Soft X-Ray Second Harmonic Generation as an Interfacial Probe

R.K. Lam, S.L. Raj, T.A. Pascal, C.D. Pemmaraju, L. Foglia, A. Simoncig, N. Fabris, P. Miotti, C.J. Hull, A.M. Rizzuto, J.W. Smith, R. Mincigrucci, C. Masciovecchio, A. Gessini, E. Allaria, G. De Ninno, B. Diviacco, E. Roussel, S. Spampinati, G. PencoS. Di Mitri, M. Trovò, M. Danailov, S.T. Christensen, D. Sokaras, T.-C. Weng, M. Coreno, L. Poletto, W.S. Drisdell, D. Prendergast, L. Giannessi, E. Principi, D. Nordlund, R.J. Saykally, C.P. Schwartz

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Nonlinear optical processes at soft x-ray wavelengths have remained largely unexplored due to the lack of available light sources with the requisite intensity and coherence. Here we report the observation of soft x-ray second harmonic generation near the carbon K edge (∼284 eV) in graphite thin films generated by high intensity, coherent soft x-ray pulses at the FERMI free electron laser. Our experimental results and accompanying first-principles theoretical analysis highlight the effect of resonant enhancement above the carbon K edge and show the technique to be interfacially sensitive in a centrosymmetric sample with second harmonic intensity arising primarily from the first atomic layer at the open surface. This technique and the associated theoretical framework demonstrate the ability to selectively probe interfaces, including those that are buried, with elemental specificity, providing a new tool for a range of scientific problems.
Original languageEnglish
Article number023901
Pages (from-to)-
JournalPhysical Review Letters
Issue number2
Publication statusPublished - 8 Jan 2018
Externally publishedYes


All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

Lam, R. K., Raj, S. L., Pascal, T. A., Pemmaraju, C. D., Foglia, L., Simoncig, A., Fabris, N., Miotti, P., Hull, C. J., Rizzuto, A. M., Smith, J. W., Mincigrucci, R., Masciovecchio, C., Gessini, A., Allaria, E., De Ninno, G., Diviacco, B., Roussel, E., Spampinati, S., ... Schwartz, C. P. (2018). Soft X-Ray Second Harmonic Generation as an Interfacial Probe. Physical Review Letters, 120(2), -. [023901].