Photonics

Research

9 pages, 917 KiB

Open AccessCommunication

Mode-Conversion-Based Chirped Bragg Gratings on Thin-Film Lithium Niobate

by Donghe Tu, Xingrui Huang, Yuxiang Yin, Hang Yu, Zhiguo Yu, Huan Guan and Zhiyong Li

Photonics 2022, 9(11), 828; https://doi.org/10.3390/photonics9110828 - 4 Nov 2022

Cited by 3 | Viewed by 2267

In this work, we propose a mode-conversion-based chirped Bragg grating on thin-film lithium niobate (TFLN). The device is mainly composed of a 4.7-mm long chirped asymmetric Bragg grating and an adiabatic directional coupler (ADC). The mode conversion introduced by the ADC allows the [...] Read more.

In this work, we propose a mode-conversion-based chirped Bragg grating on thin-film lithium niobate (TFLN). The device is mainly composed of a 4.7-mm long chirped asymmetric Bragg grating and an adiabatic directional coupler (ADC). The mode conversion introduced by the ADC allows the chirped Bragg grating operates in reflection without using an off-chip circulator. The proposed device has experimentally achieved a total time delay of 73.4 ps over an operating bandwidth of 15 nm. This mode-conversion-based chirped Bragg grating shows excellent compatibility with other devices on TFLN, making it suitable in monolithically integrated microwave photonics, sensing, and optical communication systems. Full article

(This article belongs to the Special Issue Chip-Scale Photonic Devices for Optical Communication and Information Processing)

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8 pages, 1762 KiB

Open AccessCommunication

Two-Dimensional Elliptical Microresonator Arrays for Wide Flat Bandwidth and Boxlike Filter Response

by Huan Guan, Xingrui Huang, Donghe Tu, Hang Yu, Yuxiang Yin, Zhiguo Yu and Zhiyong Li

Photonics 2022, 9(11), 814; https://doi.org/10.3390/photonics9110814 - 28 Oct 2022

Viewed by 1075

Abstract

Based on two-dimensional elliptical microresonator arrays, we designed and fabricated a compact filter on the silicon-on-insulator platform with potential applications for on-chip optical interconnects. The fabricated optical filter exhibits a wide flat bandwidth of 951 GHz with the shape factor of 0.57 at [...] Read more.

Based on two-dimensional elliptical microresonator arrays, we designed and fabricated a compact filter on the silicon-on-insulator platform with potential applications for on-chip optical interconnects. The fabricated optical filter exhibits a wide flat bandwidth of 951 GHz with the shape factor of 0.57 at the through port for the

3 \times 20

arrays. The out-of-band rejection is as high as 50 dB. The crosstalk is also very low (−46 dB). The spectral shows a boxlike response. Although there are sixty rings used in the array, the insertion loss is still very small (≤1.36 dB). Full article

(This article belongs to the Special Issue Chip-Scale Photonic Devices for Optical Communication and Information Processing)

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6 pages, 3255 KiB

Open AccessCommunication

50 Gb/s Electro-Absorption Modulator Integrated with a Distributed Feedback Laser for Passive Optical Network Systems

by Daibing Zhou, Song Liang, Ruikang Zhang, Qiulu Yang, Xuyuan Zhu, Dan Lu, Lingjuan Zhao and Wei Wang

Photonics 2022, 9(10), 780; https://doi.org/10.3390/photonics9100780 - 20 Oct 2022

Cited by 1 | Viewed by 2274

Abstract

We report an electro-absorption modulator integrated with a distributed feedback Bragg laser fabricated by butt-joint technology. The lasing wavelength of the EML laser was 1311.71 nm, the output power was 10.04 mW when the current of the DFB section was 100 mA, the [...] Read more.

We report an electro-absorption modulator integrated with a distributed feedback Bragg laser fabricated by butt-joint technology. The lasing wavelength of the EML laser was 1311.71 nm, the output power was 10.04 mW when the current of the DFB section was 100 mA, the side-mode suppression ratio was greater than 50 dB, and the small-signal bandwidth was 29.40 GHz when the bias voltage of the modulator was −2 V. A 50 Gb/s data transmission over a single-mode fiber of up to 10 km was realized, which could be used as a light source for 50 G passive optical network systems. Full article

(This article belongs to the Special Issue Chip-Scale Photonic Devices for Optical Communication and Information Processing)

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7 pages, 2084 KiB

Open AccessCommunication

Compact, High Extinction Ratio, and Low-Loss Polarization Beam Splitter on Lithium-Niobate-On-Insulator Using a Silicon Nitride Nanowire Assisted Waveguide and a Grooved Waveguide

by Jinming Tao, Xintong Li, Jinye Li, Shuangxing Dai, Yiru Zhao, Chuangchuang Wei and Jianguo Liu

Photonics 2022, 9(10), 779; https://doi.org/10.3390/photonics9100779 - 19 Oct 2022

Cited by 2 | Viewed by 1835

Abstract

We propose a compact, high extinction ratio, and low-loss polarization beam splitter (PBS) on a lithium-niobate-on-insulator (LNOI) platform, based on an asymmetrical directional coupler and using a silicon nitride nanowire assisted waveguide (WG) and a grooved WG. By properly designing [...] Read more.

