Flat Top Optical Frequency Combs Based on a Single-Core Quantum Cascade Laser at Wavelength of ∼ 8.7 μm

• Published in: Chinese physics letters Vol. 40; no. 1; pp. 14201 - 33
• Main Authors: Ma, Yu, Li, Wei-Jiang, Xu, Yun-Fei, Liu, Jun-Qi, Zhuo, Ning, Yang, Ke, Zhang, Jin-Chuan, Zhai, Shen-Qiang, Liu, Shu-Man, Wang, Li-Jun, Liu, Feng-Qi
• Format: Journal Article
• Language: English
• Published: Chinese Physical Society and IOP Publishing Ltd 01.01.2023; Center of Materials Science and Optoelectronics Engineering,University of Chinese Academy of Sciences,Beijing 100049,China; Key Laboratory of Semiconductor Materials Science,and Beijing Key Laboratory of Low Dimensional Semiconductor Materials and Devices,Institute of Semiconductors,Chinese Academy of Sciences,Beijing 100083,China
• ISSN: 0256-307X; 1741-3540
• DOI: 10.1088/0256-307X/40/1/014201

We present optical frequency combs with a spectral emission of 48 cm −1 and an output power of 420 mW based on a single-core quantum cascade laser at λ ∼ 8.7 μm. A flat top spectrum sustains up to 130 comb modes delivering ∼ 3.2 mW of optical power per mode, making it a valuable tool for dual comb spectroscopy. The homogeneous gain medium, relying on a slightly diagonal bound-to-continuum structure, promises to provide a broad and stable gain for comb operating. Remarkably, the dispersion of this device is measured within 300 fs 2 /mm to ensure stable comb operation over 90% of the total current range. The comb is observed with a narrow beatnote linewidth around 2 kHz and has weak dependence on the applied current for stable comb operation.