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Gigantic optical nonlinearity: laser-induced change of dielectric permittivity of the order of unity Guohua Zhu, John K. Kitur, Lei Gu, Jarrett Vella, Augustine Urbas, Evgenii E. Narimanov, and Mikhail A. Noginov ACS Photonics, Just Accepted Manuscript • DOI: 10.1021/acsphotonics.5b00009 • Publication Date (Web): 31 Mar 2015 Downloaded from http://pubs.acs.org on April 4, 2015
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Gigantic optical nonlinearity: laser-induced change of dielectric permittivity of the order of unity Guohua. Zhu,1 John. K. Kitur,1 Lei Gu,1 Jarrett. Vella,2,3 Augustine. Urbas,4 Evgenii. E. Narimanov,5 and Mikhail. A. Noginov1,* 1 Center for Materials Research, Norfolk State University, Norfolk, VA 23504, USA. 2 Sensors Directorate, Wright-Patterson Air Force Base, OH 45433, USA. 3 Wyle, Dayton, OH 45431, USA. 4 Materials and Manufacturing Directorate, Wright-Patterson Air Force Base, OH 45433, USA. 5 Birck Nanotechnology Center, Department of Electrical and Computer Engineering, Purdue University, West Lafayette, IN 47907, USA.
Keywords: Nonlinear optics, Optical materials, Kerr effect, Dispersion, Metamaterials. Abstract: A possibility to tune optical properties of materials on demand is of great importance to both fundamental science and applications. We show that nanosecond laser pumping can significantly depopulate the ground state of AF455 dye nanoparticles, resulting in gigantic change of dielectric permittivity of the order of unity. Such extreme nonlinearity (χ(3)=1.3x10-5 esu), evidenced by increase of the Mie scattering efficiency, places AF455 dye among the most efficient χ(3) nonlinear optical materials, extends the limits of active metamaterials and plasmonics, and paves the way to ultimate control of photonic devices and systems.
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Two classes of materials most commonly used in optics and photonics are low-loss dielectrics (including semiconductors) and metals. Their distinctly different optical properties, e.g. ability or inability to propagate light waves, are determined by their dielectric permittivities, ε˜ =ε’+iε”, whose real parts are positive in dielectrics, ε’>0, and negative in metals, ε’1, although, the switching rates typically do not exceed 100 Hz. (Here and below, n˜ =n+ik.) Tuning via mechanical
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reconfiguration of the metamaterial is usually slow too [13]. However, 1 MHz switching rate has been reported in [14]. The second category of tuning mechanisms includes laser induced nonlinearities [15,16], saturable and reverse saturable absorption [16], modification of dispersion determined by transient optical gain [8,17,18], and fast laser-induced phase transitions (in chalcogenide glasses) [19]. The characteristic times of such processes range from sub-picosecond to 100 nanoseconds. However, the changes of | ε˜ |, | µ˜ | and | n˜ | are typically small, between ~0.001 and ~0.1. (Note that femtosecond laser-induced increase of electric conductivity of silica by 18 orders of magnitude, to reach that of semiconductors, has been reported in Ref. [20], and the ~100 fs laser induced phase transition in VO2 has been reported in Ref. [21]. To the best of our knowledge, these processes have not been utilized in tunable metamaterials yet.) Remarkably,
strong
control
of
plasmon
and
metamaterial
responses,
|∆ ε˜ MM|~|∆ µ˜ MM|~|∆ n˜ MM|~1, can be achieved at much smaller changes of dielectric permittivity of interfacing constituent materials, 0.0010, to a metallic state, ε’