We propose a compact, high extinction ratio, and low-loss polarization beam splitter (PBS) on a lithium-niobate-on-insulator (LNOI) platform, based on an asymmetrical directional coupler and using a silicon nitride nanowire assisted waveguide (WG) and a grooved WG. By properly designing

{Si}_{3} N_{4}

nanowires and grooved LN WGs, TE polarization meets the phase matching condition, while significant mismatching exists for TM polarization. Numerical simulations show that the PBS has an ultra-high extinction ratio (ER) of

{TE}_{0}

and

{TM}_{0}

(larger than 40 dB and 50 dB, respectively). The device extinction ratios are larger than 10 dB over 100 nm wavelength ranges. Moreover, the device has an ultra-low insertion loss (IL less than 0.05 dB) at the wavelength of 1550 nm and maintains ILs less than 0.4 dB over 100 nm wavelength ranges. Full article

(This article belongs to the Special Issue Chip-Scale Photonic Devices for Optical Communication and Information Processing)

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8 pages, 11347 KiB

Open AccessCommunication

High Efficiency and High Bandwidth Double-Cladding Waveguide Photodetector Array for 400 Gbit/s Communication

by Fan Xiao, Han Ye, Shuai Wang, Yimiao Chu and Qin Han

Photonics 2022, 9(10), 703; https://doi.org/10.3390/photonics9100703 - 28 Sep 2022

Viewed by 1309

Abstract

A parallel array of 10 side-illuminated waveguide photodetectors (WGPDs) with double-cladding structure was designed and fabricated. In order to achieve high coupling efficiency to the fiber, the thicknesses of InGa_0.24As_0.53P cladding layers and In_0.53Ga_0.47As core [...] Read more.

A parallel array of 10 side-illuminated waveguide photodetectors (WGPDs) with double-cladding structure was designed and fabricated. In order to achieve high coupling efficiency to the fiber, the thicknesses of InGa_0.24As_0.53P cladding layers and In_0.53Ga_0.47As core layer were optimized. The array exhibited a uniform responsivity of 0.54 A/W at 1310 nm without anti-reflection (AR) coating and dark currents lower than 1.3 nA at −5 V. Each photodetector (PD) showed a bandwidth of over 30 GHz, amounting to 400 Gbit/s transmission capacity for the whole chip. In addition, numerical analysis showed that the fiber alignment tolerance to the chip edge along vertical and horizontal directions, when using a lensed fiber, were 1.8 μm and 4.6 μm, respectively. The simple fabrication, easy alignment capability and high performance make the photodetector array a competitive solution for future 400 Gbit/s parallel communication. Full article

(This article belongs to the Special Issue Chip-Scale Photonic Devices for Optical Communication and Information Processing)

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9 pages, 2908 KiB

Open AccessArticle

Flat Optical Frequency Comb Generation Based on Monolithic Integrated LNOI Intensity and Phase Modulator

by Yujia Zhang, Xuanhao Wang, Zhengkai Li, Weiqiang Lyu, Yanjia Lyu, Cheng Zeng, Zhiyao Zhang, Shangjian Zhang, Yali Zhang, Heping Li, Jinsong Xia and Yong Liu

Photonics 2022, 9(7), 495; https://doi.org/10.3390/photonics9070495 - 14 Jul 2022

Cited by 5 | Viewed by 2470

Abstract

A flat optical frequency comb (OFC) is generated by using a monolithic integrated electro-optic intensity and phase modulator fabricated on lithium niobite on insulator (LNOI) platform. The LNOI-based modulation chip consists of a push–pull Mach–Zehnder modulator (MZM) and a U-shaped phase modulator (PM) [...] Read more.

