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Optical Design and Fabrication|95 Article(s)
Single-point tunable and non-volatile Y-junction photonic power splitter on SOI with broadband and low loss|On the Cover
Haitang Li, Jin Deng, Junbo Feng, Lehan Zhao, Zihan Shen, Guangqiong Xia, Zhengmao Wu, Jiagui Wu, and Junbo Yang
Y-junction photonic power splitters are essential in photonic integrated circuits. In this paper, a tunable Y-junction splitter is introduced using a standard silicon-on-insulator platform. It features a single-point control mechanism of both the turnability of power splitting ratios and the non-volatility with optical phase change materials (O-PCMs). This nonvolatile Y-junction splitter has a broadband of 350 nm (from 1300 to 1650 nm) with an about 0.7 dB low insertion loss. Using the direct binary search (DBS) inverse design algorithm, a circular point was identified to fill the phase change material Sb2S3 within the coupling area of the Y-junction photonic power splitter. Six example power splitting ratios of 1.86, 1.70, 1.50, 1.34, 1.21, and 1.14 were realized under single-point control using phase changes at 1550 nm with a 0.35 dB low insertion loss. Furthermore, we also implemented a five-stage cascaded array, with the final stage consisting of 16 Y-junction splitters. These results are useful for significantly simplifying the control of photonic circuits. Y-junction photonic power splitters are essential in photonic integrated circuits. In this paper, a tunable Y-junction splitter is introduced using a standard silicon-on-insulator platform. It features a single-point control mechanism of both the turnability of power splitting ratios and the non-volatility with optical phase change materials (O-PCMs). This nonvolatile Y-junction splitter has a broadband of 350 nm (from 1300 to 1650 nm) with an about 0.7 dB low insertion loss. Using the direct binary search (DBS) inverse design algorithm, a circular point was identified to fill the phase change material Sb2S3 within the coupling area of the Y-junction photonic power splitter. Six example power splitting ratios of 1.86, 1.70, 1.50, 1.34, 1.21, and 1.14 were realized under single-point control using phase changes at 1550 nm with a 0.35 dB low insertion loss. Furthermore, we also implemented a five-stage cascaded array, with the final stage consisting of 16 Y-junction splitters. These results are useful for significantly simplifying the control of photonic circuits.
Chinese Optics Letters
- Publication Date: Feb. 28, 2025
- Vol. 23, Issue 2, 022201 (2025)
Low-loss and broadband complementary dual-output electro-optic modulator based on thin-film lithium niobate
Tingan Li, Chenglin Shang, Xuanhao Wang, Weiqiang Lü, Zhiyao Zhang, Cheng Zeng, Yong Liu, and Jinsong Xia
Broadband, low-drive voltage electro-optic modulators are crucial optoelectronic components in the new-generation microwave photonic links and broadband optical interconnect network applications. In this paper, we fabricate a low-loss thin-film lithium niobate complementary dual-output electro-optic modulator chip with a 3 dB electro-optic bandwidth of 59 GHz and a half-wave voltage (Vπ) of 2.5 V. The insert-loss of the packaged modulator is 4.2 dB after coupling with polarization-maintaining fiber. The complementary dual-output modulator also shows a common-mode rejection ratio of 18 dB and a signal enhancement of 6.2 dB when adapted in microwave photonic links, comparable to commercial bulk lithium niobate devices. Broadband, low-drive voltage electro-optic modulators are crucial optoelectronic components in the new-generation microwave photonic links and broadband optical interconnect network applications. In this paper, we fabricate a low-loss thin-film lithium niobate complementary dual-output electro-optic modulator chip with a 3 dB electro-optic bandwidth of 59 GHz and a half-wave voltage (Vπ) of 2.5 V. The insert-loss of the packaged modulator is 4.2 dB after coupling with polarization-maintaining fiber. The complementary dual-output modulator also shows a common-mode rejection ratio of 18 dB and a signal enhancement of 6.2 dB when adapted in microwave photonic links, comparable to commercial bulk lithium niobate devices.
