Broadband spin‐controlled focusing via logarithmic‐spiral nanoslits of varying width. Issue 6 (19th September 2015)

• Record Type: Journal Article
• Authors: Mehmood, M. Q.; Liu, Hong; Huang, Kun; Mei, Shengtao; Danner, Aaron; Luk'yanchuk, Boris; Zhang, Shuang; Teng, Jinghua; Maier, Stefan A.; Qiu, Cheng‐Wei
• Is Part Of: Laser & photonics reviews. Volume 9:Issue 6(2015:Nov.)
• Page Start: 674
• Page End: 681
• Publication Date: 2015-09-19
• Subjects: logarithmic‐spiral nanoslit -- confined spot -- diffraction -- broadband spin‐controlled focusing; Lasers -- Periodicals; Photonics -- Periodicals; Lasers -- Périodiques; Photonique -- Périodiques; 621.36
• DOI: 10.1002/lpor.201500116
• Languages: English
• ISSNs: 1863-8880

Abstract

Abstract : A logarithmic spiral (LS) nanoslit with switchable focusing functionalities has been experimentally demonstrated as a promising candidate to identify the handedness of incident circular polarization. Strongly depending on spin of incident photons, this LS‐nanoslit converges the incoming light with opposite handedness (with respect to the handedness of the LS‐slit) into a confined subwavelength spot, while the light with identical chirality is structured into a donut‐shape profile at the focal plane. Abstract: This work presents analytical, numerical and experimental demonstrations of light diffracted through a logarithmic spiral (LS) nanoslit, which forms a type of switchable and focus‐tunable structure. Owing to a strong dependence on the incident photon spin, the proposed LS‐nanoslit converges incoming light of opposite handedness (to that of the LS‐nanoslit) into a confined subwavelength spot, while it shapes light with similar chirality into a donut‐like intensity profile. Benefitting from the varying width of the LS‐nanoslit, different incident wavelengths interfere constructively at different positions, i.e., the focal length shifts from 7.5 μm (at λ = 632.8 nm) to 10 μm (at λ = 488 nm), which opens up new opportunities for tuning and spatially separating broadband light at the micrometer scale.