title: Electrically pumped semiconductor laser with monolithic control of circular polarization.
abstract: We demonstrate surface emission of terahertz (THz) frequency radiation from a monolithic quantum cascade laser with built-in control over the degree of circular polarization by "fishbone" gratings composed of orthogonally oriented aperture antennas. Different grating concepts for circularly polarized emission are introduced along with the presentation of simulations and experimental results. Fifth-order gratings achieve a degree of circular polarization of up to 86% within a 12°-wide core region of their emission lobes in the far field. For devices based on an alternative transverse grating design, degrees of circular polarization as high as 98% are demonstrated for selected far-field regions of the outcoupled THz radiation and within a collection half-angle of about 6°. Potential and limitations of integrated antenna gratings for polarization-controlled emission are discussed.
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; and.
authors.forename: Patrick
authors.initials: P
authors.lastname: Rauter
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; and.
authors.forename: Jiao
authors.initials: J
authors.lastname: Lin
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; and.
authors.forename: Patrice
authors.initials: P
authors.lastname: Genevet
authors.affiliation: School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Suraj P
authors.initials: SP
authors.lastname: Khanna
authors.affiliation: School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Mohammad
authors.initials: M
authors.lastname: Lachab
authors.affiliation: School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: A
authors.initials: A
authors.lastname: Giles Davies
authors.affiliation: School of Electronic and Electrical Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
authors.forename: Edmund H
authors.initials: EH
authors.lastname: Linfield
authors.affiliation: School of Engineering and Applied Sciences, Harvard University, Cambridge, MA 02138; and capasso@seas.harvard.edu.
authors.forename: Federico
authors.initials: F
authors.lastname: Capasso
keywords: antenna grating; circular polarization control; quantum cascade laser; surface emission; terahertz