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Silicon photonics at the 2 μm waveband, specifically the 1.9 μm wavelength region is strategically imperative. This is due to its infrastructural compatibility (i.e., thulium-doped fiber amplifier, hollow-core photonic bandgap fiber) in enabling communications, as well as its potential to enable a wide range of applications. While the conventional Silicon-on-Insulator platform permits passive/active functionalities, it requires stringent processing due to high-index contrast. On the other hand, SiN can serve to reduce waveguiding losses via its moderate-index contrast. In this work, by demonstrating SiN passives and Si-SiN interlayer coupler with favorable performance, we extend the Si-SiN platform to the 1.9 μm wavelength region. We report waveguide propagation loss of 2.32 dB/cm. Following, trends in radiation loss with regards to bending radius is analyzed. A high performance 3-dB power splitter with insertion loss and bandwidth of 0.05 dB and 55 nm (1935-1990 nm) respectively is introduced. Lastly, Si-SiN transition loss as low as 0.04 dB is demonstrated.

The “ $2~\mu \text{m}$ waveband”, specifically the $1.9~\mu \text{m}$ wavelength region, is playing an increasingly imperative role in photonics. Development into compact tunable light sources operating at the wavelength region can unlock numerous technological applications. Instances, while not exhaustive, include alleviating the capacity load in fiber communications, H2O spectroscopy, optical logic, signal processing as well as enabling the optical Kerr effect on silicon. Silicon photonics is a disruptive technology. Through mature silicon processing, recent developments suggest that silicon will emerge as the workhorse of integrated optics. While the realization of a monolithic light source has proved to be challenging, the hybrid/heterogenous Si platforms, consisting of silicon and III-V materials, has stepped to the fore. In this work, we present the study of Vernier-based hybrid silicon photonic wavelength-tunable lasers with an operating range of 1881–1947 nm (66 nm), subject to different coupling gaps (Gapmrr) between the silicon microring resonators (MRRs) and bus waveguide. Wavelength tuning functionality is enabled via the thermo-optic effect of MRRs. Gapmrr, being the smallest feature in the assemble, is highly influential to the characteristics of the SHREC. As such, trends in hybrid laser performance with respect to Gapmrr are measured and analyzed. Slope efficiency, laser output power and side-mode suppression ratio of 0.232 W/A, 28 mW and 42 dB respectively are obtained across the developed lasers. Through the design of the Vernier spectrum and Gapmrr, tuning of laser wavelength from 1881–1947 nm can be achieved by applying only 47.2 mW of thermal power to a single MRR. [ABSTRACT FROM AUTHOR]

The 2 $\mu \text{m}$ waveband, specifically near $1.9~\mu \text{m}$ , is an imperative resource that could possibly be exploited in future communications systems. This is due to the promising infrastructural developments at the wavelength region (hollow-core photonic bandgap fiber, thulium-doped fiber amplifier) near $1.9~\mu \text{m}$. In this work, we report the 1 $\times N$ selector switch based on Mach-Zehnder interferometers operating near the $1.9~\mu \text{m}$ wavelength region. As an elementary cell ($N $ = 2), an insertion loss as low as 1.1 dB, $\text{P}_{\pi }$ of 23 mW, 10-90% switching time of lower than 38 $\mu \text{s}$ and a crosstalk of lower than −25 dB from 1880 to 1955 nm has been determined. In order to prove scalability, the 1 $\times $ 8 switch $(N $ = 8) is demonstrated, indicating crosstalk as low as −21 dB, considering all possible switching configurations across the abovementioned wavelength region. Insertion loss levels are examined. [ABSTRACT FROM AUTHOR]

Silicon photonics at the 2 μm waveband, specifically the 1.9 μm wavelength region is strategically imperative. This is due to its infrastructural compatibility (i.e., thulium-doped fiber amplifier, hollow-core photonic bandgap fiber) in enabling communications, as well as its potential to enable a wide range of applications. While the conventional Silicon-on-Insulator platform permits passive/active functionalities, it requires stringent processing due to high-index contrast. On the other hand, SiN can serve to reduce waveguiding losses via its moderate-index contrast. In this work, by demonstrating SiN passives and Si-SiN interlayer coupler with favorable performance, we extend the Si-SiN platform to the 1.9 μm wavelength region. We report waveguide propagation loss of 2.32 dB/cm. Following, trends in radiation loss with regards to bending radius is analyzed. A high performance 3-dB power splitter with insertion loss and bandwidth of 0.05 dB and 55 nm (1935--1990 nm) respectively is introduced. Lastly, Si-SiN transition loss as low as 0.04 dB is demonstrated. [ABSTRACT FROM AUTHOR]

• The rectangular grooves are shallowly etched on the MMI waveguide to introduce the refractive-index perturbations on the MMI waveguide eigenmodes, leading to an effective refractive-index manipulation of the eigenmodes. • The refractive-index perturbation scheme provides a simple and scalable method to manipulate the four beat lengths of the two wavelengths at TE- or TM-polarization in a single waveguide via self-imaging effect, leading to a compact footprint. • The present refractive-index perturbation scheme realizes, for the first time, NIR/MIR wavelength demultiplexing and polarization independence simultaneously in an individual device. • A compact and polarization-independent wavelength diplexer for 1.31/2 μm is also realized by flexibly changing the dimensions, showing the flexibility and extensibility of our refractive-index perturbation scheme. Faced with the rapid growth of internet traffic demand, which has posed a huge challenge to the current fiber-based communications systems, expanding the telecommunications bands from traditional near-infrared (NIR) region to mid-infrared (MIR) region is emerging as an attractive solution. And on-chip wavelength division multiplexing (WDM) application for NIR/MIR wavelengths is an essential element in future optical telecommunication systems. Here, we propose a compact silicon-based polarization-independent wavelength diplexer for the NIR/MIR wavelengths of 1.55/2 μm, where multiple rectangular grooves are shallowly etched on the silicon MMI waveguide for introducing the refractive-index perturbations on the MMI waveguide eigenmodes. And this refractive-index perturbation scheme provides a simple and scalable method to manipulate the four beat lengths of the two wavelengths at TE- or TM-polarization in a single waveguide via self-imaging effect, leading to a compact footprint. By optimizing the structural parameters, both NIR/MIR wavelength demultiplexing and polarization independence, for the first time, are obtained simultaneously in the present single device. From the results, the proposed diplexer is only 21.6 μm in length, and shows a wide bandwidth of ∼ 100/120 nm around the wavelength of 1.55/2 μm for insertion loss (IL) < 1 dB and extinction ratio (ER) > 15 dB. Moreover, we also realize a compact and polarization-independent wavelength diplexer for 1.31/2 μm by flexibly changing the dimensions, showing the flexibility and extensibility of our refractive-index perturbation scheme. Besides, fabrication tolerances are analyzed and mode propagation profiles are also demonstrated. [ABSTRACT FROM AUTHOR]