Monolithic, Optically Coupled, Multi-Section Mid-IR Quantum Cascade Lasers

• Published in: Photonics 2021-12, Vol.8 (12), p.583
• Main Authors: Pierściński, Kamil, Pierścińska, Dorota, Sobczak, Grzegorz, Kuźmicz, Aleksandr, Chmielewski, Krzysztof, Krajewska, Katarzyna, Gutowski, Piotr
• Format: Article
• Language: English
• Subjects: Absorption spectroscopy; coupled cavities; Design; Design modifications; Emissions; Etching; Fabrication; Infrared lasers; Lasers; Molecular beam epitaxy; Plasma etching; Quantum cascade lasers; quantum cascade lasers (QCLs); Spectrum analysis; Tuning; wavelength tuning
• ISSN: 2304-6732; 2304-6732
• DOI: 10.3390/photonics8120583

Mid-infrared (mid-IR λ ≈ 3–12 μm), single-mode-emission Quantum Cascade Lasers (QCLs) are of significant interest for a wide range of applications, especially as the laser sources are chosen for laser absorption spectroscopy. In this work, we present the design, fabrication and characterization of multi-section, coupled-cavity, mid-IR quantum cascade lasers. The purpose of this work is to propose a design modification for a coupled-cavity device, yielding a single-mode emission with a longer range of continuous tuning during the pulse, in contrast to a 2-section device. This effect was obtained and demonstrated in the work. The proposed design of a 3-section coupled-cavity QCL allows for a single-mode emission with 35 dB side-mode suppression ratio. Additionally, the time-resolved spectra of the wavelength shift during pulse operation, show a continuous tuning of ~3 cm−1 during the 2 μs pulse. The devices were fabricated in a slightly modified, standard laser process using dry etching.