title: Design of high-Q photonic crystal microcavities with a graded square lattice for application to quantum cascade lasers.
abstract: A high-Q photonic crystal (PC) microcavity for TM-like modes, which can be applied to quantum cascade lasers (QCLs), was successfully designed in an air-hole based PC slab with semiconductor cladding layers. In spite of no photonic badgaps for TM-like modes in air-hole based PC slabs, cavity Q reached up to 2,200 by utilizing a graded square lattice PC structure. This is approximately 18 times higher than those previously reported for PC defect-mode microcavities for QCLs. This large improvement is attributed to a suppression of the coupling between the cavity mode and the leaky modes thanks to the dielectric perturbation in the graded structure. We also predicted a dramatic reduction of the threshold current in the designed cavity down to one-fifteenth of that of a conventional QCL, due to a decreased optical volume.
authors.affiliation: Institute of Nano Quantum Information Electronics, The University of Tokyo 4-6-1, Komaba, Meguro-ku, Tokyo 153-8505, Japan. wakayuki@iis.u-tokyo.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Wakayama
authors.forename: A
authors.initials: A
authors.lastname: Tandaechanurat
authors.forename: S
authors.initials: S
authors.lastname: Iwamoto
authors.forename: Y
authors.initials: Y
authors.lastname: Arakawa