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Öğe Controlling Femtosecond Laser Filaments via Quasi-Hermite Gaussian Beam Modes(Polish Acad Sciences Inst Physics, 2022) Kaya, N.; Kaya, G.; Kolomenski, A.; Schuessler, H.We present the possibilities of controlling and organizing femtosecond laser filaments and white-light formation via generating quasi-Hermite Gaussian beam modes in water. The quasi-Hermite Gaussian modes are created as transverse structures with different intensity and phase distributions by modulating the spatial phase front in the incident Gaussian beam. We have created phase masks on a spatial light modulator to produce desired beam profiles such as quasi-Hermite Gaussian beam modes. By creating the quasi-Hermite Gaussian beam modes from the incident Gaussian mode, we have shown that multiple filaments and white-light generation patterns can be controlled and organized depending on the created beam mode profile. Since only one initial beam was employed, the beam and the created side patterns were mutually coherent, which enables their use for pump-probe spectroscopy and other experiments requiring mutual coherence of the beams employed.Öğe Design of a New Ultra-sensitive Methane Sensor Based On Optical Approaches that Utilize Laser Diodes(Old City Publishing, 2021) Keskin, A.; Kaya, N.; Kaya, G.We design a new ultra-sensitive optical methane sensor by combining such optical approaches as appropriate use of absorption bands of methane by HITRAN database in the near-infrared (NIR) region, effective absorption path length in circular multi-pass optical cell, a wavelength modulation, and noise suppression with dual beam configuration. The design offers a compact and portable optical sensor for methane gas measurements in real time and high sensitivity. In the design, one can select different laser diode source to expand the selectivity labels for the interest many other trace gases. This is inexpensive and simpler experimental design without complexity of laser frequency locking and phase stabilization. It can find wide applications in many fields such as physical, environmental, and atmospheric research as well as physics, analytical chemistry, biology, medical diagnosis and process technology. © 2021 Old City Publishing, Inc.Öğe Spatio-temporal control of femtosecond laser filamentation and white-light generation(American Institute of Physics Inc., 2017) Kaya, N.; Kaya, G.; Strohaber, J.; Kolomenskii, A.; Schuessler, H.Several possibilities are investigated to control spatio-temporal characteristics of the femtosecond filamentation process and the resulting white-light generation. We controlled the development of self-focusing, and resulting locations of filaments producing white-light in water by changing the transverse spatial phase of an initial Gaussian beam with a computer generated holographic technique and a spatial light modulator. We studied intense femtosecond filamentation and propagation of femtosecond pulses with different transverse modes in water. The filament propagation length was found to increase with Bessel-Gaussian modes of the beams, when more lateral lobes were used, under the conditions of the same peak intensity, pulse duration, and size of the central peak of the incident beam. We also investigated variations of white-light generation when the delay between the two pulses was varied. With a decrease of the relative delay, an enhancement of white-light output was observed, which at near-zero delays was reverted to a suppression of white-light generation. © 2017 Author(s).Öğe Time slicing in 3D momentum imaging of the hydrogen molecular ion photo-fragmentation(Amer Inst Physics, 2017) Kaya, N.; Kaya, G.; Pham, F. V.; Strohaber, J.; Kolomenskii, A. A.; Schuessler, H. A.Photo-fragmentation of the hydrogen molecular ion was investigated with 800 nm, 50 fs laser pulses by employing a time slicing 3D imaging technique that enables the simultaneous measurement of all three momentum components which are linearly related with the pixel position and slicing time. This is done for each individual product particle arriving at the detector. This mode of detection allows us to directly measure the three-dimensional fragment momentum vector distribution without having to rely on mathematical reconstruction methods, which additionally require the investigated system to be cylindrically symmetric. We experimentally reconstruct the laser-induced photo-fragmentation of the hydrogen molecular ion. In previous experiments, neutral molecules were used as a target, but in this work, performed with molecular ions, the initial vibrational level populations are well-defined after electron bombardment, which facilitates the interpretation. We show that the employed time-slicing technique allows us to register the fragment momentum distribution that reflects the initial molecular states with greater detail, revealing features that were concealed in the full time-integrated distribution on the detector. Published by AIP Publishing.
