High-performance carbon nanotube coatings for high-power laser radiometry

Abstract

Radiometry for the next generation of high-efficiency, high-power industrial lasers requires thermal management at optical power levels exceeding 10 kW. Laser damage and thermal transport present fundamental challenges for laser radiometry in support of common manufacturing processes, such as welding, cutting, ablation, or vaporization. To address this growing need for radiometry at extremely high power densities, we demonstrate multiwalled carbon nanotube (MWCNT) coatings with damage thresholds exceeding 15 000 W/cm2 and absorption efficiencies over 90% at 1.06 μm. This result demonstrates specific design advantages not possible with other contemporary high-power laser coatings. Furthermore, the results demonstrate a performance difference between MWCNTs and single-walled carbon nanotube coatings, which is attributed to the lower net thermal resistance of the MWCNT coatings. We explore the behavior of carbon nanotubes at two laser wavelengths (1.06 and 10.6 μm) and also evaluate the optical-absorption efficiency and bulk properties of the coatings.

Q-Switched Ultrafast TDFL Using MWCNTs-SA at 2 µm Region

“…This to ensure the thermal and laser damage threshold is higher than SWCNTs. [24], [25] As far as the authors known, there are only few works reported regarding the usage of MWCNTs as saturable absorber in fibre laser application. For instance, Zhang et al [23] employs MWCNTs as saturable absorber for mode locking of neodymium-doped yttrium vanadate (Nd:YVO4) laser.…”

Raman and electron microscopy analysis of carbon nanotubes exposed to high power laser irradiance

“…Further details of the experimental setup are described elsewhere. 8,12,13 Figures 1͑A͒ and 1͑B͒ show images of the exposed grids of SWCNTs and MWCNTs, respectively.…”

“…The beam was focused on an area of ϳ0.25 mm 2 , and the scattered light was analyzed by the use of a 270 mm grating spectrometer. 8,12 For the electron microscopy analysis, the copper substrate was directly attached to the electron microscope sample holder by using carbon tape. Information from the Raman spectra was tabulated to assist in correlation with the structural changes observed by the use of electron microscopy.…”

“…The application of multiwalled carbon nanotubes ͑MWCNTs͒ and singlewalled carbon nanotubes ͑SWCNTs͒ as thermal detector coatings has also been explored. [6][7][8] In our earlier work, we demonstrated a high damage threshold up to 15 kW/ cm 2 upon exposure to 1.06 m irradiance for MWCNT coatings. Raman spectra data have suggested the onset of structural changes in the nanotube coating upon exposure to high power irradiance.…”

“…The sprayed nanotubes were then selectively exposed to incremental laser irradiance up to the level where visual damage to the coating was observed in the form of continuous sparking. 8 Selective exposure of the sample to different irradiance levels was then correlated with the structural changes occurring in the coating through electron microscopy and Raman spectroscopy. In addition to the sprayed CNT samples, a commercially obtained vertically aligned MWCNT sample was also tested and analyzed.…”