Ultra-broadband mode converters based on length-apodized long-period waveguide gratings.

We propose an ultra-broadband mode converter based on the structure of a length-apodized long-period grating, where π-phase shifts are introduced at strategic locations of the grating profile. Using a 3-section length-apodized grating structure, we design and fabricate an LP01-LP11a and an LP01-LP11b mode converter with a sidewall grating and a surface grating formed along a polymer channel waveguide, respectively. The fabricated LP01-LP11a and LP01-LP11b mode converters provide a conversion efficiency higher than 99% over a bandwidth of ~120 nm and ~150 nm, respectively, or a conversion efficiency higher than 90% over a bandwidth of ~180 nm and ~300 nm, respectively. The transmission characteristics of these devices are weakly sensitive to polarization and temperature variations. These mode converters can find applications in ultra-broadband mode-division-multiplexing transmission systems based on few-mode fibers and the design principle can be applied to general grating-based mode-coupling devices for a wide range of applications.

Citation

Wen Wang, Jieyun Wu, Kaixin Chen, Wei Jin, Kin Seng Chiang. Ultra-broadband mode converters based on length-apodized long-period waveguide gratings. Optics express. 2017 Jun 26;25(13):14341-14350

PMID: 28789020

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