Open AccessGraphene‐Coupled Terahertz Semiconductor Lasers for Enhanced Passive Frequency Comb Operation
Author(s) -
Li Hua,
Yan Ming,
Wan Wenjian,
Zhou Tao,
Zhou Kang,
Li Ziping,
Cao Juncheng,
Yu Qiang,
Zhang Kai,
Li Min,
Nan Junyi,
He Boqu,
Zeng Heping
Publication year - 2019
Publication title -
advanced science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.388
H-Index - 100
ISSN - 2198-3844
DOI - 10.1002/advs.201900460
Subject(s) - terahertz radiation , graphene , frequency comb , optoelectronics , materials science , saturable absorption , laser , photomixing , optics , mode locking , terahertz spectroscopy and technology , far infrared laser , fiber laser , physics , nanotechnology , terahertz metamaterials , wavelength
Optical frequency combs, consisting of well‐controlled equidistant frequency lines, have been widely used in precision spectroscopy and metrology. Terahertz combs have been realized in quantum cascade lasers (QCLs) by employing either an active mode‐locking or phase seeding technique, or a dispersion compensator mirror. However, it remains a challenge to achieve the passive comb formation in terahertz semiconductor lasers due to the insufficient nonlinearities of conventional saturable absorbers. Here, a passive terahertz frequency comb is demonstrated by coupling a multilayer graphene sample into a QCL compound cavity. The terahertz modes are self‐stabilized with intermode beat note linewidths down to a record of 700 Hz and the comb operation of graphene‐coupled QCLs is validated by on‐chip dual‐comb measurements. Furthermore, the optical pulse emitted from the graphene‐coupled QCL is directly measured employing a terahertz pump–probe technique. The enhanced passive frequency comb operation is attributed to the saturable absorption behavior of the graphene‐integrated saturable absorber mirror, as well as the dispersion compensation introduced by the graphene sample. The results provide a conceptually different graphene‐based approach for passive comb formation in terahertz QCLs, opening up intriguing opportunities for fast and high‐precision terahertz spectroscopy and nonlinear photonics.