Abstract-µJ-level multi-cycle terahertz generation in a periodically poled Rb:KTP crystal

 

Wenlong Tian, Giovanni Cirmi, Halil T. Olgun, Patrick Mutter, Carlota Canalias, Andrius Zukauskas, Lu Wang, Elias Kueny, Frederike Ahr, Anne-Laure Calendron, Fabian Reichert, Kore Hasse, Yi Hua, Damian N. Schimpf, Hüseyin Çankaya, Mikhail Pergament, Michael Hemmer, Nicholas Matlis, Valdas Pasiskevicius, Fredrik Laurell, Franz X. Kärtner

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-46-4-741

We demonstrate multi-cycle terahertz (MC-THz) generation in a 15.5 mm long periodically poled rubidium (Rb)-doped potassium titanyl phosphate (Rb:PPKTP) crystal with a poling period of 300 µm. By cryogenically cooling the crystal to 77 K, up to 0.72 µJ terahertz energy is obtained at a frequency of 0.5 THz with a 3 GHz bandwidth. A maximum internal optical-to-terahertz conversion efficiency of 0.16% is achieved, which is comparable with results achieved using periodically poled lithium niobate crystal. Neither photorefractive effects nor damage was observed with up to 900mJ/cm2$900{\mathrm{m}\mathrm{J}/\mathrm{c}\mathrm{m}}^2$, showing the great potential of Rb:PPKTP for multi-millijoule-level MC-THz generation.

© 2021 Optical Society of America

Abstract-Segmented terahertz electron accelerator and manipulator (STEAM)

Dongfang Zhang, Arya Fallahi, Michael Hemmer, Xiaojun Wu, Moein Fakhari, Yi Hua, Huseyin Cankaya, Anne-Laure Calendron, Luis E. Zapata, Nicholas H. Matlis, Franz X. Kärtner

https://www.nature.com/articles/s41566-018-0138-z

Acceleration and manipulation of electron bunches underlie most electron and X-ray devices used for ultrafast imaging and spectroscopy. New terahertz-driven concepts offer orders-of-magnitude improvements in field strengths, field gradients, laser synchronization and compactness relative to conventional radiofrequency devices, enabling shorter electron bunches and higher resolution with less infrastructure while maintaining high charge capacities (pC), repetition rates (kHz) and stability. We present a segmented terahertz electron accelerator and manipulator (STEAM) capable of performing multiple high-field operations on the six-dimensional phase space of ultrashort electron bunches. With this single device, powered by few-microjoule, single-cycle, 0.3 THz pulses, we demonstrate record terahertz acceleration of >30 keV, streaking with <10 fs resolution, focusing with >2 kT m–1 strength, compression to ~100 fs as well as real-time switching between these modes of operation. The STEAM device demonstrates the feasibility of terahertz-based electron accelerators, manipulators and diagnostic tools, enabling science beyond current resolution frontiers with transformative impact.

Abstract-Cascaded parametric amplification for highly efficient terahertz generation

Cascaded parametric amplification for highly efficient terahertz generation

https://www.osapublishing.org/ol/abstract.cfm?uri=ol-41-16-3806

Koustuban Ravi, Michael Hemmer, Giovanni Cirmi, Fabian Reichert, Damian N. Schimpf, Oliver D. Mücke, and Franz X. Kärtne

A highly efficient, practical approach to high-energy multi-cycle terahertz (THz) generation based on spectrally cascaded optical parametric amplification (THz-COPA) is introduced. Feasible designs are presented that enable the THz wave, initially generated by difference frequency generation between a narrowband optical pump and optical seed (0.1–10% of pump energy), to self-start a cascaded (or repeated) energy downconversion of pump photons in a single pass through a single crystal. In cryogenically cooled, periodically poled lithium niobate, unprecedented energy conversion efficiencies >8%achievable with existing pump laser technology are predicted using realistic simulations. The calculations account for cascading effects, absorption, dispersion, and laser-induced damage. Due to the simultaneous, couplednonlinear evolution of multiple phase-matched three-wave mixing processes, THz-COPA exhibits physics distinctly different from conventional three-wave mixing parametric amplifiers. This, in turn, governs optimal phase-matching conditions, evolution of optical spectra, and limitations of the nonlinear process. Circumventing these limitations is shown to yield conversion efficiencies ≫10%.

© 2016 Optical Society of America

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