High-speed quantum cascade detector characterized with a mid-infrared femtosecond oscillator

Quantum cascade detectors (QCD) are photovoltaic mid-infrared detectors based on intersubband transitions. Owing to the sub-picosecond carrier transport between subbands and the absence of a bias voltage, QCDs are ideally suited for high-speed and room temperature operation. Here, we demonstrate the design, fabrication, and characterization of 4.3 mu m wavelength QCDs optimized for large electrical bandwidth. The detector signal is extracted via a tapered coplanar waveguide (CPW), which was impedance-matched to 50O. Using femtosecond pulses generated by a mid-infrared optical parametric oscillator (OPO), we show that the impulse response of the fully packaged QCDs has a full-width at half-maximum of only 13.4 ps corresponding to a 3-dB bandwidth of more than 20 GHz. Considerable detection capability beyond the 3-dB bandwidth is reported up to at least 50 GHz, which allows us to measure more than 600 harmonics of the OPO repetition frequency reaching 38 dB signal-to-noise ratio without the need of electronic amplification. Published by The Optical Society under the terms of the Creative Commons Attribution 4.0 License.

Automated summary

Quantum cascade detectors (QCDs) based on intersubband transitions are demonstrated to have a large electrical bandwidth optimized for 4.3 μm wavelength. The impulse response of fully packaged QCDs shows a full-width at half-maximum of only 13.4 ps, corresponding to a 3-dB bandwidth of over 20 GHz, with detection capability reported up to at least 50 GHz without the need for electronic amplification.