Abstract: A thermal radiation detector is disclosed that includes a substrate, a platform suspended above the substrate, a support structure holding the platform, and a temperature sensor disposed on the platform and having an electrical parameter that varies in accordance with the temperature of the temperature sensor. The detector also includes a carbon-nanotube-based optical absorber in thermal contact with the temperature sensor and configured to absorb electromagnetic radiation to generate heat to change the temperature of the temperature sensor. The optical absorber may include a carbon nanotube film, for example, obtained by spray coating. The detector further includes a passivation layer structure disposed over the optical absorber, which may be made of a metal compound, for example, titanium or aluminum oxide. The thermal radiation detector may be a microbolometer detector, a thermocouple/thermopile detector, or a pyroelectric detector.