Optical multimode interference couplers of Ti:LiNbO3 waveguides and electrical tuning of power splitting ratio

OPTICS COMMUNICATIONS

卷:501

Article

Hirai, Anna¹  Matsumoto, Yuichi¹  Sato, Takanori²  Kawai, Tadashi¹  Enokihara, Akira¹  Nakajima, Shinya³  Yamamoto, Naokatsu³ 

[1] Univ Hyogo, Grad Sch Engn, Himeji, Hyogo 6712280, Japan

[2] Hokkaido Univ, Grad Sch Informat Sci & Technol, Sapporo, Hokkaido 0600814, Japan

[3] Natl Inst Informat & Commun Technol, Koganei, Tokyo 1848795, Japan

关键词: Multimode interference (MMI);    Optical coupler;    Titanium-diffused LiNbO3 waveguide;    Tuning;    Power splitting ratio;   

DOI  :  10.1016/j.optcom.2021.127325

来源: Elsevier

【 摘 要 】

We analyzed the optical properties of optical couplers based on multimode interference (MMI) in titanium-diffused LiNbO3 (Ti:LN) waveguides using the beam propagation method (BPM) with refractive index distributions by Ti diffusion. From these results, we designed and fabricated 2 x 2 MMI couplers operating at 1.55 mu m wavelength using Ti:LN waveguides. An optical power splitting ratio of 0.53:0.47 (0.52 dB power deviation from equal split) and an insertion loss of less than 1.5 dB were observed with a coupler consisting of an MMI waveguide 50 mu m wide and 2.12 mm long. Electrical tuning of the power splitting ratio by the electro-optic effect of LiNbO3 was also considered. The electrodes were formed directly on the MMI waveguide section of the coupler and the power splitting ratios were controlled almost in proportion to the voltage applied to the electrode and a deviation of about 1 dB (0.56:0.44) of the power splitting ratio from an equal split could be adjusted to zero by applying a voltage of -6.1 V.

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