CALIFORNIA INSTITUTE OF TECHNOLOGY Ultrafast Terahertz Kerr Effect

CALIFORNIA INSTITUTE OF TECHNOLOGY Ultrafast Terahertz Kerr Effect Spectroscopy of Aromatic Liquids Ian Finneran, Marco Allodi, Geoffrey Blake California Institute of Technology

The Kerr Effect is over 100 years old! DC Kerr Effect ~ms-ns Optical (AC) Kerr Effect ~fs E +V n n n = n 0 + Δn Δn ∝ E 2 1875 John Kerr 1963 Mayer, Gires, Maker, Terhune, Savage

The Kerr Effect is Useful for Chemistry Dynamic Kerr Effect (<0. 1 THz) Optical Kerr Effect (~375 THz) H 2 O Beevers, M. S. , et al. Journal of the Chemical Society, Faraday Transactions 2: Molecular and Chemical Physics (1976) Bartolini, Paolo, et al. Springer 2008. 73 -127.

The intermediate response is not fully understood Short Response (Electronic) Long Response (Collective Reorientation) Intermediate Response

Nonlinear THz spectroscopy is very difficult! Electronics Sizov, Fedir F. , et al. Optical Engineering 52. 3 (2013) Lasers (Photonics)

Terahertz Kerr Effect: Nelson Lab 2009 Picosecond dynamics E n n = n + Δn Δn ∝ E 2 Hoffmann, Matthias C. , et al. "Terahertz Kerr effect. " Applied Physics Letters 95. 23 (2009): 231105.

Terahertz Kerr Effect: Nelson Lab 2009 Hoffmann, Matthias C. , et al. "Terahertz Kerr effect. " Applied Physics Letters 95. 23 (2009): 231105.

THz Kerr Effect - Experimental Setup REGENERATIVE AMPLIFIER (Coherent Legend) Ti: S 800 nm 1 k. Hz >4 m. J 35 fs = 1450 nm = 800 nm = THz fs Ti: Sa OSCILLATOR Ti: S 80 MHz ~ 5 n. J DSTMS THz EMITTER B. S. 85: 15 OPA Signal 1450 nm 400 μJ DETECTION DELAY LINE OPTICAL BEAM BLOCK POL LENS SAMPLE DETECTION PHOTODIODE λ/4 WOLLASTON PRISM Allodi, Finneran, & Blake, 2015 under review.

THz Kerr Effect - Experimental Setup DSTMS THz EMITTER OPTICAL BEAM BLOCK WIRE-GRID POLARIZER POL λ/ 2 LENS SAMPLE DETECTION PHOTODIODES λ/ 4 WOLLASTON PRISM Allodi, Finneran, & Blake, 2015 under review. Image Credits: Rainbowphotonics. com

Electronic Orientational

The Instrument Response is over after 2 ps Probe Pulse = ~40 fs

The Orientational Response is Dependent on Structure

Intermediate Response is clear near 5 ps

Hexafluorobenzene: a double exponential is needed to fit data TKE tor= 13. 88(5) ps tint= 2. 15(5) ps Aor = 0. 57(1) Aor=1 -Aint OKE [1] tor= 13. 3(1) ps tint= 2. 9(1) ps Aor = 0. 88 Ratio tor: 1. 1 tint: 0. 8 Aor: 0. 7 [1] Loughnane, Brian J. , Alessandra Scodinu, and John T. Fourkas. "Temperature-dependent optical Kerr effect spectroscopy of aromatic liquids. " The Journal of Physical Chemistry B 110. 11 (2006): 5708 -5720.

Conclusions TKE is likely complementary to OKE. There is an intermediate TKE response. Need more modeling!! For all samples studied:

Acknowledgments NSF The Blake Group