title: The output power and beam divergence behaviors of tapered terahertz quantum cascade lasers.
abstract: We report on Terahertz quantum cascade lasers with tapered waveguide structure operating at ≈ 103 μm. The tapered waveguide effect on the output power and the laser beam divergence are experimentally studied with the tapered angle ranging from 0° to 8°. It is found that the peak output power of the devices with same length reaches the maximum at about 5° ≈ 6° tapered angle. Meanwhile, the horizontal divergence angle of the laser beam can be greatly reduced. The existence of such optimal tapered angle is explained by the finite-element simulation with the consideration of the self-focusing effect for the devices with larger tapered angle.
authors.affiliation: Key Laboratory of Semiconductor Materials Science, Institute of Semiconductors, Chinese Academy of Sciences, 100083, Beijing, China.
authors.forename: YanFang
authors.initials: Y
authors.lastname: Li
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Ning
authors.initials: N
authors.lastname: Yang
authors.forename: Junqi
authors.initials: J
authors.lastname: Liu
authors.forename: Tao
authors.initials: T
authors.lastname: Wang
authors.forename: Fengqi
authors.initials: F
authors.lastname: Liu
authors.forename: Zhanguo
authors.initials: Z
authors.lastname: Wang
authors.forename: Weidong
authors.initials: W
authors.lastname: Chu
authors.forename: Suqing
authors.initials: S
authors.lastname: Duan