December 2016
Spotlight Summary by Ilya Shadrivov
Terahertz saturable absorption in superconducting metamaterials
Terahertz frequency range still remains the least explored part of the electromagnetic spectrum; however, this is being rapidly rectified by the research community. As an example, in the past several years we have seen a surge in the development of high power terahertz sources, while the authors of this work develop saturable absorber that reduces its absorption of terahertz waves with increase of the incident power. In optics, saturable absorbers are extremely important components that are used in laser cavities for generation of short pulses.
Here, Keiser and co-authors have made a saturable terahertz absorber by creating a metamaterial from a high-temperature superconductor. The metamaterial elements in the form of split ring resonators are etched in the 100 nm thick YBa2Cu3O7 film and cooled down to 10 K. Then the authors experimentally studied the performance of this absorber with changing temperature and with changing power of the terahertz radiation. By increasing the temperature by 60 K they observed the decrease of absorption from 80% to 20%, while by changing the intensity in the available range, they reduced the absorption from 70% to 40%. The authors explained the observed behavior using a two-fluid model. The dependence of the electromagnetic properties of materials on the intensity of waves is at the essence of nonlinear optics, and this work makes an important contribution to nonlinear physics at terahertz frequencies.
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Here, Keiser and co-authors have made a saturable terahertz absorber by creating a metamaterial from a high-temperature superconductor. The metamaterial elements in the form of split ring resonators are etched in the 100 nm thick YBa2Cu3O7 film and cooled down to 10 K. Then the authors experimentally studied the performance of this absorber with changing temperature and with changing power of the terahertz radiation. By increasing the temperature by 60 K they observed the decrease of absorption from 80% to 20%, while by changing the intensity in the available range, they reduced the absorption from 70% to 40%. The authors explained the observed behavior using a two-fluid model. The dependence of the electromagnetic properties of materials on the intensity of waves is at the essence of nonlinear optics, and this work makes an important contribution to nonlinear physics at terahertz frequencies.
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Article Information
Terahertz saturable absorption in superconducting metamaterials
George R. Keiser, Jingdi Zhang, Xiaoguang Zhao, Xin Zhang, and Richard D. Averitt
J. Opt. Soc. Am. B 33(12) 2649-2655 (2016) View: Abstract | HTML | PDF