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

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.

Application of High-Speed Quantum Cascade Detectors for Mid-Infrared, Broadband, High-Resolution Spectroscopy

“…The optimization of a QC detector for radio-frequency operation was reported in Ref. [ 12 ], where a well-designed coplanar waveguide was used to match the 50 Ω impedance, and no noticeable artifacts appeared in the frequency response up to 50 GHz. However, for broadband heterodyne spectroscopy, the variation of the beat signal intensity up to 25 GHz can be regarded as within the 3-dB cutoff.…”

“…Regarding high-speed operation, an electron transit time of less than 1 ps was substantiated in a near-infrared QC detector by a time-resolved pump–probe measurement [ 10 ]. More recently, frequency responses of several tens of gigahertz and picosecond response times have been demonstrated in the mid-infrared (MIR) QC detectors [ 11 , 12 ]. The intrinsic short response times are determined by high-speed electron transport via sub-picosecond intersubband scattering processes.…”

High-capacity free-space optical link in the midinfrared thermal atmospheric windows using unipolar quantum devices

“…40 Overall, this work shows the relevance of intersubband technology as a key building block of the midinfrared transmission (optical source, external modulator, and detector) and holds much promise as the size-reduction of the modulator is expected to drastically increase the maximum bandwidth, which is a trend already observed in intersubband detectors. 41 2 Optical Setup Our free-space communication setup is represented in Fig. 1.…”

Mid-infrared free-space cryptosystem

“…The quantum cascade laser (QCL) technology has known tremendous improvements in the past two decades, boosted by the need for mid-infrared frequency combs for precision spectroscopy [1] and highpower low-divergence beams [2] for military applications. There is nowadays a growing interest for high-speed devices relying on quantum well and quantum cascade structures either on the emission side [3] or on the reception side [4,5], even if QCLs for free-space communication has long been envisioned [6]. The main advantage of mid-infrared wavelength is that it is less affected by atmospheric conditions than near-infrared wavelength, thus the superiority of mid-infrared light for long-range freespace transmission [7].…”