Narrowband focusing retroreflector with a thin-film structure. (8th July 2021)

• Record Type: Journal Article
• Authors: Inoue, Junichi; Kusuura, Toshiki; Ueda, Ryohei; Kintaka, Kenji; Ura, Shogo
• Is Part Of: Applied physics express. Volume 14:Number 8(2021)
• Publication Date: 2021-07-08
• Subjects: Subwavelength structures -- Waveguide gratings -- Guided mode resonance -- Wavelength-selective devices -- Retroreflectors; Physics -- Periodicals; Technology -- Periodicals; 621.05
• DOI: 10.35848/1882-0786/ac09bf
• Languages: English
• ISSNs: 1882-0778

Abstract

Abstract: A thin-film narrowband retroreflector is proposed for a diverging free-space wave. The retroreflector consists of a focusing grating coupler in a waveguide resonator on a reflective substrate. The retroreflector is designed and fabricated for an incident wave diverging from a 5.25 μ m diameter spot. The retroreflector gives a reflection towards the divergence point of the incident wave at the resonance wavelength determined by the waveguide resonator, but otherwise a specular reflection. The retroreflection spectrum of a 4 nm bandwidth with the peak of 75% is demonstrated. This configuration will provide a lens-less external-cavity-mirror diode laser of a lasing wavelength fixed to the resonance wavelength.