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Phonon-polaritons

Phonon-polaritons are electromagnetic waves coupled to lattice vibrational modes in the THz frequency range in ferroelectric crystals where the mixed EM/lattice vibration waves travel at light-like speeds. We are able to generate, detect, and visualize the motions of polariton waves on a single chip at picosecond time scales through real-space imaging. We are further able to fabricate EM wave devices with specific structures and control the motions of the polaritons. The movies below are demontrations of generation, detection, and control of phonon polaritons. For more information, please read the references below or contact Team Polaritonics.

Movie 1. Broadband THz phonon-polariton generation in an unpatterned LiNbO3 waveguide slab.

Movie 2. Diffraction off a grating.

Movie 3. Single-slit diffraction.

Movie 4. Double-slit diffraction.

Movie 5. Five-slit diffraction.

Movie 6. Y-coupler.

Movie 7. Focusing of ring-excited THz using an axicon.

Movie 8. THz field enhancement using a gold antenna.

Movie 9. THz propagation in a laser machined photonic crystal.

Movie 10. THz focusing using a Luneburg lens.

 

References

1. "Time-resolved imaging of near-fields in THz antennas and direct quantitative measurement of field enhancement," C. A. Werley, K. Fan, A. C. Strikwerda, S. M. Teo, X. Zhang, R. D. Averitt, and K. A. Nelson, Opt. Express 20, 8551-8567 (2012). [url]

2. "Direct visualization of terahertz electromagnetic waves in classic experimental geometries," C. A. Werley, C. R. Tait, and K. A. Nelson, Am. J. Phys. 80, 72-81 (2012). [url]

3. "Comparison of phase-sensitive imaging techniques for studying terahertz waves in structured LiNbO3", C.A. Werley, Q. Wu, K.-H. Lin, C.R. Tait, A. Dorn, and K.A. Nelson, J. Opt. Soc. Am. B 27, No. 11, 2350 (2010). [url]

4. "Terahertz Polaritonics," T. Feurer, N.S. Stoyanov, D.W. Ward, J.C. Vaughan, E.R. Statz, and K.A. Nelson, Annu. Rev. Mater. Res. 37, 317-350 (2007). [url]

Shock studies

Shock waves are of interest in the study of primary traumatic brain injury, material failure, nonlinear acoustic wave propagation, and discovery and generation of exotic states of matter. We use an all-optical table-top experimental approach to generate shock waves in a quasi-two-dimensional geometry. A laser focused to a ring generates a converging shock wave travelling laterally along the sample plane through thermal expansion and ablation of the sample. The converging shock increases in pressure as the wave approaches the center of convergence, allowing for pressures as high as tens of gigapascals to be readily achieved. For more information, please see the references below or contact Team Extreme Conditions.

 

Movie 1. Shock wave-induced fracture of a potassium sulfrate crystal embedded in a polystyrene matrix. Laser ring excitation diameter 170 micrometers, 2.0 mJ laser pulse energy, pressure at shock focus approximately 6.5 GPa.

Movie 2. Surface acoustic wave-induced fracture on an aluminum mirror sufrace. Laser ring excitation diameter 170 micrometers, 0.1 mJ laser excitation pulse energy. 

References: 

1. Veysset, David, et al. "Laser-induced versus shock wave induced transformation of highly ordered pyrolytic graphite." Applied Physics Letters 106.16 (2015).

2. Veysset, David, et al. "Glass fracture by focusing of laser-generated nanosecond surface acoustic waves." Scripta Materialia 158 (2019): 42-45.

3. Pezeril, Thomas, et al. "Direct visualization of laser-driven focusing shock waves." Physical review letters 106.21 (2011): 214503.

LIPIT

We use an all-optical table-top approach to accelerate microparticles to supersonic velocities to conduct impact testing. This experimental technique, the laser-induced particle impact test (LIPIT), probes extremely high-strain-rate mechanics with high reproducibility and in-situ imaging. These data can be used to extract high-strain-rate material properties to then inform material development and simulations. For more information, please read the references below or contact Team Extreme Conditions.

Movie 1. SEBS Oleogel impacted by Steel particle at 630 m/s resulting in 150 um penetration into the gel. Collaboration with ARL.

Movie 2. Poly-crystalline Alumina Cantilever impacted by Silica particle at 78 m/s resulting in cantilever fracture and particle rebound at 23 m/s. Collaboration with Todd group, Oxford University.

Movie 3. Aluminum impacted by Aluminum particle at 805 m/s resulting in bonding with associated jetting. Collaboration with Schuh group, MIT.

Movie 4. Aluminum impacted by Aluminum particle at 605 m/s resulting in rebound at 45 m/s and no jetting. Collaboration with Schuh group, MIT.

Movie 5. Carbon 3D-lattice impacted by Silica particle at 240 m/s resulting in rebound at 50 m/s and material ejection. Collaboration with Portela group, MIT.

References

1. "High-Strain-Rate Behavior of a Viscoelastic Gel Under High-Velocity Microparticle Impact," D. Veysset, Y. Sun, J. Lem, S. E. Kooi, A. A. Maznev, S. T. Cole, R. A. Mrozek, J. L. Lenhart, K. A. Nelson, Exp. Mech. 60, 1179-1186 (2020). [url]

2. “In-situ observations of single micro-particle impact bonding,” M. Hassani-Gangaraj, D. Veysset, K. A. Nelson, and C. A. Schuh, Scripta Materialia 145, 9-13 (2018). [url]