Chinese Optics Letters
- Publication Date: Sep. 11, 2024
- Vol. 22, Issue 9, 092201 (2024)
Fabrication-constrained inverse design and demonstration of high-performance grating couplers
Xin Jin, Jinbin Xu, Yaqian Li, Cuiwei Xue, Rujun Liao, Liucheng Fu, Min Liu, Yunliang Shen, Xueling Quan, and Xiulan Cheng
A high-performance grating coupler (GC) operating at a wavelength of 1550 nm is proposed by utilizing the adjoint-based inverse design algorithm on a 220 nm silicon-on-insulator (SOI) substrate. The grating scheme offers several advantages, including simple structure, large minimum feature size (MFS), manufacturing friendliness, support for large-scale production and multi-project wafer (MPW) runs, etc., while simultaneously maintaining exceptional coupling performance and fabrication tolerance. The design process incorporates various fabrication constraints to satisfy the specifications of different foundry processes. The optimized GC demonstrates excellent coupling performance and 3 dB bandwidth within the MFS range of 60 to 180 nm. The simulated coupling efficiency (CE) of the GC with 130 nm MFS is -1.69 dB, whereas the experimentally measured CE of the fabricated GC using electron beam lithography (EBL) is -2.83 dB. Notably, the experimental CE of the GC with 180 nm MFS fabricated using 248 nm deep ultraviolet (DUV) lithography is -2.77 dB, representing the highest experimental CE ever reported for a single-layer etching C-Band GC supported by MPW runs fabricated on 220 nm SOI without utilizing any back reflector, multi-etch layer, or overlay. The manufacturing outcomes of the same GC structure employing different manufacturing processes are discussed and analyzed, providing valuable insights for the fabrication of silicon photonics devices. A high-performance grating coupler (GC) operating at a wavelength of 1550 nm is proposed by utilizing the adjoint-based inverse design algorithm on a 220 nm silicon-on-insulator (SOI) substrate. The grating scheme offers several advantages, including simple structure, large minimum feature size (MFS), manufacturing friendliness, support for large-scale production and multi-project wafer (MPW) runs, etc., while simultaneously maintaining exceptional coupling performance and fabrication tolerance. The design process incorporates various fabrication constraints to satisfy the specifications of different foundry processes. The optimized GC demonstrates excellent coupling performance and 3 dB bandwidth within the MFS range of 60 to 180 nm. The simulated coupling efficiency (CE) of the GC with 130 nm MFS is -1.69 dB, whereas the experimentally measured CE of the fabricated GC using electron beam lithography (EBL) is -2.83 dB. Notably, the experimental CE of the GC with 180 nm MFS fabricated using 248 nm deep ultraviolet (DUV) lithography is -2.77 dB, representing the highest experimental CE ever reported for a single-layer etching C-Band GC supported by MPW runs fabricated on 220 nm SOI without utilizing any back reflector, multi-etch layer, or overlay. The manufacturing outcomes of the same GC structure employing different manufacturing processes are discussed and analyzed, providing valuable insights for the fabrication of silicon photonics devices.
