title: Experimental investigation of the performance of an annular aperture and a circular aperture on the same very-small-aperture laser facet.
abstract: A very-small-aperture laser (VSAL) with a circular aperture has a trade-off between the spot size and the output power. A nanometric annular aperture is fabricated to overcome this difficulty. The advantages of the annular aperture are demonstrated by measuring and comparing its near-field intensity distribution with that of a circular aperture. These apertures are fabricated on the same VSAL to ensure that they are under the same illumination conditions. The experimental results indicate that an annular aperture produces a smaller spot size and a higher peak intensity than a circular aperture. The confinement effect and the enhancement effect are attributed to the convergence of the power flow that passes through the annular aperture. The observed enhancement effect decreases when the distance from the VSAL facet is increased, but it does not vanish even when the distance is as large as 3.5 microm.
authors.affiliation: State Key Laboratory of Precision Measurement Technology and Instruments, Department of Precision Instruments, Tsinghua University, Beijing 100084, China. gaihf99@mails.tsinghua.edu.cn
authors.forename: Hongfeng
authors.initials: H
authors.lastname: Gai
authors.forename: Jia
authors.initials: J
authors.lastname: Wang
authors.forename: Qian
authors.initials: Q
authors.lastname: Tian
authors.forename: Wei
authors.initials: W
authors.lastname: Xia
authors.forename: Xiangang
authors.initials: X
authors.lastname: Xu