Abstract
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 µm wavelength QCDs optimized for large electrical bandwidth. The detector signal is extracted via a tapered coplanar waveguide (CPW), which was impedance-matched to 50 Ω. 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.
Highlights
There is a growing interest in sensitive and high-speed photodetectors operating in the mid-infrared (MIR) range
Using femtosecond pulses generated by a mid-infrared optical parametric oscillator (OPO), we show that the impulse response of the fully packaged Quantum cascade detectors (QCD) has a full-width at half-maximum of only 13.4 ps corresponding to a 3-dB bandwidth of more than 20 GHz
To Quantum well infrared photodetectors (QWIPs), carrier transport in QCDs occurs on the picosecond timescale, which enables high-speed heterodyne detection at room temperature [28,29]
Summary
There is a growing interest in sensitive and high-speed photodetectors operating in the mid-infrared (MIR) range. Recent work has shown that this issue can be mitigated by embedding the QWIP into a patch array antenna [23,24] This technique effectively reduces the electrical area and the dark current of the detector and allows room temperature operation. To QWIPs, carrier transport in QCDs occurs on the picosecond timescale, which enables high-speed heterodyne detection at room temperature [28,29]. It should be noted that interband cascade infrared photodetectors (ICIPs) based on type-II broken band gap structures are emerging as promising candidate for high-speed and spectrally broadband detectors [30,31,32,33] and 7 GHz bandwidth has been reported recently [34]. We present the first temporal characterization of QCDs with a femtosecond MIR oscillator, revealing a fast impulse response of only 13.4 ps
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