The primary challenge for long-wavelength infrared (λ = 8–13 µm) detection has long been the mitigation of dark current while achieving a high conversion efficiency of optical to electrical signals. Often overlooked is the bandwidth of detector response, despite several existing and expected future long-wave infrared high bandwidth applications. Here, we demonstrate ultra-fast response times in long-wave infrared detectors leveraging ultra-thin absorbers. The time response of the detectors is characterized using mid-infrared femtosecond pulses generated by an optical parametric amplifier, as a function of the device temperature and operating bias, as well as excitation wavelength. An equivalent circuit model for the detectors is presented and compared to our experimental results with excellent agreement. We demonstrate detector impulse response times of 3.5 GHz). Spectral response measurements confirm that the detectors have a resonant cavity mode enhanced response in the long-wave infrared, peaking at 10.2 µm. The presented detectors offer a potential solution for a range of high-frequency applications in the long-wave infrared.
