Photonics Research
Liang Feng; Junqiu Liu; Cheng Wang
Vol. , Issue , 2023
Editor(s): Liang Feng; Junqiu Liu; Cheng Wang
Year: 2023
Status: Published

Guest Editors
Liang Feng, University of Pennsylvania, USA (Lead Editor)

Junqiu Liu, Shenzhen International Quantum Academy, China

Cheng Wang, City University of Hong Kong, China

Contents 5 article(s)
Fully integrated and broadband Si-rich silicon nitride wavelength converter based on Bragg scattering intermodal four-wave mixing
Valerio Vitali, Thalía Domínguez Bucio, Hao Liu, José Manuel Luque González, Francisco Jurado-Romero, Alejandro Ortega-Moñux, Glenn Churchill, James C. Gates, James Hillier, Nikolaos Kalfagiannis, Daniele Melati, Jens H. Schmid, Ilaria Cristiani, Pavel Cheben, J. Gonzalo Wangüemert-Pérez, Íñigo Molina-Fernández, Frederic Gardes, Cosimo Lacava, and Periklis Petropoulos

Intermodal four-wave mixing (FWM) processes have recently attracted significant interest for all-optical signal processing applications thanks to the possibility to control the propagation properties of waves exciting distinct spatial modes of the same waveguide. This allows, in principle, to place signals in different spectral regions and satisfy the phase matching condition over considerably larger bandwidths compared to intramodal processes. However, the demonstrations reported so far have shown a limited bandwidth and suffered from the lack of on-chip components designed for broadband manipulation of different modes. We demonstrate here a silicon-rich silicon nitride wavelength converter based on Bragg scattering intermodal FWM, which integrates mode conversion, multiplexing and de-multiplexing functionalities on-chip. The system enables wavelength conversion between pump waves and a signal located in different telecommunication bands (separated by 60 nm) with a 3 dB bandwidth exceeding 70 nm, which represents, to our knowledge, the widest bandwidth ever achieved in an intermodal FWM-based system.

Photonics Research
Feb. 29, 2024, Vol. 12 Issue 3 A1 (2024)
Power-efficient programmable integrated multiport photonic interferometer in CMOS-compatible silicon nitride
Shuqing Lin, Yanfeng Zhang, Zhaoyang Wu, Shihao Zeng, Qing Gao, Jiaqi Li, Xiaoqun Yu, and Siyuan Yu

Silicon nitride (SiNx) is an appealing waveguide material choice for large-scale, high-performance photonic integrated circuits (PICs) due to its low optical loss. However, SiNx PICs require high electric power to realize optical reconfiguration via the weak thermo-optic effect, which limits their scalability in terms of device density and chip power dissipation. We report a 6-mode programmable interferometer PIC operating at the wavelength of 1550 nm on a CMOS-compatible low-temperature inductance coupled plasma chemical vapor deposition (ICP-CVD) silicon nitride platform. By employing suspended thermo-optic phase shifters, the PIC achieves 2× improvement in compactness and 10× enhancement in power efficiency compared to conventional devices. Reconfigurable 6-dimensional linear transformations are demonstrated including cyclic transformations and arbitrary unitary matrices. This work demonstrates the feasibility of fabricating power-efficient large-scale reconfigurable PICs on the low-temperature ICP-CVD silicon nitride platform.

Photonics Research
Mar. 01, 2024, Vol. 12 Issue 3 A11 (2024)
Heterogeneous tunable III-V-on-silicon-nitride mode-locked laser emitting wide optical spectraSpotlight on Optics
Maximilien Billet, Stijn Cuyvers, Stijn Poelman, Artur Hermans, Sandeep Seema Saseendra, Tasuku Nakamura, Shinya Okamoto, Yasuhisa Inada, Kazuya Hisada, Taku Hirasawa, Joan Ramirez, Delphine Néel, Nicolas Vaissière, Jean Decobert, Philippe Soussan, Xavier Rottenberg, Gunther Roelkens, Jon Ø. Kjellman, and Bart Kuyken

We demonstrate a III-V-on-silicon-nitride mode-locked laser through the heterogeneous integration of a semiconductor optical amplifier on a passive silicon-nitride cavity using the technique of micro-transfer printing. In the initial phase of our study, we focus on optimizing the lasing wavelength to be centered at 1550 nm. This optimization is achieved by conducting experiments with 27 mode-locked lasers, each incorporating optical amplifiers featuring distinct multiple-quantum-well photoluminescence values. Subsequently we present a comprehensive study investigating the behavior of the mode-locking regime when the electrical driving parameters are varied. Specifically, we explore the impact of the gain voltage and saturable absorber current on the locking stability of a tunable mode-locked laser. By manipulating these parameters, we demonstrate the precise control of the optical spectrum across a wide range of wavelengths spanning from 1530 to 1580 nm. Furthermore, we implement an optimization approach based on a Monte Carlo analysis aimed at enhancing the mode overlap within the gain region. This adjustment enables the achievement of a laser emitting a 23-nm-wide spectrum while maintaining a defined 10 dB bandwidth for a pulse repetition rate of 3 GHz.

Photonics Research
Mar. 01, 2024, Vol. 12 Issue 3 A21 (2024)
Large-scale error-tolerant programmable interferometer fabricated by femtosecond laser writing
Ilya Kondratyev, Veronika Ivanova, Suren Fldzhyan, Artem Argenchiev, Nikita Kostyuchenko, Sergey Zhuravitskii, Nikolay Skryabin, Ivan Dyakonov, Mikhail Saygin, Stanislav Straupe, Alexander Korneev, and Sergei Kulik

We introduce a programmable eight-port interferometer with the recently proposed error-tolerant architecture capable of performing a broad class of transformations. The interferometer has been fabricated with femtosecond laser writing, and it is the largest programmable interferometer of this kind to date. We have demonstrated its advantageous error tolerance by showing an operation in a broad wavelength range from 920 to 980 nm, which is particularly relevant for quantum photonics due to efficient photon sources existing in this wavelength range. Our work highlights the importance of developing novel architectures of programmable photonics for information processing.

Photonics Research
Mar. 01, 2024, Vol. 12 Issue 3 A28 (2024)
Reliable intracavity reflection for self-injection locking lasers and microcomb generation
Bitao Shen, Xuguang Zhang, Yimeng Wang, Zihan Tao, Haowen Shu, Huajin Chang, Wencan Li, Yan Zhou, Zhangfeng Ge, Ruixuan Chen, Bowen Bai, Lin Chang, and Xingjun Wang

Self-injection locking has emerged as a crucial technique for coherent optical sources, spanning from narrow linewidth lasers to the generation of localized microcombs. This technique involves key components, namely a laser diode and a high-quality cavity that induces narrow-band reflection back into the laser diode. However, in prior studies, the reflection mainly relied on the random intracavity Rayleigh backscattering, rendering it unpredictable and unsuitable for large-scale production and wide-band operation. In this work, we present a simple approach to achieve reliable intracavity reflection for self-injection locking to address this challenge by introducing a Sagnac loop into the cavity. This method guarantees robust reflection for every resonance within a wide operational band without compromising the quality factor or adding complexity to the fabrication process. As a proof of concept, we showcase the robust generation of narrow linewidth lasers and localized microcombs locked to different resonances within a normal-dispersion microcavity. Furthermore, the existence and generation of localized patterns in a normal-dispersion cavity with broadband forward–backward field coupling is first proved, as far as we know, both in simulation and in experiment. Our research offers a transformative approach to self-injection locking and holds great potential for large-scale production.

Photonics Research
May. 01, 2024, Vol. 12 Issue 5 A41 (2024)
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