MODE CONVERSION DEVICE AND DESIGN METHOD

• Main Authors: NAKAJIMA, Kazuhide, YAMASHITA, Yoko, MATSUI, Takashi, MORI, Takayoshi
• Format: Patent
• Language: English
• Published: 02.05.2024
• Subjects: OPTICAL ELEMENTS, SYSTEMS, OR APPARATUS; OPTICS; PHYSICS

An objective of the present invention is to provide a mode conversion device capable of designing any coupling efficiency and full width at half maximum, and a design method therefor.According to the present invention, a mode conversion device includes a long period grating at a core of an optical fiber through which light is able to propagate in at least two propagation modes. The long period grating satisfies a relationship of Expression C1, where a full width at half maximum FWHM is a wavelength band in which the coupling efficiency is a half of coupling efficiency of mode conversion at a center wavelength, C is coupling efficiency, Lc is a complete coupling length, Lg is a grating length, Λ is a grating pitch, and Δβ is a propagation constant difference between the two propagation modes at the center wavelength of a mode conversion target.[Math.C⁢1]Λ=2⁢πΔβC=sin2(π2⁢LgLc)FWHM·Lc=b⁢❘"\[LeftBracketingBar]"d⁢Δ⁢βd⁢λ❘"\[RightBracketingBar]"-1b=-1169.3⁢C+1705.6(C⁢1)