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Nanophotonic phase noise filter in silicon


Narrow-linewidth light sources have far-reaching applications from communication1 to metrology2,3,4. Benchtop linewidth reduction methods such as feedback5,6 and feed-forward7,8 schemes have been used to reduce the linewidth of lasers. The feedback scheme typically has a limited bandwidth and depends on the laser characteristics and the feed-forward scheme is highly sensitive to gain and delay mismatches. Here, we report the demonstration of an integrated nanophotonic phase noise filter, which can be placed after a low-cost laser to significantly suppress its phase noise independent of the light source. The hybrid-integrated electronic–photonic system measures and suppresses the phase noise of the input light using an electronic–photonic loop without interacting with the light source. Using the integrated phase noise filter, laser linewidth reduction from 2.55 MHz to 4 kHz and from 200 kHz to 320 Hz is demonstrated. The silicon photonic and complementary metal–oxide–semiconductor (CMOS) electronic chips were hybrid-integrated within a footprint of 3 mm2.

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Fig. 1: Phase noise filter.
Fig. 2: SSB intensity modulator.
Fig. 3: Frequency noise discriminator.
Fig. 4: The implemented phase noise filter.
Fig. 5: Measurement set-up and results.

Data availability

The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.


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This work was supported by DARPA under contract number HR0011-19-2-0013. The CMOS chip fabrication was supported by MOSIS Services.

Author information




M.H.I. and F.A. conceived the project idea. M.H.I. designed, simulated and laid out the integrated electronic and photonic circuits and conducted measurements. F.A. directed and supervised the project. M.H.I. and F.A. wrote the manuscript.

Corresponding author

Correspondence to Firooz Aflatouni.

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The authors declare no competing interests.

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Extended data

Extended Data Fig. 1 Effect of SSB non-idealities on linewidth reduction performance.

Simulated linewidth reduction efficiency, 𝜂, representing the effect of SSB non-idealities on linewidth reduction performance.

Supplementary information

Supplementary Information

Supplementary Notes 1–8, Figs. 1–8 and Table 1.

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Idjadi, M.H., Aflatouni, F. Nanophotonic phase noise filter in silicon. Nat. Photonics 14, 234–239 (2020).

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