The fabrication processes of silicon nitride photonic devices used in foundries require low temperature deposition, which typically leads to high propagation losses. Here, we show that propagation loss as low as 0.42 dB/cm can be achieved using foundry compatible processes by solely reducing waveguide surface roughness. By post-processing the fabricated devices using rapid thermal anneal (RTA) and furnace anneal, we achieve propagation losses down to 0.28 dB/cm and 0.06 dB/cm, respectively. These low losses are comparable to the conventional devices using high temperature, high-stress low-pressure chemical vapor deposition (LPCVD) films. We also tune the dispersion of the devices, and proved that these devices can be used for linear and nonlinear applications. Low threshold parametric oscillation, broadband frequency combs and narrow-linewidth laser are demonstrated. Our work demonstrates the feasibility of scalable photonic systems based on foundries.
Max Planck Institute for the Science of Light（马克斯·普朗克光科学研究所）；Friedrich-Alexander Universität Erlangen-Nürnberg（埃尔朗根-纽伦堡大学）；Technical University of Denmark（丹麦技术大学）；John A. Paulson School of Engineering and Applied Sciences, Harvard University（哈佛大学约翰·A·保尔森工程与应用科学学院）；Massachusetts Institute of Technology（麻省理工学院）；The Chinese University of Hong Kong, Shenzhen（香港中文大学（深圳））；SPINS Photonics Inc（SPINS光子有限公司）
The foundry development of integrated photonics has revolutionized today's optical interconnect and datacenters. Over the last decade, we have witnessed the rising of silicon nitride (Si$_3$N$_4$) integrated photonics, which is currently transferring from laboratory research to foundry manufacturing. The development and transition are triggered by the ultimate need of low optical loss offered by Si$_3$N$_4$, which is beyond the reach of silicon and III-V semiconductors. Combined with modest Kerr nonlinearity, tight optical confinement and dispersion engineering, Si$_3$N$_4$ has today become th…
We demonstrate dispersion engineering of integrated silicon nitride based ring resonators through conformal coating with hafnium dioxide deposited on top of the structures via atomic layer deposition (ALD). Both, magnitude and bandwidth of anomalous dispersion can be significantly increased. All results are confirmed by high resolution frequency-comb-assisted-diode-laser spectroscopy and are in very good agreement with the simulated modification of the mode spectrum.
High-quality ultra-thin films of niobium nitride (NbN) are developed by plasma-enhanced atomic layer deposition (PEALD) technique. Superconducting nanowire single-photon detectors (SNSPDs) patterned from this material exhibit high switching currents and saturated internal efficiencies over a broad bias range at 1550 nm telecommunication wavelength. Statistical analyses on hundreds of fabricated devices show near-unity throughput yield due to exceptional homogeneity of the films. The ALD-NbN material represents an ideal superconducting material for fabricating large single-photon detector array…
Low-loss photonic integrated circuits (PIC) and microresonators have enabled novel applications ranging from narrow-linewidth lasers, microwave photonics, to chip-scale optical frequency combs and quantum frequency conversion. To translate these results into a widespread technology, attaining ultralow optical losses with established foundry manufacturing is critical. Recent advances in fabrication of integrated Si3N4 photonics have shown that ultralow-loss, dispersion-engineered microresonators can be attained at die-level throughput. For emerging nonlinear applications such as integrated trav…
We demonstrate high optical quality factors in aluminum nitride (AlN) photonic crystal nanobeam cavities. Suspended AlN photonic crystal nanobeams are fabricated in sputter-deposited AlN-on-insulator substrates using a self-protecting release process. Employing one-dimensional photonic crystal cavities coupled to integrated optical circuits we measure quality factors up to 146,000. By varying the waveguide-cavity coupling gap, extinction ratios in excess of 15 dB are obtained. Our results open the door for integrated photonic bandgap structures made from a low loss, wide-transparency, nonlinea…
We demonstrate wideband integrated photonic circuits in sputter-deposited aluminum nitride (AlN) thin films. At both near-infrared and visible wavelengths, we achieve low propagation loss in integrated waveguides and realize high-quality optical resonators. In the telecoms C-band (1520-1580 nm), we obtain the highest optical Q factor of 440,000. Critical coupled devices show extinction ratio above 30 dB. For visible wavelengths (around 770 nm), intrinsic quality factors in excess of 30,000 is demonstrated. Our work illustrates the potential of AlN as a low loss material for wideband optical ap…
We present experimental results on second-harmonic generation in non-stoichiometric, silicon-rich nitride (SRN) films. The as-deposited film presents a second-order nonlinear coefficient, or \c{hi}(2), as high as 8pm/V. This value can be widely tuned using the electric field induced second harmonic effect (EFISH), and a maximum value of 22.7pm/V was achieved with this technique. We further illustrate that the second-order nonlinear coefficient exhibited by these films can be highly dispersive in nature, and requires further study and analysis to evaluate their viability for in-waveguide applic…
We report and characterize low-temperature, plasma-deposited deuterated silicon nitride thin films for nonlinear integrated photonics. With a peak processing temperature less than 300$^\circ$C, it is back-end compatible with pre-processed CMOS substrates. We achieve microresonators with a quality factor of up to $1.6\times 10^6 $ at 1552 nm, and $>1.2\times 10^6$ throughout $λ$ = 1510 -- 1600 nm, without annealing or stress management. We then demonstrate the immediate utility of this platform in nonlinear photonics by generating a 1 THz free spectral range, 900-nm-bandwidth modulation-instabi…
We demonstrate a silicon nitride trench waveguide deposited with bowtie antennas for plasmonic enhanced optical trapping. The sub-micron silicon nitride trench waveguides were fabricated with conventional optical lithography in a low cost manner. The waveguides embrace not only low propagation loss and high nonlinearity, but also the inborn merits of combining micro-fluidic channel and waveguide together. Analyte contained in the trapezoidal trench channel can interact with the evanescent field from the waveguide beneath. The evanescent field can be further enhanced by plasmonic nanostructures…
Optomechanical SiN nano-oscillators in high-finesse Fabry-Perot cavities can be used to investigate the interaction between mechanical and optical degree of freedom for ultra-sensitive metrology and fundamental quantum mechanical studies. In this work we present a nano-oscillator made of a high-stress round-shaped SiN membrane with an integrated on-chip 3D seismic filter properly designed to reduce mechanical losses. This oscillator works in the 200 kHz - 5 MHz range and features a mechanical quality factor of $Q\simeq10^7$ and a Q-frequency product in excess of $6.2 \times 10^{12}$ Hz at room…
Integrated photonics plays a central role in modern science and technology, enabling experiments from nonlinear science to quantum information, ultraprecise measurements and sensing, and advanced applications like data communication and signal processing. Optical materials with favorable properties are essential for nanofabrication of integrated-photonics devices. Here we describe a material for integrated nonlinear photonics, tantalum pentoxide (Ta$_2$O$_5$, hereafter tantala), which offers low intrinsic material stress, low optical loss, and efficient access to Kerr-nonlinear processes. We u…
The aim of the study is to develop ultra-compact structures enabling an efficient conversion of single high energy photon (UV) to two lower energy photons (IR). The proposed structure combines rare-earths doped thin layer allowing the down-conversion process with a photonic crystal (PhC), in order to control and enhance the down-conversion using optical resonances. On the top of the rare-earths doped layer, a silicon nitride (SiN) 2D planar PhC is synthesized. For that, SiN is first deposited by PECVD. After holographic lithography and reactive ion etching, a periodic square lattice of holes i…
