Low Group Delay Dispersion Optical Coating for Broad Bandwidth High Reflection at 45° Incidence, P Polarization of Femtosecond Pulses with 900 nm Center Wavelength

Journal Article · Tue Mar 01 00:00:00 EST 2016 · Coatings

DOI:https://doi.org/10.3390/coatings6010011· OSTI ID:1249069

Bellum, John C. ^[1]; Field, Ella S. ^[1]; Winstone, Trevor B. ^[2]; Kletecka, Damon E. ^[1]

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1. Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
2. Science and Technology Facilities Council (STFC), Oxford (United Kingdom). Rutherford Appleton Lab. (RAL)

We describe an optical coating design suitable for broad bandwidth high reflection (BBHR) at 45° angle of incidence (AOI), P polarization (Ppol) of femtosecond (fs) laser pulses whose wavelengths range from 800 to 1000 nm. The design process is guided by quarter-wave HR coating properties. Our design must afford low group delay dispersion (GDD) for reflected light over the broad, 200 nm bandwidth in order to minimize temporal broadening of the fs pulses due to dispersive alteration of relative phases between their frequency components. The design should also be favorable to high laser-induced damage threshold (LIDT). We base the coating on TiO₂/SiO₂ layer pairs produced by means of e-beam evaporation with ion-assisted deposition, and use OptiLayer Thin Film Software to explore designs starting with TiO₂/SiO₂ layers having thicknesses in a reverse chirped arrangement. This approach led to a design with R > 99% from 800 to 1000 nm and GDD < 20 fs² from 843 to 949 nm (45° AOI, Ppol). The design’s GDD behaves in a smooth way, suitable for GDD compensation techniques, and its electric field intensities show promise for high LIDTs. Reflectivity and GDD measurements for the initial test coating indicate good performance of the BBHR design. Subsequent coating runs with improved process calibration produced two coatings whose HR bands satisfactorily meet the design goals. Lastly, for the sake of completeness, we summarize our previously reported transmission spectra and LIDT test results with 800 ps, 8 ps and 675 fs pulses for these two coatings, and present a table of the LIDT results we have for all of our TiO₂/SiO₂ BBHR coatings, showing the trends with test laser pulse duration from the ns to sub-ps regimes.

• Research Organization: Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)
• Sponsoring Organization: USDOE National Nuclear Security Administration (NNSA)
• Grant/Contract Number: AC04-94AL85000
• OSTI ID: 1249069
• Report Number(s): SAND-2016-3071J; COATED; 637670
• Journal Information: Coatings, Vol. 6, Issue 1; ISSN 2079-6412
• Publisher: MDPI
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
optical coatings
broad bandwidth high reflection
low group delay dispersion
high laser-induced damage thresholds