Mode and Polarization‐Division Multiplexing Based on Silicon Nitride Loaded Lithium Niobate on Insulator Platform (Laser Photonics Rev. 16(1)/2022)

Han, Xu; Jiang, Yongheng; Frigg, Andreas; Xiao, Huifu; Zhang, Pu; Nguyen, Thach G.; Boes, Andreas; Yang, Jianhong; Ren, Guanghui; Su, Yikai; Mitchell, Arnan; Tian, Yonghui

doi:10.1002/lpor.202270001

Cited by 17 publications

(23 citation statements)

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“…Ta 2 O 5 , Si 3 N 4 , and LiNbO 3 have been widely used in integrated photonics for their CMOS compatibility, low loss, and high nonlinear effect. [ 70–74 ] Compared to silicon, these materials have lower refractive indexes, so the strong interaction between the waveguide modes and the metasurfaces can ensure the efficient mode and polarization conversion process. Please note that our proposed method could be potentially applied to the silicon platform with modified parameters including the size and the period of the C‐shaped nanoantennas.…”

Section: Resultsmentioning

confidence: 99%

On‐Demand Mode Conversion and Wavefront Shaping via On‐Chip Metasurfaces

Deng

Jin

et al. 2022

Advanced Optical Materials

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of external perturbation, controllable mode conversion with polarization change can be implemented. Recently, several methods have been proposed to achieve this goal. For example, waveguides with asymmetric cross-sections, [13][14][15][16][17][18] including L shape and double-stair shape, as well as asymmetric metallic cover layers, [19][20][21] can break the orthogonality of TE 0 and TM 0 mode and hence produce direct conversion between them. Such devices can function as polarization rotators, since the input and output modes always share the same mode order but with different polarization directions. Another method for polarization manipulation is based on mode evolution, where a mode hybridization region is used to gradually convert the input mode into the orthogonal polarization with the same or higher order. [11,22] However, this strategy requires a large length of the mode hybridization region up to hundreds of micrometers because it should satisfy the adiabatic transition condition.Metasurfaces, which are made up of an array of artificial subwavelength structures to locally manipulate the amplitude, phase, and polarization of light, represent one frontier in photonics research. [23][24][25][26][27][28][29][30][31][32] Based on elaborately designed metasurfaces, novel applications such as holographic image display, [33][34][35][36][37][38][39][40][41] imaging with meta-lenses, [42][43][44][45][46][47] orbital angular momentum (OAM) beam generation, [48][49][50][51][52][53] and polarization manipulation [54][55][56][57][58][59] have been demonstrated. However, most of these metasurfaces operate in free space, and the entire systems still consist of bulky optical components including light sources, mirrors, polarizers, etc. To further reduce the overall size and complexity, researchers have recently investigated the hybrid platform by integrating metasurfaces with photonic waveguides that preserve the merits of each system. Applications like mode converters, polarization rotators, second-harmonic generation, on-chip wavefront shaping and OAM lasers have been reported. [60][61][62][63][64][65][66][67] With the assistance of metasurfaces, the wavevector of the guided mode can be modified and the mode coupling coefficient can be optimized, ensuring the efficient conversion from the fundamental mode to higher-order mode. On the other hand, 2D phase shaping of the input planar waveguide mode was realized by deliberately controlling the local phase or refractive index with metasurfaces. [66,68,69] However, to the best of our knowledge, a universal and straightforward method for arbitrarily converting TM modes to TE modes or wavefront shaping for the cross-polarized waves is still lacking.In this paper, we propose a new design strategy for mode converters and polarization rotators utilizing on-chip C-shaped In this work, mode conversion and wavefront shaping by integrating a metallic metasurface on top of a planar waveguide are proposed and demonstrated. The metasurface consists of C-shaped nanoantennas. By controll...

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Section: Resultsmentioning

confidence: 99%

On‐Demand Mode Conversion and Wavefront Shaping via On‐Chip Metasurfaces

Deng

Jin

et al. 2022

Advanced Optical Materials

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“…Thus, the width of the SWG is chosen to be w 5 = 1.8 μm for low loss propagation of TM 0 mode as well as a large effective index difference between TE 0 and TM 0 modes, which is also far away from the mode hybridization width (2.1 μm). [ 23 ] According to the results, the grating pitch is chosen to be Λ 3 = 422 nm in this work, for a central wavelength around 1550 nm. Figure 3c shows the simulated transmission of TE 0 and TM 0 modes as a function of grating period number is simulated at a wavelength of 1550 nm.…”

