We investigated low-hydrogen SiN films prepared by a low temperature (350 degrees C) PECVD method. The impact of SiH(4)/N(2) flow ratio and radio frequency power on the hydrogen content in the SiN films was studied. In this work, we demonstrated a low-loss sub-micron SiN waveguide by using the corresponding optimal SiN films. The propagation loss was found to be as low as -2.1+/-0.2 dB/cm at 1550 nm with waveguide cross-section of 700 nm x 400 nm. The results suggest that the SiN films grown by PECVD with low hydrogen can be used in photonics integrated circuits for new generation communications applications.
We propose a relay ring resonator structure which comprises multiple cascaded microring resonators, in which the drop waveguide of a microring resonator is also the input waveguide of the subsequent microring resonator, and so forth. Thus, the transmission response of the relay ring resonator structure has sharp peaks, high out-of-band rejection ratios, and long group delays. A relay ring resonator structure comprising 90 microrings is fabricated on silicon nitride wire waveguides. The simulation and experimental results are in good agreement.
A broadband silicon four-mode (de)multiplexer [(De)MUX] is proposed and experimentally demonstrated based on subwavelength gratings (SWGs)-assisted triple-waveguide couplers (TWCs), which can (de)multiplex TE0, TE1, TE2, and TE3 modes. The mode interaction is enhanced, benefitting from both the triple-waveguide coupling and subwavelength structures. The proposed four-mode (De)MUX is composed of three SWG-assisted TWCs connected by three linear tapers. The experimental results show that the 3-dB bandwidths are 100 nm, 76 nm, 90 nm, and 95 nm for the TE0, TE1, TE2, and TE3 modes, respectively. The corresponding insertion losses are 0.2, 1.8, 1.3, and 1.7 dB, and the mode crosstalks are -23.3, -17.7, -15.5, and -17.0 dB at the 1550 nm wavelength. The proposed device can work as a mode-(De)MUX compatible with wavelength division multiplexing (WDM) to increase the transmission capacity of on-chip optical interconnects.
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