Four-channel CWDM device on a thin-film lithium niobate platform using an angled multimode interferometer structure

Gengxin Chen; Ziliang Ruan; Zong Wang; Pucheng Huang; Changjian Guo; Daoxin Dai; Kaixuan Chen; Liu Liu

doi:10.1364/PRJ.438816

Journals >Photonics Research >Volume 10 >Issue 1 >Page 8 > Article

Photonics Research
Vol. 10, Issue 1, 8 (2022)

Four-channel CWDM device on a thin-film lithium niobate platform using an angled multimode interferometer structure

Gengxin Chen¹, Ziliang Ruan¹, Zong Wang², Pucheng Huang², Changjian Guo^2、3, Daoxin Dai¹, Kaixuan Chen^2、3、4, and Liu Liu^1、*

Author Affiliations

¹State Key Laboratory for Modern Optical Instrumentation, College of Optical Science and Engineering, International Research Center for Advanced Photonics, Zhejiang University, Hangzhou 310058, China

²Guangdong Provincial Key Laboratory of Optical Information Materials and Technology, South China Academy of Advanced Optoelectronics, South China Normal University, Higher-Education Mega-Center, Guangzhou 510006, China

³National Center for International Research on Green Optoelectronics, South China Normal University, Guangzhou 510006, China

⁴e-mail: chenkaixuan@m.scnu.edu.cn

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DOI: 10.1364/PRJ.438816 Cite this Article Set citation alerts

Gengxin Chen, Ziliang Ruan, Zong Wang, Pucheng Huang, Changjian Guo, Daoxin Dai, Kaixuan Chen, Liu Liu. Four-channel CWDM device on a thin-film lithium niobate platform using an angled multimode interferometer structure[J]. Photonics Research, 2022, 10(1): 8 Copy Citation Text

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(a) Schematic diagram of the four-channel CWDM on TFLN based on an angled MMI structure. (b) Calculated wavelength dependence of the neff curve for the first five TE modes at WMMI=17.54 μm. (c) Calculated neff curve of the first five TE modes at different WMMI at a wavelength of 1300 nm. (d) Simulated light propagation in the proposed angled MMI structure.

Fig. 1. (a) Schematic diagram of the four-channel CWDM on TFLN based on an angled MMI structure. (b) Calculated wavelength dependence of the neff curve for the first five TE modes at WMMI=17.54 μm. (c) Calculated neff curve of the first five TE modes at different WMMI at a wavelength of 1300 nm. (d) Simulated light propagation in the proposed angled MMI structure.

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Simulated spectral responses of the proposed CWDM device with different tilted angles: (a) θ=0.17 rad, (b) θ=0.15 rad, and (c) θ=0.23 rad. The output waveguide spacing here is Δx=0.88 μm.

Fig. 2. Simulated spectral responses of the proposed CWDM device with different tilted angles: (a) θ=0.17 rad, (b) θ=0.15 rad, and (c) θ=0.23 rad. The output waveguide spacing here is Δx=0.88 μm.

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Fig. 3. Simulated spectral responses of the proposed CWDM device for (a) θ=0.15 rad, Δx=0.1 μm and (b) θ=0.23 rad, Δx=2.79 μm.

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Fig. 4. Simulated fabrication tolerance of the proposed CWDM device with changes (a) in L1 of ΔL1 from −1 to +1 μm, (b) in WMMI of ΔWMMI from −0.04 to +0.04 μm, (c) only in input waveguide width Wa of ΔWa from −2.4 to +2.4 μm, (d) in both input and output waveguide widths Wa of ΔWa from −4 to +4 μm, (e) in t of Δt from −20 to +20 nm, and (f) in h of Δh from −20 to +20 nm for channel #1. Except for the one studied, the rest of the structural parameters are unchanged as shown in Table 1.

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Fig. 5. (a) Microscope image of a fabricated device. Scanning electron microscope images of (b) input coupling grating, (c) input waveguide, (d) output waveguides, and (e) output coupling gratings.

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Fig. 6. (a) Schematic of the measurement setup. (b) Measured spectral response of the fabricated CWDM device. (c) Measured peak wavelength positions (red dots), linear fit (red dotted line), and simulated peak wavelength positions (blue dots) for channel #1 with variations in WMMI.

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$W_{MMI} = 17.54 μm$ , $W_{a} = 5.54 μm$ , $θ = 0.17 rad$ , $Δ x = 0.88 μm$ , $i = 1, 2, 3, 4$
Channel #	1	2	3	4
$λ_{i}$ [nm]	1271	1291	1311	1331
$L_{i}$ [μm]	2054	2017	1980	1943

Table 1. Optimized Structural Parameters for the Four-Channel CWDM Device on TFLN

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$W_{MMI} = 17.54 μm$ , $W_{a} = 5.54 μm$ , $i = 1, 2, 3, 4$
Channel #		1	2	3	4
$θ = 0.15 rad$	$λ_{i}$ [nm]	1265	1287	1309	1331
$Δ x = 0.88 μm$	$L_{i}$ [μm]	2064	2023	1982	1941
$θ = 0.23 rad$	$λ_{i}$ [nm]	1277	1292	1307	1322
$Δ x = 0.88 μm$	$L_{i}$ [μm]	2041	2013	1985	1957

Table 2. Structural Parameters of the Four-Channel CWDM Device on TFLN for Figs. 2(b) and 2(c)

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$W_{MMI} = 17.54 μm$ , $W_{a} = 5.54 μm$ , $i = 1, 2, 3, 4$
Channel #		1	2	3	4
$θ = 0.15 rad$	$λ_{i}$ [nm]	1271	1291	1311	1331
$Δ x = 0.10 μm$	$L_{i}$ [μm]	2053	2015	1977	1939
$θ = 0.23 rad$	$λ_{i}$ [nm]	1271	1291	1311	1331
$Δ x = 2.79 μm$	$L_{i}$ [μm]	2053	2017	1981	1945

Table 3. Structural Parameters of the Four-Channel CWDM Device on TFLN for Figs. 3(a) and 3(b)

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Device	Footprint ( ${mm}^{2}$ )	Channel Amount/Spacing (nm)	Insertion Loss (dB)	${XT}_{center}$ ^a (dB)	${BW}_{3 dB}$
Si [19] PCG	0.25 × 0.16	4/20.2	2.2	23.3	NM^b
Si [20] CMZI	0.3 × 0.1	4/20	$\sim 1$	$\sim 20$	19
Si [22] MMI	0.012 × 1.21	4/21	2	20	12
Si [25] MWG^c	0.6 × 0.04	4/20	$\sim 1$	$\sim 20$	$\sim 15$ ^d
SiN [26] CMZI	1 × 0.6	4/20	$\sim 1.8$	15–24	$\sim 12$ ^d
USRN [27] CVG^e	0.0006 × 8^f	8/20	1	25	7.7
SiN [23] MMI	0.02 × 1.7	4/19	1.5	16–27	11
SiN [21] MWG	0.23 × 1.95	4/20	$< 1.08$	18	10^d
This work	0.02 × 2.1	4/20	$< 0.72$	$\sim 18$	$\sim 12.1$