A flat optical frequency comb (OFC) is generated by using a monolithic integrated electro-optic intensity and phase modulator fabricated on lithium niobite on insulator (LNOI) platform. The LNOI-based modulation chip consists of a push–pull Mach–Zehnder modulator (MZM) and a U-shaped phase modulator (PM) connected by a curved optical waveguide. Microwave and optical packaging are implemented for the modulation chip, where the input and output pigtails of the packaged modulation device are polarization-maintaining fibers, with a core diameter of 6.5 μm. The packaged LNOI-based modulation device is featured by a fiber-to-fiber insertion loss as low as 6.97 dB. The half-wave voltages of the MZM and the PM are measured to be 3.6 V and 3.4 V at 5 GHz, respectively. By using the modulation device, an OFC with a tooth spacing of 5 GHz is generated, and the 13 comb teeth in the generated OFC are with a power flatness of 2.4 dB. The measured results of this device indicate that the tooth spacing of the generated OFC can be extended to tens of gigahertz by using a microwave source with a higher output frequency. In addition, the number of the comb teeth can be enhanced beyond 20 by increasing the power of the radio-frequency signal applied to the PM or by further reducing the half-wave voltage of the PM. Full article

(This article belongs to the Special Issue Chip-Scale Photonic Devices for Optical Communication and Information Processing)

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9 pages, 3132 KiB

Open AccessArticle

The Design of a Low-Loss, Fast-Response, Metal Thermo-Optic Phase Shifter Based on Coupled-Mode Theory

by Weiyu Tong, Yanxian Wei, Hailong Zhou, Jianji Dong and Xinliang Zhang

Photonics 2022, 9(7), 447; https://doi.org/10.3390/photonics9070447 - 25 Jun 2022

Cited by 4 | Viewed by 2174

Abstract

A thermo-optic phase shifter is of great importance in silicon photonics. However, it is difficult to simultaneously achieve a good performance in insertion loss and in response speed by using traditional thermal tuning through a metallic heater. In this paper, based on coupled-mode [...] Read more.

A thermo-optic phase shifter is of great importance in silicon photonics. However, it is difficult to simultaneously achieve a good performance in insertion loss and in response speed by using traditional thermal tuning through a metallic heater. In this paper, based on coupled-mode theory, we propose a method to place high-loss materials close to the optical waveguide while maintaining the low loss of the optical device, which ensures the low insertion loss (~0.78 dB) of the phase shifter. Additionally, thanks to the very short distance between the rib waveguide and the chromium (Cr) heater, the phase shifter exhibits a high response speed (1.15 μs in rise time and 2.18 μs in decay time) with a measured bandwidth (BW) of 186 kHz. Moreover, we further optimize the structure of phase shifters, leading to the reduction of π-shift power consumption from 25.1 mW to 13.6 mW. Our proposed phase shifters have great potential in large-scale silicon photonic integrated circuits. Full article

(This article belongs to the Special Issue Chip-Scale Photonic Devices for Optical Communication and Information Processing)

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9 pages, 1294 KiB

Open AccessArticle

Linearity-Enhanced Dual-Parallel Mach–Zehnder Modulators Based on a Thin-Film Lithium Niobate Platform

by Xingrui Huang, Yang Liu, Donghe Tu, Zhiguo Yu, Qingquan Wei and Zhiyong Li

Photonics 2022, 9(3), 197; https://doi.org/10.3390/photonics9030197 - 18 Mar 2022

Cited by 11 | Viewed by 3028

Abstract

In this work, we report a linearity-enhanced dual-parallel Mach–Zehnder modulator (MZM) on a thin-film lithium niobate platform. By setting the optical and electrical splitting ratios at a specific condition, the third-order intermodulation distortions (IMD3) of the child MZMs cancel with each other, whereas [...] Read more.

In this work, we report a linearity-enhanced dual-parallel Mach–Zehnder modulator (MZM) on a thin-film lithium niobate platform. By setting the optical and electrical splitting ratios at a specific condition, the third-order intermodulation distortions (IMD3) of the child MZMs cancel with each other, whereas the first-order harmonics (FH) reach the maximum. Passive devices instead of thermo-optical switches are used to control the optical power and phase of the child MZMs, which greatly improve the device stability and simplify the operation complexity. To the best of our knowledge, the experimental results show a record-high spurious-free dynamic range on a thin-film lithium niobate platform (110.7 dB·Hz

^{2 / 3}

at 1 GHz). The E-O response decayed about 1.9 dB from 10 MHz to 40 GHz, and the extrapolated E-O 3 dB bandwidth is expected to be 70 GHz. A half-wave voltage of 2.8 V was also achieved. The proposed modulator provides a promising solution for high-bandwidth and low-voltage analog optical links. Full article

(This article belongs to the Special Issue Chip-Scale Photonic Devices for Optical Communication and Information Processing)

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