Overcoming the absorption limit in high-harmonic generation from crystals

Hanzhe Liu; Giulio Vampa; Jingyuan Linda Zhang; Yu Shi; Siddharth Buddhiraju; Shanhui Fan; Jelena Vuckovic; Philip H. Bucksbaum; David A. Reis

arXiv · 1905.02821

Overcoming the absorption limit in high-harmonic generation from crystals

Hanzhe Liu·Giulio Vampa·Jingyuan Linda Zhang·Yu Shi·Siddharth Buddhiraju·Shanhui Fan·Jelena Vuckovic·Philip H. Bucksbaum·David A. Reis

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Abstract

Since the new millennium coherent extreme ultra-violet and soft x-ray radiation has revolutionized the understanding of dynamical physical, chemical and biological systems at the electron's natural timescale. Unfortunately, coherent laser-based upconversion of infrared photons to vacuum-ultraviolet and soft x-ray high-order harmonics in gaseous, liquid and solid targets is notoriously inefficient. In dense nonlinear media, the limiting factor is strong re-absorption of the generated high-energy photons. Here we overcome this limitation by allowing high-order harmonics generated from a periodic array of thin one-dimensional crystalline silicon ridge waveguides to propagate in the vacuum gaps between the ridges, thereby avoiding the high absorption loss of the bulk nonlinear material and resulting in a ~ 100-fold increase in propagation length. As the grating period is varied, each high-harmonic shows a different and marked modulation, indicating the onset of coherent addition which is otherwise suppressed in absorption-limited emission. By beating the absorption limit, our results pave the way for bright coherent short-wavelength sources and their implementation in nano-photonic devices.

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Hanzhe Liu, Giulio Vampa, Jingyuan Linda Zhang, Yu Shi, Siddharth Buddhiraju, Shanhui Fan, Jelena Vuckovic, Philip H. Bucksbaum, David A. Reis. 2019-05-07. Overcoming the absorption limit in high-harmonic generation from crystals. https://arxiv.org/abs/1905.02821

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