Twelve‐channel LAN wavelength‐division multiplexer on lithium niobate
Jianghao He, Ming Zhang, Dajian Liu, Yaoxin Bao, Chenlei Li, Bingcheng Pan, Yishu Huang, Zejie Yu, Liu Liu, Yaocheng Shi, Daoxin Dai
Abstract
Abstract A twelve‐channel local‐area‐network (LAN) wavelength‐division multiplexing (LWDM) filter is proposed and demonstrated with a uniform channel spacing of 4.5 nm (800 GHz) in the O‐band of 1270–1330 nm by using x‐cut lithium‐niobate‐on‐insulator (LNOI) photonic waveguides for the first time. The present LWDM filter consists of twelve single‐channel bandpass filters based on multimode waveguide gratings (MWGs) assisted with a TE 0 /TE 1 mode (de)multiplexer. In particular, two stages of MWGs in cascade are introduced for each single‐channel bandpass filter, in order to achieve high sidelobe suppression ratios, thus reducing interchannel crosstalk. For the fabricated twelve‐channel LWDM filter, all the channels have very excellent box‐like spectral responses with low excess losses of ∼0.6 dB, broad 1‐dB bandwidths of ∼2.9–3.4 nm (which is close to 75 % of the channel spacing), and ultra‐low interchannel crosstalk of <−40 dB in experiments. In addition, the present device is highly tolerant to the random variations of the etching depth (±20 nm) and the grating waveguide width (±20 nm) of the LNOI photonic waveguides, showing great potential for high‐capacity WDM systems.