title: Creation of a 50,000λ long needle-like field with 0.36λ width.
abstract: It is a great challenge to create a needle-like field with properties of long beam length, narrow lateral width, uniformity, and high optical efficiency. Here we show a method that can realize these properties all at once. The key element is a 90° apex-angle concave conical mirror. By using this condenser along with a radially polarized incident beam of a specific field distribution, we numerically created a super slim, uniform, pure needle-like axially polarized field. This axially polarized field has a length of 50,000λ along the optical axis, and its lateral width still maintains a minimum 0.36λ size.
authors.forename: Minning
authors.initials: M
authors.lastname: Zhu
authors.forename: Qing
authors.initials: Q
authors.lastname: Cao
authors.forename: Hua
authors.initials: H
authors.lastname: Gao