Foam-based optical absorber for high-power laser radiometry

Abstract

We report damage threshold measurements of novel absorbers comprised of either liquid-cooled silicon carbide or vitreous carbon foams. The measurements demonstrate damage thresholds up to 1.6 ϫ 10 4 W͞cm 2 at an incident circular spot size of 2 mm with an absorbance of 96% at 1.064 m. We present a summary of the damage threshold as a function of the water flow velocity and the absorbance measurements. We also present a qualitative description of a damage mechanism based on a two-phase heat transfer between the foam and the flowing water.

Evaluating the thermal damage resistance of graphene/carbon nanotube hybrid composite coatings

“…However, Multi-walled carbon nanotube (MWCNT)-based coatings suffer from severe damage or burn at power densities of approx. 1 kW.cm −2 at 10.6  μ m exposure1516.…”

“…But the primary limitations of these coatings are poor laser-damage threshold and low thermal conductivity8. Carbon nanotubes (CNTs) have proven to be a good alternative because of their properties such as high thermal conductivity, high mechanical strength and flat spectral response over a wide wavelength range89101112131415161718192021222324. However, Multi-walled carbon nanotube (MWCNT)-based coatings suffer from severe damage or burn at power densities of approx.…”

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

“…During irradiance the sample was mounted on a holder with port connections for cooling water. 13 It is to be noted here that the coating thickness was not uniform over the sample substrate area ͑62 ϫ 24 mm 2 ͒. The experimental setup employed a 1.25 kW Nd:YAG laser operating at 1.06 m. The incident radiation was allowed to pass through a beamsplitter.…”

“…Calibrated commercial thermistors were mounted on the inlet and outlet water channels to measure the change in water temperature upon transit through the sample. 13 The absorbed power was calculated from the cooling water flow rate and the change in the water temperature. The calibration factor used to determine the incident power was evaluated by replacing the sample holder with a water-cooled power meter.…”

“…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.…”