title: Generation of Kerr combs centered at 4.5 μm in crystalline microresonators pumped with quantum-cascade lasers.
abstract: We report on the generation of mid-infrared Kerr frequency combs in high-finesse CaF2 and MgF2 whispering-gallery-mode resonators pumped with continuous-wave room-temperature quantum cascade lasers. The combs were centered at 4.5 μm, the longest wavelength to date. A frequency comb wider than one half of an octave was demonstrated when approximately 20 mW of pump power was coupled to an MgF2 resonator characterized with quality factor exceeding 10(8).
authors.forename: Anatoliy A
authors.initials: AA
authors.lastname: Savchenkov
authors.forename: Vladimir S
authors.initials: VS
authors.lastname: Ilchenko
authors.forename: Fabio
authors.initials: F
authors.lastname: Di Teodoro
authors.forename: Paul M
authors.initials: PM
authors.lastname: Belden
authors.forename: William T
authors.initials: WT
authors.lastname: Lotshaw
authors.forename: Andrey B
authors.initials: AB
authors.lastname: Matsko
authors.forename: Lute
authors.initials: L
authors.lastname: Maleki
mesh_terms: D002124:Calcium Fluoride / Q000737:chemistry; D005459:Fluorides / Q000737:chemistry; D007259:Infrared Rays; D054023:Lasers, Semiconductor; D017616:Magnesium Compounds / Q000737:chemistry; D055616:Microtechnology / Q000295:instrumentation*; D055620:Optical Phenomena; D013696:Temperature
chemical_list: D017616:Magnesium Compounds; C031288:magnesium fluoride; D002124:Calcium Fluoride; D005459:Fluorides