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Copper-free chips generate robust ‘combs’ of multicoloured light

A stable ‘frequency comb’ of photons with discrete colours has been generated on a microscale chip by removing copper contaminants from the circuit.
By
  1. Mher Ghulinyan

    1. Mher Ghulinyan is in the Center for Sensors and Devices, Fondazione Bruno Kessler, Trento 38123, Italy.

  2. Martino Bernard

    1. Martino Bernard is in the Center for Sensors and Devices, Fondazione Bruno Kessler, Trento 38123, Italy.

Optical fibres, which transmit light over large distances, underpin global communications networks. An important milestone in the history of this technology was the discovery that metal-iron impurities in the fibres impair their performance, a finding that led to the development of ultra-pure optical fibres. Now, writing in Nature, Ji et al.1 apply this principle to photonic integrated circuits (PICs), which are optical devices fabricated on microscale chips. They find that contamination by copper ions can make PICs less robust, and that removing these contaminants alleviates that effect. They demonstrate this by efficiently and consistently generating light spectra called optical frequency combs, comprising discrete and regularly spaced spectral lines, from copper-ion-free materials.

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Nature 646, 806-807 (2025)

doi: https://doi.org/10.1038/d41586-025-03130-4

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The authors declare no competing interests.

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