Search academic texts

Information × Registration Number 0218U001238, 0117U001862 , R & D reports Title Laser femtosecond filaments in isotropic and anisotropic media:fundamental and applied aspects. popup.stage_title Head Blonskyi Ivan Vasylyovych, Registration Date 26-01-2018 Organization Institute of physics NASU popup.description2 The object of study: crystal silicon, vitreous chalcogenide semiconductors. Objective: The project aims to study the mechanisms of interaction of ultrashort light pulses with matter and their applications. The aim is to find common patterns of spatio-temporal and spectral transformation of high intensity optical pulses of femtosecond duration in their propagation in transparent Kerr media in filamentation regime and structural changes induced by femtosecond laser pulses in optical engineering materials. Research Methods: The measurement of spectral and spatial, luminescent, polarization and temporal properties of femtosecond laser pulses in filamented mode. Experimental study of the dynamics of filamentation and the spectral transformation of femtosecond laser pulses of the infrared band with a wavelength of 1.55 ?m in crystalline silicon and vitreous chalcogenide semiconductors was carried out. For the first time, an experimental setup of time-resolved microscopy was created, which allows direct measurements of the space-time distribution of femtosecond laser pulses with a wavelength of 1.55 ?m propagating in optical materials of the infrared range. Using the created experimental setup, the peculiarities of the spatial and temporal transformation of the femtosecond laser pulses during their propagation in c-Si as well as the properties of the plasma channel formed as a result of the two-photon absorption of excitation radiation in this semiconductor and in As2S3 were determined. It is shown that the formation of a picture of nonstationary transmission in crystalline silicon is determined by contributions of a plasma induced and Kerr change of the refractive index and also by two-photon absorption under the action of a femtosecond excitation pulse. It was established that the nonlinear interaction of femtosecond laser radiation with the material leads to the expansion of the spectral band of the femtosecond excitation pulses as well as to the generation of the visible radiation of the third harmonic at a wavelength of 0.515 microns in c-Si and As2S3. It is shown that the contribution of the Kerr mechanism to general phase modulation far exceeds the contribution of the plasma mechanism. For the first time, the generation of intense visible radiation of the third harmonic at a wavelength of 0.517 microns in crystalline silicon and As2S3 was observed and its angular distribution was investigated. Structural transformations of a material induced by femtosecond laser pulses of the infrared range in crystalline silicon and chalcogenide glass were studied. The creation of optical waveguides in c-Si volume with a femtosecond laser of 1.5 ?m wavelength is demonstrated. This is the first report of a 3D-controlled sub-surface modification of c-Si using femtosecond laser pulses, as well as the first demonstration of optical waveguides recorded in c-Si with ultra-short laser pulses. Based on the results of characterization of waveguides, it is found that the refractive index difference in the waveguide and in the unmodified crystal is equal to 6 ? 10-4 and 3.5 ? 10-4, respectively. The diameter of the waveguide is 20 ?m according to the measurement results. In this way, multi-level arrays of functional waveguides in c-Si can be created. With subsequent optimization of laser parameters and scanning, it will be possible to create additional integrated optical elements of different architecture with refractive index modulation control. The new laser recording method has prospects to be used in integrated 3D optics, silicon photonics and optical communication between chips. The results obtained during the work will be used to improve the methodological basis of the Center for the collective use of "Laser femtosecond center" at the Institute of Physics of the National Academy of Sciences of Ukraine, as well as in the educational process of students and postgraduates of physical specialties. The installation of time-resolved microscopy of the IR range will be used to conduct research on non-linear optical properties of structural infrared materials. Experimental data on the spatial-temporal transformation of femtosecond laser pulses of the IR range when propagated in crystalline silicon should be taken into account when developing the technology of femtosecond laser modification of these optical materials. The discovered phenomenon of efficient generation of the third harmonic of femtosecond laser radiation at a wavelength of 1.55 microns in crystalline silicon can be used in the development of laser radiation converters. Scope: modification of the properties of optoelectronics materials. Product Description popup.authors Блонський Іван Васильович Головченко Олена Миколаївна Кадан Віктор Миколайович Коренюк Петро Іванович Рибак Андрій Станіславович popup.nrat_date 2020-04-02 Close