Developing Ultralow Loss, High-Power Photonics

Schematic representation of the optical measurement setup used for the characterization of microresonators and test structures. Direct laser scanning spectroscopy is carried out using a high-sensitivity photodetector (left). Microscope image of the 200-GHz-FSR ring resonators with different bus/ring gap configurations. Input/output (I/O) signal is collected via surface grating couplers (SGCs) operating in TE-polarization (right; source: H. El Dirani et al. / OSA)

Leti, an institute of CEA-Tech, has developed a silicon nitride (Si3N4) 200-mm platform for developing ultralow loss, high-power photonics in UV through mid-infrared wavelengths. Available in CEA-Leti’s SiN platform in a multi-project-wafer program, the development targets designers in integrated quantum optics, lidar, biosensing, and imaging whose projects require ultralow propagation losses and high-power handling capability.

III-V integration on Si photonics. (Source: CEA-Leti)

Announced at Photonics West 2020, this ultralow-loss SiN layer is available for multi-level photonic circuits. It can be combined with a heater layer and a silicon layer in a unique platform to integrate passive and active components, such as Mach-Zehnder interferometers, multimode interferometers, ring resonators, filters, arbitrary waveform generators, modulators and photodiodes. This ultralow-loss layer can also present a local opening for biosensing applications.

“Companies requiring III-V/SiN laser co-integration or working on integrated quantum photonics for communication and computing applications can use this unique capability to combine those ultralow-loss properties with high thickness SiN in a CMOS-compatible photonics platform,” said Eléonore Hardy, business developer at CEA-Leti. “This breakthrough process will contribute to the Quantum 2.0 revolution and will lead to photonic devices that actively create, manipulate, and read out quantum states for the emergence of quantum computing, imaging, sensing, communication, and clocks.”

Announced at Photonics West 2020, this ultralow-loss SiN layer is available for multi-level photonic circuits. (Source: CEA-Leti)

The best-in-class performance obtained with an 800-nm thick SiN layer includes a two-times reduction in propagation loss with three decibels per meter (3 dB/m) for high-confinement 1.6-µm wide strip waveguides across the S, C, and L optical-wavelength bands. CEA-Leti researchers also improved aging in the photonics devices and produced high-Q photonic microresonators with quality factors approaching 107 across the C-band and reduced feature size.

Deposition of SiN uses CEA-Leti’s high-quality twist-and-grow, low-pressure chemical vapor deposition (LPCVD) technique that deposits relatively thick, pure, and stoichiometric SiN with good thickness uniformity, unlike standard chemical vapor deposition techniques. Furthermore, a multistep chemical-physical annealing smoothed the sidewall roughness of SiN waveguides, which further decreased propagation losses. (Source: CEA-Leti)

Link: Leti Workshop “Disruptive photonics concepts for new applications & markets” at the San Francisco W Hotel, Feb. 5th 2020 during Photonics West 2020Photonics West 2020. CEA-Leti, Grenoble, France

Reference: H. El Dirani et al.: Ultralow-loss tightly confining Si3N4 waveguides and high-Q microresonators, Optics Express 27(21), 30726-30740 (2019); DOI: 10.1364/oe.27.030726

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