Coherent and Tunable THz Emission Driven by an Integrated III-V Semiconductor Laser

• Published in: IEEE journal of selected topics in quantum electronics Vol. 23; no. 4; pp. 1 - 11
• Main Authors: Blin, Stephane, Paquet, Romain, Myara, Mikhael, Chomet, Baptiste, Le Gratiet, Luc, Sellahi, Mohamed, Beaudoin, Gregoire, Sagnes, Isabelle, Ducournau, Guillaume, Latzel, Philipp, Lampin, Jean-Francois, Garnache, Arnaud
• Format: Journal Article
• Language: English
• Published: IEEE 01.07.2017; Institute of Electrical and Electronics Engineers
• Subjects: Cavity resonators; Electronics; Engineering Sciences; Laser excitation; Laser modes; Laser stability; semiconductor lasers; Submillimeter wave generation; Vertical cavity surface emitting lasers
• ISSN: 1077-260X; 1558-4542
• DOI: 10.1109/JSTQE.2017.2654060

We demonstrate coherent and tunable THz emission by excitation of a unitraveling-carrier photodiode by a dual-frequency III-V semiconductor laser emitting up to 80 mW of optical power around 1 μm. The laser is an optically-pumped vertical-external-cavity surface-emitting laser that operates simultaneously on two transverse Laguerre-Gauss modes. Modes frequency difference is driven by thermal effects, band-filling effects and/or phase masks, allowing THz emission from 50 GHz to few THz. To reach THz emission from a pigtailed photodiode, we detail quantitatively how orthogonal transverse modes can be coupled within a single-mode fiber, leading to more than 20% beat efficiency. Coherent THz emission spectrum is presented with a linewidth of about 150 kHz for 3-ms acquisition time, and an output power limited by the photodiode (typically 1 μW at 300 GHz). Frequency noise is measured for the optical transverse modes along with the THz signal. The latter presents a frequency noise that is about 20-dB lower than the optical ones, thus proving that the dual-frequency concept allows frequency noise reduction by correlating part of the technical noise of the two modes.