Advanced High Performance, Thin Film Coatings​

Our group expertise is in optical thin film coatings by reactive ion beam sputtering.We investigate the materials properties and design and characterize multilayer interference coatings for ultra-high power near infrared lasers and ultrastable cavities as in gravitational wave interferometers

We use ion beam sputtering to produce  thin film multilayers of amorphous oxides We specialize in understanding the materials optical and structural properties and in optimizing them.  For high average and peak power near infrared lasers we aim at achieving  high laser damage resistance using different pulse duration scenarios at wavelengths of 800 and 1030 nm.   

Our work on coatings for ultrastable cavities, spart of the LIGO collaboration, focuses on  investigation of ion beam sputtered high index amorphous oxides doped with other materials i.e. Ti:Ta2O5  and nanolaminates of Ta2O5 and other materials as TiO2.  

Current Projects

  • Optical coatings for ultra-high intensity lasers
    • Stress in IBS coatings: Ongoing efforts are investigating how stress in amorphous thin films can be reduced.  Here we are exploring the use of assist beam assistance during deposition.
    • Multilayer dielectric coatings based on amorphous oxides are being developed for chirped pulse amplification lasers operating at 800 nm and 1030 nm.
    • These studies have direct impact in the power scaling of high intensity near infrared lasers, in which interference coatings are one of the weakest components that limits their power scaling.
  • Optical coatings for LIGO(Laser Interferomer Gravitational-Wave Observatory)
    • We use a combination of diagnostics methods to investigate the morphology, bonding and optical properties of high index oxides as Ta2O5 which is the high index component of multilayer mirrors in the test masses of the interferometer. Our work is presently focused on Ta2O5, Ta2O5 doped with other materials, i.e. TiO2 and in nanolaminates or nanolayers made by alternating nanometer thick Ta2O5 with for example TiO2.
      A study of the effect of simultaneous assist bombardment during the deposition of Ta2O5 was also carried out.  It was found the use of Ar and Xe assist did not modify the structural and optical properties of the amorphous Ta2O5.  Neither it modified the mechanical loss.
    • These investigations are contributing to advance the materials that are critical components of LIGO mirrors which is necessary to increase the sensitivity of the interferometer.
  • Surface sculpting with ion beams
    • In this work we use assist ion bombardment at oblique incidence to pattern surfaces with periodic features of controlled size and period.  These patterns have high uniformity over large areas.
    • This work has significance for applications in the engineering of photonics structures such as grating.

Selected Publications

  1. Escola, N. Mingolo, O. E. Martínez, J. J. Rocca, and C. S. Menoni, “Investigation of laser annealing mechanisms in thin film coatings by photothermal microscopy,” Opt. Express 27, 5729-5744 (2019).
  2. Zaldivar Escola, N. Míngolo, O. E. Martínez, J. J. Rocca, and C. S. Menoni, “Characterization of absorptance homogeneity in thin-film coatings for high-power lasers by thermal lensing microscopy,” Appl. Opt. 58, 7233-7240 (2019).
  3. Jankowska, S. Drobczynski, and C.S. Menoni, “Analysis of surface deformation in thin-film coatings by carrier frequency interferometry,” Appl. Opt. 56, C60-C64 (2017).
  4. Schiltz, D. Patel, C. Baumgarten, B.A. Reagan, J.J. Rocca, C.S. Menoni, “Strategies to increase laser damage performance of Ta2O5/SiO2 mirrors by modifications of the top layer design,” Appl. Opt. 56, C136-C139 (2017).


DoD Office of Naval Research, National Science Foundation LIGO Program, DMR Program, and the NSF/Moore Foundation Center for Coatings Research