Section: Principle and Designmentioning

confidence: 99%

“…The device is designed along the crystallographic Z direction on a X‐cut LNOI platform with a 300‐nm‐thick lithium niobate thin film on top of a 4.7‐μm‐thick buried oxide layer, following our previous work. [ 23 ] The birefringence of lithium niobate is considered in the design, which means the crystallographic Z direction has an extraordinary refractive index ( n e ) of ≈2.14, the crystallographic Y/X directions have an ordinary refractive index ( n o ) of ≈2.21, at a wavelength of 1550 nm. The SWG structure is designed on a silicon nitride thin film on the surface of the LNOI platform, whose thickness is chosen to be 300 nm as well, for a strong mode confinement in the hybrid waveguide and a considerable mode confinement factor in the lithium niobate slab.…”

Section: Principle and Designmentioning

confidence: 99%

“…Thus, the silicon nitride‐loaded LNOI waveguides can preserve the excellent material property of lithium niobate whereas overcome the challenges faced by the direct etching waveguide fabrication. [ 21–23 ] For proof‐of‐concept, the SWG waveguides are used to realize spatial mode filters and polarizers which are important components in mode‐division multiplexing (MDM) and polarization‐division multiplexing (PDM) systems, respectively. We have obtained a TE 1 ‐mode‐pass filter, a TE 2 ‐mode‐pass filter and a TM‐pass polarizer with the measured insertion losses of about 1.9, 3.1, and 1.3 dB, respectively, and the measured extinction ratio for all of the devices is larger than 30 dB, at a wavelength of 1550 nm.…”

Section: Introductionmentioning

confidence: 99%

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Integrated Subwavelength Gratings on a Lithium Niobate on Insulator Platform for Mode and Polarization Manipulation

Han

Chen

Jiang

et al. 2022

Laser & Photonics Reviews

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Lithium niobate on insulator (LNOI) has emerged as a promising platform for photonic integrated circuits, with a fast‐growing toolbox of components. This paper proposes, designs, and experimentally demonstrates compact subwavelength grating (SWG) waveguides on an LNOI platform for on‐chip mode and polarization manipulation. To overcome the limitation of waveguide fabrication, the SWGs are designed and formed on a silicon nitride thin film deposited onto the surface of LNOI chip. As proof‐of‐concept devices, the SWG‐based spatial mode filters (including a TE1‐mode‐pass filter and a TE2‐mode‐pass filter) and a TM‐pass polarizer are fabricated successfully on the same chip, with the device lengths of only ≈50 μm. The measured insertion losses for the devices are lower than 3.1 dB, with high extinction ratio larger than 30 dB, at a wavelength of 1550 nm. The proposed and demonstrated SWGs can serve as important building blocks in a series of mode and polarization handling devices for LNOI integrated photonics.

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“…[ 12,35,37 ] The other one is the photonic waveguide formed on LNOI by loading a strip made of another material (such as silicon nitride) thus avoiding the hard etching process. [ 38,39 ] For these two types of LNOI photonic waveguides, there might occur some mode hybridness due to vertical asymmetry as well as material anisotropy. [ 38–40 ] As a result, the design of multimode LN photonic devices has to be very careful (different from silicon photonics), and lots of efforts have been made in recent years.…”

Section: Introductionmentioning

confidence: 99%

High‐Performance Mode‐Multiplexing Device with Anisotropic Lithium‐Niobate‐on‐Insulator Waveguides

Zhao

Liu

Zhu

et al. 2023

Laser & Photonics Reviews

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Thin-film lithium-niobate photonics has attracted intensive attention due to its superior material properties. In particular, multimode lithium-niobate photonics is becoming attractive for the applications of high-capacity optical interconnects and high-efficiency nonlinear optics. However, multimode manipulation in lithium-niobate-on-insulator (LNOI) waveguides is not easy because there might occur some mode hybridness due to the vertical asymmetry as well as the material anisotropy. In this paper, high-performance mode-multiplexing devices with anisotropic LNOI waveguides are proposed, consisting of a multi-channel mode (de)multiplexer and a sharp multimode waveguide bend (MWB). The mode (de)multiplexer is designed with Z-propagation LNOI waveguides to avoid the mode hybridness. Meanwhile, the sharp MWB is designed to connect with a Y-propagation waveguide, enabling access to the highest electro-optic coefficient and second-order nonlinear coefficient. The fabricated mode (de)multiplexer has a low excess loss less than 0.2 dB as well as low crosstalk less than -19 dB in the wavelength range of 1520-1600 nm. These high-performance multimode photonic devices are useful for developing multimode LN photonics.

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Mode and Polarization‐Division Multiplexing Based on Silicon Nitride Loaded Lithium Niobate on Insulator Platform (Laser Photonics Rev. 16(1)/2022)

Cited by 17 publications

References 0 publications

On‐Demand Mode Conversion and Wavefront Shaping via On‐Chip Metasurfaces

On‐Demand Mode Conversion and Wavefront Shaping via On‐Chip Metasurfaces

Integrated Subwavelength Gratings on a Lithium Niobate on Insulator Platform for Mode and Polarization Manipulation

High‐Performance Mode‐Multiplexing Device with Anisotropic Lithium‐Niobate‐on‐Insulator Waveguides

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