Chinese Optics Letters
- Publication Date: Nov. 25, 2024
- Vol. 22, Issue 11, 112201 (2024)
Two-photon nanolithography of micrometer scale diffractive neural network with cubical diffraction neurons at the visible wavelength|Editors' Pick
Qi Wang, Haoyi Yu, Zihao Huang, Min Gu, and Qiming Zhang
Free-space diffractive neural networks (DNNs) have been an intense research topic in machine learning for image recognition and encryption due to their high speed, lower power consumption, and high neuron density. Recent advances in DNNs have highlighted the need for smaller device footprints and the shift toward visible wavelengths. However, DNNs fabricated by electron beam lithography, are not suitable for microscopic imaging applications due to their large sizes, and DNNs fabricated by two-photon nanolithography with cylindrical neurons are not optimal for visible wavelengths, as the high-order diffraction could induce low diffraction efficiency. In this paper, we demonstrate that cubical diffraction neurons are more efficient diffraction elements for DNNs compared with cylindrical neurons. Based on the theoretical analysis of the relationship between the detector area sizes and classification accuracy, we reduced the size of DNNs operating at the wavelength of 532 nm for handwritten digit classification to micrometer scale by two-photon nanolithography. The DNNs with cubical neurons demonstrated an experimental classification accuracy (89.3%) for single-layer DNN, and 83.3% for two-layer DNN with device sizes similar to that of biological cells (about 100 µm × 100 µm). Our results paved the pathway to integrate 3D micrometer-scale DNNs with microscopic imaging systems for biological imaging and cell recognition. Free-space diffractive neural networks (DNNs) have been an intense research topic in machine learning for image recognition and encryption due to their high speed, lower power consumption, and high neuron density. Recent advances in DNNs have highlighted the need for smaller device footprints and the shift toward visible wavelengths. However, DNNs fabricated by electron beam lithography, are not suitable for microscopic imaging applications due to their large sizes, and DNNs fabricated by two-photon nanolithography with cylindrical neurons are not optimal for visible wavelengths, as the high-order diffraction could induce low diffraction efficiency. In this paper, we demonstrate that cubical diffraction neurons are more efficient diffraction elements for DNNs compared with cylindrical neurons. Based on the theoretical analysis of the relationship between the detector area sizes and classification accuracy, we reduced the size of DNNs operating at the wavelength of 532 nm for handwritten digit classification to micrometer scale by two-photon nanolithography. The DNNs with cubical neurons demonstrated an experimental classification accuracy (89.3%) for single-layer DNN, and 83.3% for two-layer DNN with device sizes similar to that of biological cells (about 100 µm × 100 µm). Our results paved the pathway to integrate 3D micrometer-scale DNNs with microscopic imaging systems for biological imaging and cell recognition.
Chinese Optics Letters
- Publication Date: Oct. 09, 2024
- Vol. 22, Issue 10, 102201 (2024)
Parallel ray tracing through freeform lenses with NURBS surfaces
Haisong Tang, Zexin Feng, Dewen Cheng, and Yongtian Wang
We implement Monte Carlo-based parallel ray tracing to achieve quick irradiance evaluation for freeform lenses with non-uniform rational B-splines (NURBS) surfaces. We employ the inverse transform sampling method to sample rays uniformly from the Lambertian light source and adopt the analytical form of the B-spline basis function to achieve fast surface interpolation. When performing parallel calculations for the intersections between the rays and the NURBS surfaces, we propose a parameter transformation method to avoid the parameters escaping from the defined range in the iteration process. Simulation results of two complex picture-generating freeform lenses show that our method is fast and effective. We implement Monte Carlo-based parallel ray tracing to achieve quick irradiance evaluation for freeform lenses with non-uniform rational B-splines (NURBS) surfaces. We employ the inverse transform sampling method to sample rays uniformly from the Lambertian light source and adopt the analytical form of the B-spline basis function to achieve fast surface interpolation. When performing parallel calculations for the intersections between the rays and the NURBS surfaces, we propose a parameter transformation method to avoid the parameters escaping from the defined range in the iteration process. Simulation results of two complex picture-generating freeform lenses show that our method is fast and effective.
