Microwave photonic notch filter using SBS in silicon nitride waveguide. (a) Schematic of the experimental setup to demonstrate the MWP notch filter. The input RF signal generated from a vector network analyzer (VNA) is modulated onto the optical probe using an in-phase quadrature (IQ) modulator. An optical pump is amplified using an erbium-doped fiber amplifier (EDFA) and then injected to 1.4 µm-wide, 50 cm-long SDS waveguide with 0.16 m −1 W −1 SBS gain coefficient and 0.2 dB/cm propagation loss. An optical bandpass filter (BPF) was used before photodetection (PD) to remove pump backreflection. Hybrid: 90 o RF hybrid coupler, PC: fiber polarization controller. (b) RF and optical spectra at different points of signal path: (I) Input RF signal. (II) Asymmetric dual sideband phase modulated signal generated from the IQ modulator. The RF sidebands are out of phase and their amplitude ratio is controlled to match the SBS gain magnitude generated from the silicon nitride waveguide. (III) SBS gain from the silicon nitride waveguide is used equalize the sideband amplitue at the intended RF notch frequency. (IV) At the detector the mixing products between sidebands and the optical carrier leads to a notch filter due to RF cancellation. (c) The measured SBS gain when the IQ modulator is set to single-sideband modulation. (d) The measured high-rejection RF notch filter response which was obtained using only 0.4 dB of on-chip SBS gain. The 3-dB bandwidth of the filter is 400 MHz and the rejection is 30 dB.

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... waveguide. Considering the limited SBS gain from the waveguides, the RF cancellation notch filter [7,65,66], a scheme that relies on synthesizing destructive RF interference due to careful tailoring of phase and amplitude of RF modulated sidebands, would be an ideal choice. A simplified schematic of the RF photonic notch filter is diagrammed in Fig. 4 (a). A key component in this filter is the in-phase quadrature (IQ) modulator (also known as the dual-parallel Mach-Zehnder modulator) used often synthesizing the RF moudulates sidebands with the correct phase and amplitude relations prior to the narrowband processing using the SBS gain resonance. The details of the RF notch filter ...

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... quadrature (IQ) modulator (also known as the dual-parallel Mach-Zehnder modulator) used often synthesizing the RF moudulates sidebands with the correct phase and amplitude relations prior to the narrowband processing using the SBS gain resonance. The details of the RF notch filter experiments can be found in Methods and Supplementary Note B. Fig. 4 (b) shows the working principle of the RF notch filter. The RF input (I) is modulated onto the probe laser using the IQ modulator creating an asymmetric dual sideband modulation, with the sidebands in antiphase (II). The on-chip SBS interaction with the probe light then amplifies a spectral region of the lower sideband (III) making the ...

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... first step in creating the notch filter is to characterize the peak SBS gain exhibited from the waveguide. We achieved this by tuning the IQ modulator to create a single sideband modulation with optical carrier spectrum. The measured SBS gain response obtained from the vector network analyzer (VNA) is depicted in Fig. 4 (c), showing a peak gain of approximately 0.4 dB. We then tuned the IQ modulator to synthesize the asymmetric dual sideband modulation with 0.4 dB difference in the two sidebands amplitude. The resulting RF notch filter response is depicted in Fig. 4 (d). The peak rejection of the filter was measured to be 30 dB and the filter's 3 dB ...

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... The measured SBS gain response obtained from the vector network analyzer (VNA) is depicted in Fig. 4 (c), showing a peak gain of approximately 0.4 dB. We then tuned the IQ modulator to synthesize the asymmetric dual sideband modulation with 0.4 dB difference in the two sidebands amplitude. The resulting RF notch filter response is depicted in Fig. 4 (d). The peak rejection of the filter was measured to be 30 dB and the filter's 3 dB bandwidth was 400 MHz. This result constitutes the first ever signal processing demonstration of SBS in silicon nitride waveguides and points towards the potential of unlocking unique Brillouin signal processing capabilities in a mature silicon nitride ...

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... candidates from the gene pool to increase the variety. Finally, both parents and kids and the new candidates would enter the next round evolution. Fig. S3 shows the SBS gain of all simulated structures with genetic algorithm. The SBS gain tends to increases with the Brillouin shift frequency. The highest gain is around 1.2 m −1 W −1 at 14 GHz. Fig. S4 shows the normalized electric fields, normalized acoustic displacement fields, and gain profiles of some selected geometries that are labelled (a)-(f) in Fig. S3. As the SBS gain increases, the gain profile also becomes sharper. From the acoustic displacement field, we can also find that the acoustic field is stronger and more ...

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... applying equation 6 on the different gain parameters and frequency shifts of the SBS waveguides a to f selected in supplementary A and shown in Fig. S4, with the length such that Ω/2π = F SR ν , we find a relation as given in Fig. S6 with the details given in Table S5. The group indices shown in Table S5 have been calculated for the different waveguides via the method given in [74] and are used to convert the target FSR to the length of the resonator by F SR = c ngL . Figure S6. The ...

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... S5. The group indices shown in Table S5 have been calculated for the different waveguides via the method given in [74] and are used to convert the target FSR to the length of the resonator by F SR = c ngL . Figure S6. The SBS lasing threshold calculated by equation 6 using the parameters from Table S5 for the waveguide geometries a to f given in Fig. S4 for a loss ranging from 0.2 to 0.005 dB/cm. The dotted lines give the losses 0.1 dB/cm, 0.05 dB/cm, and 0.01 dB/cm, for which the threshold powers are shown in Table ...