Advancements in quantum technologies over the last decade have the potential to revolutionize sensing, communication, and computation. Quantum applications do not rely on a single preferred material platform, as each has strengths and limitations. This is particularly relevant in integrated quantum photonics, which manipulates photon states through integrated optical circuits.
Unlike traditional electronic circuits, Photonic Integrated Circuits (PICs) leverage the power of light to enable faster, more efficient data transmission with minimal energy consumption. Their development marks a critical step towards meeting the growing demand for high-speed communication and advanced optical technologies.
While the potential of Photonic Integrated Circuits (PICs) is immense, their development comes with unique challenges, including fabrication complexity and material limitations. However, these obstacles also present opportunities for innovation and collaboration across industries.
In this context, silicon nitride (SiN) is gaining prominence for its exceptional optical properties. It utilizes CMOS technology for fabrication, enabling low propagation loss in compact designs. Its wide optical bandgap and resistance to two-photon absorption (TPA) make SiN a strong candidate for quantum applications. Furthermore, its broad spectral range allows compatibility with single-photon sources and detectors in the visible spectrum, where silicon falls short.
Several studies performed by Lorenzo Pavesi´s research group at Universidad di Trento explore state-of-the-art SiN-based photonic integrated circuits (PICs) and their potential in classical and quantum applications, including waveguide crossings, multimode interferometers (MMIs), photon filters, Mach-Zehnder interferometers (aMZIs), and micro-ring resonators within the 650–850 nm spectrum. It also delves into the design, fabrication, and both theoretical and experimental aspects of these components.
SiN Integrated Photonic Components in the Visible to Near-Infrared Spectral Region
This study highlights silicon nitride (SiN) as an ideal material for developing quantum photonic integrated circuits (QPICs) within the visible-to-near-infrared range. Various integrated SiN-based building blocks have been designed, fabricated, and tested, showcasing state-of-the-art performance with low insertion losses and high efficiency.
Silicon nitride (SiN) PICs were fabricated with precise processes, including LPCVD deposition and tailored etching techniques, to achieve single-mode waveguides at 750 nm. Optical characterization heavily relied on FYLA SCT500 supercontinuum laser as the light source. This enabled the measurement of a broad spectral response (650–850 nm) with high precision [Figure 1]. Input polarization was controlled using achromatic wave plates, while output spectra were analyzed with a high-resolution Optical Spectrum Analyzer (OSA). Key performance metrics, such as propagation losses (PLs) and coupling losses (CLs), were quantified using the cut-back method, highlighting PLs as low as 2.4 dB/cm (TE) and 1.6 dB/cm (TM) near 750 nm.
The setup, with optimized tapering and filtering designs, ensured reliable measurements and minimized stray light, demonstrating the vital role of FYLA´s supercontinuum laser in characterizing optical performance.
Furthermore, key components include multimode interferometers (MMIs), which feature remarkable spectral balance across a wide bandwidth and are suitable for Mach-Zehnder interferometers (MZIs). These MZIs effectively enable wavelength selectors and integrated filters, achieving high rejection levels in cascaded configurations [Figure 2].
Additionally, SiN micro-ring resonators demonstrate a high-quality factor (4.5 × 10⁴) combined with compact dimensions, supporting its potential for quantum applications [Figure 3].
Future developments aim to integrate quantum photon sources and single-photon detectors to complete SiN-based QPIC systems around 750 nm.
How FYLA´s Supercontinuum Lasers are Paving the Way Toward the Next Generation of Photonic Integrated Circuits
The supercontinuum laser is a key tool for optical characterization in integrated photonics. Its broad spectral range, spanning from visible to near-infrared wavelengths, enables precise measurements of waveguide performance and device functionality.
By coupling this laser source with photonic chips, high-resolution spectral responses can be obtained using optical spectrum analyzers, ensuring an accurate evaluation of insertion losses, propagation losses, and polarization behavior. This technology is instrumental in advancing the development and optimization of integrated photonic circuits. In this scope, we propose the use of the Iceblink and the Horizon supercontinuum lasers for specific reasons:
- Wide Spectral Range: FYLA´s supercontinuum laser’s spectrum from 450 to 2300 nm covers a broad wavelength range, enabling the characterization of diverse photonic structures across visible, near-infrared, and mid-infrared regions.
- High Average Power: With over 3 W of total power, the laser provides sufficient intensity for precise measurements, ensuring reliable data acquisition even in demanding optical setups.
- High Repetition Rate: The 80 MHz repetition rate allows for rapid data collection, facilitating real-time analysis of photonic integrated chips and improving the efficiency of characterization processes.
- Ultrafast Pulses: Pulse durations of less than 10 picoseconds enable high temporal resolution, critical for studying ultrafast phenomena and non-linear optical effects in integrated photonic devices.
- Exceptional Stability: Power stability with a standard deviation below 0.5% ensures consistent and repeatable results, which are essential for high-precision optical characterization.