Chinese Optics Letters
- Publication Date: May. 04, 2023
- Vol. 21, Issue 5, 052201 (2023)
Flexible omnidirectional reflective film for CO2 laser protection
Wenling Chen, Chao Liu, Yuqi Zou, Zhihe Ren, Yuanzhuo Xiang, Fanchao Meng, Yinsheng Xu, Chong Hou, Sheng Liang, Lüyun Yang, and Guangming Tao
In this Letter, we presented a flexible omnidirectional reflective film made of polymer substrates and multiple alternating layers of two chalcogenide glasses for full-angle CO2 laser protection. The structure parameters of the device were simulated for theoretical prediction of best device structure. The reflector was fabricated by alternate thermal evaporation of two chalcogenide glasses with large refractive index contrast. The reflectivity was greater than 78% at 10.6 µm. The flexible reflective film can provide an effective solution for full-angle CO2 laser protection of the moving targets, such as laser operators and mobile optical components, with potential applications for wearable laser protective clothing. In this Letter, we presented a flexible omnidirectional reflective film made of polymer substrates and multiple alternating layers of two chalcogenide glasses for full-angle CO2 laser protection. The structure parameters of the device were simulated for theoretical prediction of best device structure. The reflector was fabricated by alternate thermal evaporation of two chalcogenide glasses with large refractive index contrast. The reflectivity was greater than 78% at 10.6 µm. The flexible reflective film can provide an effective solution for full-angle CO2 laser protection of the moving targets, such as laser operators and mobile optical components, with potential applications for wearable laser protective clothing.
Chinese Optics Letters
- Publication Date: Sep. 13, 2022
- Vol. 21, Issue 2, 022201 (2023)
Multi-direction bending sensing based on spot pattern demodulation of dual-hole fiber
Boyao Li, Yaoyao Liang, Zhongye Xie, Xiaojie Zuo, and Jinghua Sun
A multi-direction bending sensor based on spot pattern demodulation of a dual-hole fiber (DHF) is proposed. By using the interference and scattering in a DHF, the related multidirectional variations can be captured by the optical field. Furthermore, the multi-directional bending characteristics of the fiber are quantitatively described by the pattern of the output light spot, achieving multidirectional bending sensing. In addition, considering the subtle changes in the deformation patterns over time, a convolutional neural network (CNN) model based on deep learning is introduced for accurate recognition and prediction of the bending angle. The experimental results show that the sensor can perceive different bending angles in four directions. These outstanding results indicate that the multi-directional bending sensor based on dual-hole interference pattern decoding has potential applications in multi-directional quantitative sensing and artificial intelligence perception. A multi-direction bending sensor based on spot pattern demodulation of a dual-hole fiber (DHF) is proposed. By using the interference and scattering in a DHF, the related multidirectional variations can be captured by the optical field. Furthermore, the multi-directional bending characteristics of the fiber are quantitatively described by the pattern of the output light spot, achieving multidirectional bending sensing. In addition, considering the subtle changes in the deformation patterns over time, a convolutional neural network (CNN) model based on deep learning is introduced for accurate recognition and prediction of the bending angle. The experimental results show that the sensor can perceive different bending angles in four directions. These outstanding results indicate that the multi-directional bending sensor based on dual-hole interference pattern decoding has potential applications in multi-directional quantitative sensing and artificial intelligence perception.
Chinese Optics Letters
- Publication Date: Dec. 06, 2023
- Vol. 21, Issue 12, 122201 (2023)
Femtosecond laser writing of low-loss three-dimensional waveguide coupler in LiNbO3 crystal
Jinman Lü, Ge Li, Yujie Ma, and Feng Chen
With different interactions between material and femtosecond lasers, two-dimensional (2D) and three-dimensional (3D) waveguide couplers, whose separation distances are fabricated in z-cut lithium niobate crystal by femtosecond laser writing, are reported. Experimentally and numerically, it is shown from results that the guidance is only propagating along TM polarization due to the Type I modification and holds equal splitting ratios, which are the same as power splitters at 632.8 nm. The propagation losses of 2D and 3D waveguide couplers exhibit better transmission properties than those of the previously reported Type I Y-junction waveguide splitters. With different interactions between material and femtosecond lasers, two-dimensional (2D) and three-dimensional (3D) waveguide couplers, whose separation distances are fabricated in z-cut lithium niobate crystal by femtosecond laser writing, are reported. Experimentally and numerically, it is shown from results that the guidance is only propagating along TM polarization due to the Type I modification and holds equal splitting ratios, which are the same as power splitters at 632.8 nm. The propagation losses of 2D and 3D waveguide couplers exhibit better transmission properties than those of the previously reported Type I Y-junction waveguide splitters.
