Nonlinear optics revolutionized the ability to create directed, laser-like light particularly in the regions where lasers based on conventional population inversion are not practical. New breakthroughs in attosecond extreme nonlinear optics promise a similar revolution in the X-ray regime.
In this talk, I will discuss the fundamental quantum physics and the phase matching limits of high order harmonic generation in the context of creating coherent X-ray waveforms in the soft X-ray region that can be tailored at the moment of generation. Such a versatile designer light is ideal for 4D studies of various bio- and nano-materials systems with attosecond temporal and nanometer spatial resolution, as well as with element specificity. I will also discuss the path forward for generating bright coherent X-ray beams from a laboratory-scale apparatus at photon energies of 10 keV and greater with unprecedented attosecond-to-zeptosecond pulse durations, and with arbitrary spectral, temporal shapes, and polarization states. A fully spatially and temporally coherent version of the Roentgen X-ray tube with exquisite quantum control of the properties of the soft and hard X-ray light may be possible.
1. T. Popmintchev, et al., Nature Photonics 4, 822 (2010); Science 336, 1287 (2012).
2. D. Popmintchev, et al., Science 350, 1225 (2015).
3. T. Fan, et al., PNAS 112, 14206 (2015).
We show that it is possible to use of a train of counterpropagating light pulses to enhance
the coherent upconversion of intense femtosecond lasers into the extreme ultraviolet (EUV)
region of the spectrum. This all optical quasi-phase-matching uses interfering beams to
scramble the quantum phase of the generated EUV light, suppressing the contribution of
out-of-phase emission. Selective enhancement of up to 600X is observed at photon energies
of ~70 eV using argon gas and ~ 150 eV using helium gas.
A new approach for design of resonators of diode-pumped solid state lasers is presented. The required beam waist radii in both the active medium and the passive mode-locking element as well as the operational point on the resonator stability diagram are the initial parameters of our analysis. Analytical formulae are derived for calculation of 3- and 4-mirror resonators.
It is shown that a combination of a polarizer, a type II second harmonic generation (SHG) crystal at nearly phase- matched conditions, and a back reflector has pulse shortening and mode-locking capabilities. The latter are due to the intensity dependent change of the polarization state of the fundamental wave by cascade second-order processes in the nonlinear crystal. This change of polarization state causes nonlinear reflection, when the fundamental wave passes back through the polarizer, i.e. the combination of a polarizer a SHG crystal and a dielectric mirror acts for the fundamental wave as a nonlinear mirror, called by us a frequency doubling polarization mirror (FDPM). The dependence of the properties of the FDPM on the nonlinear characteristics and the orientation of the SHG crystal, as well as on the accumulated phase shift between the second harmonic and the fundamental wave within the space between the nonlinear crystal and the back reflector were investigated.
A new method for restoration of ceramic surfaces, based on laser ablation of impurities has been developed. Optical pulses generated by Nd:YAG laser are used to remove a high absorbing layer (fungi) from the surface of a lower absorbing ceramic substrate. Two regimes of operation have been employed: Q-switched mode and free running mode. Analysis suggests that Q-switched mode of operation is the most efficient for cleaning processes. Densities of energy 1.60 - 1.90 J/cm2 at the fundamental wave and pulse duration 10 ns are the typical values for removing of impurities of fungi from ceramic surfaces. The second, third and forth harmonics of the Nd:YAG laser have been also used for optimization of the process of laser restoration. The absence of structural changes of the ceramics surface after the process of laser cleaning has been observed by X-ray analysis. The used ceramic substrate is dated 5000 BC- a part of the excavations near Durankulak.
Conference Committee Involvement (1)
X-Ray Lasers and Coherent X-Ray Sources: Development and Applications XIII
12 August 2019 | San Diego, California, United States
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