Four-Wave Mixing of Extreme-UV Pulsewith Rare Gas Ion

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Important Dates

Conference:

Aug. 18-20, 2018

Full Paper Due: Jul. 20, 2018

Abstract Due: Jul. 20, 2018

Audience Registration Due:
Aug. 18, 2018

Presentations of The Int'l Symposium on Photonics and Optoelectronics (SOPO 2016)

● Four-Wave Mixing of Extreme-UV Pulsewith Rare Gas Ion
Author(s)
Hsuhsin Chu
Affiliation(s)
National Central University
KEYWORDS
Extreme-UV
ABSTRACT
In the past decades, several kinds of coherent extreme-UV (EUV)/x-ray sources have been developed with ultrashortdurations and ultrahigh intensities, such as x-ray free electron laser and high-harmonic generation (HHG). Therefore, it is possible to explore the science of EUV/x-ray nonlinear optics now. There are severalEUV/x-ray nonlinear interactions have been demonstrated. For example, non-collinear wave mixing of EUV andoptical pulses is obtained in high-harmonic generation process [1]. Four-wavemixing with EUVtransient gratings on SiO2 [2], x-ray/optical sum-frequency generation in diamond [3], and x-ray second harmonicgeneration in diamond [4] have been achieved by using EUV/x-ray free electron lasers. In these experiments, the measured conversion efficiency range from 10−11 to 10−7. In this presentation, we propose to use rare gas ions as the interacting medium, which canbe prepared by using an intense near-IR (NIR) pulse focused onto a rare gas jet. The intense NIR pulse ionizes thegas atoms to a proper ionization stage through optical-field ionization at its front edge, then mixes with the followingEUV pulse by the ions. If the ionization potentials of the remaining electrons in the ion are larger than the EUVphoton energy, photoionization will not occur and absorption of the EUV pulse can be greatly reduced. However, theremaining electrons can still provide the required response for nonlinear wave mixing. Insuch kind of isotropic system, third-order nonlinearity is the dominant nonlinearresponse. Therefore, we plan to demonstrate the four-wave mixing(FWM) of one EUV photon and two NIR photons. We numerically calculatethe third-order nonlinear polarizability of Ar3+ ions with the combinationof R. D. Cowan’s Atomic Structure Code [5] and Wigner-Eckart theorem. As a result of that the ionization potential of the forth electron of Ar is 59.81 eV, the Ar3+ ion canbe used for the EUV waves with wavelengths longer than 20.7 nm. Thecalculation result ranges from 10−65 to 10−61 coul-m4/volt3 for the interaction of one EUV(30–45 nm) photon and two NIR (810 nm) photons. Then, we propose an experimentwith a 1-μJ EUV pulse (45 nm) and a 50-mJ NIR (810 nm) pulse mixed in a2-mm Ar gas jet. The expected FWM output (40.5 nm) is about 1 nJ, corresponding toa conversion efficiency of 10−3. As a result of thatthe technique of NIR pulse waveform control is well-developed, it can be transferred to EUV pulse though theproposed FWM process. Therefore, this would not only be a demonstration of EUV wave mixing, but also be a newmethod of EUV waveform control.