Next-generation passive optical networks require integrated, polarization-insensitive wavelength-division multiplexing solutions, for which the recently emerging low-loss silicon nitride nanophotonic platforms hold great potential. A novel polarization-insensitive arrayed waveguide grating (AWG) built with silicon nitride waveguides is presented in this Letter. Polarization insensitivity is obtained when both the channel spacing and the center wavelength of the two orthogonal polarization states (i.e., the TE and TM waveguide modes) are simultaneously aligned. In our design, the channel spacing alignment between the polarization states is obtained by optimizing the geometry of the arrayed waveguides, whereas the central wavelength polarization insensitivity is obtained by splitting the two polarization states and adjusting their angle of incidence at the input star coupler to compensate for the polarization mode dispersion of the AWG. A 100 GHz 1×8 wavelength-division multiplexer with crosstalk levels below -16 dB is demonstrated experimentally.

We present a low-loss, compact, polarization insensitive 3-dB optical power-splitter for submicron silicon waveguides. The splitter is optimized over a broad wavelength span ranging from 1300 to 1700 nm through finite difference time domain simulations. The splitter junction footprint is only 1.8 × 1.3 μm, which is smaller than previously reported broadband multimode junction splitters. Furthermore, the demonstrated device overcomes the fabrication limitations of previous splitters while maintaining a compact size without any sharp angles. The device was fabricated using electron beam lithography. The experimental results show a small insertion loss of less than 0.3 dB for both the TE and TM polarizations.

We present a 1 × 3 optical switch based on a translational microelectromechanical system (MEMS) platform with integrated silicon nitride (SiN) photonic waveguides. The fabricated devices demonstrate efficient optical signal transmission between fixed and suspended movable waveguides. We report a minimum average insertion loss of 4.64 dB and a maximum average insertion loss of 5.83 dB in different switching positions over a wavelength range of 1530 nm to 1580 nm. The unique gap closing mechanism reduces the average insertion loss across two air gaps by a maximum of 7.89 dB. The optical switch was fabricated using a custom microfabrication process developed by AEPONYX Inc. This microfabrication process integrates SiN waveguides with silicon-on-insulator based MEMS devices with minimal stress related deformation of the MEMS platform.

While 3-D microelectromechanical systems (MEMS) allow switching between a large number of ports in optical telecommunication networks, the development of such systems often suffers from design, fabrication and packaging constraints due to the complex structures, the wafer bonding processes involved, and the tight alignment tolerances between different components. In this work, we present a 2-D translational MEMS platform capable of highly efficient planar optical switching through integration with silicon nitride (SiN) based optical waveguides. The discrete lateral displacement provided by simple parallel plate actuators on opposite sides of the central platform enables switching between different input and output waveguides. The proposed structure can displace the central platform by 3.37 µm in two directions at an actuation voltage of 65 V. Additionally, the parallel plate actuator designed for closing completely the 4.26 µm air gap between the fixed and moving waveguides operates at just 50 V. Eigenmode expansion analysis shows over 99% butt-coupling efficiency the between the SiN waveguides when the gap is closed. Also, 2.5 finite-difference time-domain analysis demonstrates zero cross talk between two parallel SiN waveguides across the length of the platform for a 3.5 µm separation between adjacent waveguides enabling multiple waveguide configuration onto the platform. Different MEMS designs were simulated using static structural analysis in ANSYS. These designs were fabricated with a custom process by AEPONYX Inc. (Montreal, QC, Canada) and through the PiezoMUMPs process of MEMSCAP (Durham, NC, USA).

Photothermal effects have been pointed out as prominent sources of forces in optomechanical systems, competing with the standard radiation pressure interactions. In this article, we derive a novel and accurate model for the prediction of photothermal forces and establish how some previous proposals can be complemented to yield precise results. As a proof-of-concept, we perform numerical and experimental tests on GaAs microdisk cavities and obtain striking agreement with our framework, revealing the importance of considering surface photothermal forces and the effects of multiple thermal modes in microphotonic devices.

Integrated photonic devices made of silicon nitride, which can be integrated with silicon-on-insulator and III-V platforms, are expected to drive the expansion of silicon photonics technology. However, the relatively low refractive index contrast of silicon nitride is often considered a limitation for creating compact and efficient devices. Here, we present three freeform silicon nitride devices—a coarse wavelength-division multiplexer, a five-mode mode division multiplexer, and a polarization beam splitter—while systematically benchmarking both the design capability and the fabrication repeatability and robustness of inverse-designed components. We demonstrate up to a 1200× reduction in footprint while maintaining relatively large minimum feature sizes of up to 160 nm, showing that inverse-designed silicon nitride devices can be as compact as their silicon counterparts. These results enable high-density integration in silicon nitride photonics and pave the way for multidimensional data transmission and quantum applications, as the inverse design technique can be applied to different silicon nitride thicknesses and is potentially extendable to other low- and mid-index contrast platforms.