 67 W single-mode Yb-doped fiber laser and 72 W multimode laser diode sources. The laser radiation was directed into the polished end faces of the fiber matrix elements. Optical power transmitted through each fiber was proportional to the incident optical intensity at corresponding location of the fiber end face. The transverse intensity profile of the laser beam was evaluated by measuring the resistance change of the copper coating of each fiber. Preliminary the calibration of the resistance dependence on the incident optical power was separately conducted for all 19 fibers. An introduced technique can be also applied for the determination of the radiation beam quality factors such as M2 and BPP.
A novel method for high-sensitive measurements of optical attenuation in metal-coated optical fibers in a wide range of wavelengths is demonstrated. Some part of the radiation transmitted through the waveguiding core of the metallized silica fiber is scattered and eventually absorbed in the carbon layer or the metal coating, thus heating it. Absorption in the silica core also contributes to the overall fiber heating. The method used for determination of optical attenuation coefficients of metallized fibers is based on the measurement of the change of temperature-dependent electrical resistance of metal coating induced by transmitted laser radiation. A number of single-mode and multimode metallized fibers with different geometry were investigated using several laser sources operating in visible and near infrared ranges. Experimentally obtained spectral dependence of optical losses of copper-coated fibers was analyzed. Possible explanations for optical attenuation mechanisms at different wavelengths and in different fibers were proposed. The obtained results can help to optimize various devices based on metal-coated fibers, such as laser radiation power fiber sensors or high-power laser sources.
A technique for measurements of output power of fiber lasers using a metal-coated fiber sensor is proposed. Optical radiation transmitting through the core of a copper-coated silica fiber is partially scattered and, therefore, absorbed in the copper layer. The change of an electrical resistance of the metal coating induced by its heating is measured. This technique can be used for the real-time measurement of output radiation power of fiber laser sources. The measurement range of optical power can be controlled by changing the bend curve radius of the metal-coated fiber. Optical scattering coefficients of the metal-coated fiber core were determined using the proposed theoretical model of the fiber sensor heating.
A method for high-sensitive measurement of optical power of fiber lasers is introduced. It is based on application of a metal-coated fiber as a sensor. A part of optical radiation transmitting through the core of a metal-coated silica fiber is scattered and further absorbed in the outer cladding. The change of electrical resistance of the metal coating induced by its heating is measured. This technique can be used for measurements of the output power of fiber laser sources in real time with minor optical losses and beam distortion. The dynamic range can be widely varied by changing the bend curve radius of the sensor fiber. Optical scattering and bend losses were investigated for different geometries of metal-coated fibers. A heating model of metal-coated fibers was developed.
Laser radiation scattering in copper-coated silica fibers was investigated by measuring electrical resistance of the metal layer. Scattering coefficients were determined using theoretical model of fiber heating induced by absorption of scattered radiation in the coating. This method can be adopted for direct measurement of fiber laser radiation power.
Optical transmission spectra of polysiloxane polymers used in fiber optics were investigated. Temperature dependences of the polymer absorption coefficients at pump and generation wavelengths of Yb-doped laser were measured by means of laser calorimetry. Thermal regime of the commercial fiber unit under laser generation conditions was investigated.
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