Chinese Optics Letters
- Publication Date: Nov. 01, 2023
- Vol. 21, Issue 11, 112201 (2023)
Plasmon hybridization induced by quasi bound state in the continuum of graphene metasurfaces oriented for high-accuracy polarization-insensitive two-dimensional sensors
Xiuyu Wang, Jihong Xin, Qun Ren, Haocheng Cai, Jiaqi Han, Chengyi Tian, Pengcheng Zhang, Lijie Jiang, Zhihao Lan, Jianwei You, and Wei E. I. Sha
Plasmonics could provide compact and powerful solutions for manipulating light in deep-subwavelength dimensions, which is promising for a great range of nanophotonic technologies such as plasmonic rulers and sensors. However, the effective area of enhanced localized field induced by surface plasmon polaritons is typically restricted to the structural boundaries. In this work, we propose a method to generate high quality-factor extended electromagnetic fields via hybridizing the super-radiant state and the quasi bound state in the continuum of graphene metasurfaces. The coupling interaction involved operates as a three-level system with multiple sharp resonances immune to the polarization, which holds great promise for developing nanodevices with high sensing capacity in two dimensions. Plasmonics could provide compact and powerful solutions for manipulating light in deep-subwavelength dimensions, which is promising for a great range of nanophotonic technologies such as plasmonic rulers and sensors. However, the effective area of enhanced localized field induced by surface plasmon polaritons is typically restricted to the structural boundaries. In this work, we propose a method to generate high quality-factor extended electromagnetic fields via hybridizing the super-radiant state and the quasi bound state in the continuum of graphene metasurfaces. The coupling interaction involved operates as a three-level system with multiple sharp resonances immune to the polarization, which holds great promise for developing nanodevices with high sensing capacity in two dimensions.
Chinese Optics Letters
- Publication Date: Mar. 10, 2022
- Vol. 20, Issue 4, 042201 (2022)
Fabrication of the high-
Shuai Wan, Rui Niu, Jin-Lan Peng, Jin Li, Guang-Can Guo, Chang-Ling Zou, and Chun-Hua Dong
The microresonator-based soliton microcomb has shown a promising future in many applications. In this work, we report the fabrication of high quality (Q) Si3N4 microring resonators for soliton microcomb generation. By developing the fabrication process with crack isolation trenches and annealing, we can deposit thick stoichiometric Si3N4 film of 800 nm without cracks in the central area. The highest intrinsic Q of the Si3N4 microring obtained in our experiments is about 6×106, corresponding to a propagation loss as low as 0.058 dBm/cm. With such a high Q film, we fabricate microrings with the anomalous dispersion and demonstrate the generation of soliton microcombs with 100 mW on-chip pump power, with an optical parametric oscillation threshold of only 13.4 mW. Our Si3N4 integrated chip provides an ideal platform for researches and applications of nonlinear photonics and integrated photonics. The microresonator-based soliton microcomb has shown a promising future in many applications. In this work, we report the fabrication of high quality (Q) Si3N4 microring resonators for soliton microcomb generation. By developing the fabrication process with crack isolation trenches and annealing, we can deposit thick stoichiometric Si3N4 film of 800 nm without cracks in the central area. The highest intrinsic Q of the Si3N4 microring obtained in our experiments is about 6×106, corresponding to a propagation loss as low as 0.058 dBm/cm. With such a high Q film, we fabricate microrings with the anomalous dispersion and demonstrate the generation of soliton microcombs with 100 mW on-chip pump power, with an optical parametric oscillation threshold of only 13.4 mW. Our Si3N4 integrated chip provides an ideal platform for researches and applications of nonlinear photonics and integrated photonics.
Chinese Optics Letters
- Publication Date: Jan. 05, 2022
- Vol. 20, Issue 3, 032201 (2022)
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