Far infrared thermal detectors for laser radiometry using a carbon nanotube array

Area of Science:

• Materials Science
• Nanotechnology
• Optics

Background:

• Vertically aligned carbon nanotube arrays (VANTAs) are explored for their unique optical properties.
• Carbon nanotubes offer potential for advanced sensor applications due to their thermal and electrical characteristics.

Purpose of the Study:

• To characterize the reflectance of VANTAs with varying lengths on infrared detectors.
• To evaluate the performance of VANTAs integrated with thermopile and pyroelectric detectors.
• To assess the thermal properties and response times of the VANTAs.

Main Methods:

• Fabrication and integration of VANTAs (40 μm, 150 μm, 1.5 mm) onto detector surfaces.
• Measurement of reflectance at a laser wavelength of 394 μm (760 GHz).
• Analysis of thermopile responsivity under electrical and optical heating.
• Characterization of frequency and temporal response to determine thermal decay period.

Main Results:

• Reflectance decreased with increasing VANTAs length, from 0.38 (40 μm) to 0.23 (150 μm) to 0.01 (1.5 mm).
• Thermopile responsivity was consistent for both electrical (98.4 mA/W) and optical (98.0 mA/W) heating.
• A thermal decay period of 500 ms was observed, aligning with literature values for VANTAs.

Conclusions:

• The 1.5 mm VANTAs exhibit unprecedentedly low reflectance (0.01) at 760 GHz.
• VANTAs are readily transferable to detector surfaces, demonstrating practical applicability.
• The findings suggest VANTAs are highly promising for enhancing infrared detector performance.