Cao, Y., Sahin, E., Choi, J. W., Xing, P., Chen, G. F. R., Ng, D. K. T., Eggleton, B. J., & Tan, D. T. H. (2021). Thermo-optically tunable spectral broadening in a nonlinear ultra-silicon-rich nitride Bragg grating. Photonics Research, 9(4), 596. https://doi.org/10.1364/prj.411073
Abstract:
Spectral tunability methods used in optical communications and signal processing leveraging optical, electrical, and acousto-optic effects typically involve spectral truncation that results in energy loss. Here we demonstrate temperature tunable spectral broadening using a nonlinear ultra-silicon-rich nitride device consisting of a 3-mm-long cladding-modulated Bragg grating and a 7-mm-long nonlinear channel waveguide. By operating at frequencies close to the grating band edge, in an apodized Bragg grating, we access strong grating-induced dispersion while maintaining low losses and high transmissivity. We further exploit the redshift in the Bragg grating stopband due to the thermo-optic effect to achieve tunable dispersion, leading to varying degrees of soliton-effect compression and self-phase-modulation-induced spectral broadening. We observe an increase in the bandwidth of the output pulse spectrum from 69 to 106 nm as temperature decreases from 70°C to 25°C, in good agreement with simulated results using the generalized nonlinear Schrödinger equation. The demonstrated approach provides a new avenue to achieve on-chip laser spectral tuning without loss in pulse energy.
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Funding Info:
This research / project is supported by the National Research Foundation - Competitive Research Grant
Grant Reference no. : NRF-CRP18- 2017-03
This research / project is supported by the Ministry of Education - ACRF Tier 2
Grant Reference no. : N.A