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An ultraviolet chip modulator passes 40 gigahertz in laboratory tests

Researchers demonstrated an integrated device that controls ultraviolet light with electrical signals. The peer-reviewed laboratory experiment used a lithium tantalate chip at a wavelength of 375 nanometres and measured bandwidth beyond 40 gigahertz. The result concerns a component for future optical systems; substantial light losses still separate it from complete deployed applications.

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A two-arm optical chip on pale ceramic, with optical fibres aligned at opposite ends and an electrical probe touching a gold contact pad.

An electrical signal changes ultraviolet intensity

A chip-scale component has demonstrated rapid electrical control of ultraviolet light in a peer-reviewed laboratory experiment. Built on thin-film lithium tantalate, the modulator operated at 375 nanometres. Its measured electrical-to-optical-to-electrical bandwidth exceeded 40 gigahertz. The result extends integrated active light control into a wavelength range where materials and optical losses have complicated miniaturisation.[1], [2]

The device uses an electro-optic effect: an electric field changes the material’s refractive index. Light takes two paths through a Mach–Zehnder interferometer, an optical arrangement that splits and then recombines a beam. A difference in the phase accumulated along the arms changes the intensity at the output when they meet again.[1]

Fast ultraviolet modulation has generally depended on bulky crystals and high-voltage electronics. Some existing chip approaches instead rely on heating or mechanical movement, which can affect neighbouring circuits or limit switching speed.[1], [2]

A short active region faces optical losses

The active region was 200 micrometres long within a complete device measuring 1.16 millimetres. Its half-wave voltage–length product, a measure combining the voltage required for modulation with active length, was 85 millivolt centimetres. The researchers measured propagation loss of 7.2 decibels per centimetre in the single-mode waveguide and insertion loss of 2.8 decibels for the modulator.[1]

Coupling light between an optical fibre and the chip cost 9.7 ± 0.3 decibels per facet, a separate loss from insertion loss. Scattering and material defects remain important at short wavelengths. Electron microscopy and atomic-force microscopy examined the geometry and surface roughness of the fabricated structures.[1]

Compact clocks and quantum systems remain applications to develop

The interferometer layout was selected to limit sensitivity to temperature changes and fabrication variation compared with narrow resonators. Atomic clocks, quantum information processing and ultraviolet communications are potential applications of integrated modulation. The experiment demonstrates a laboratory component; complete deployed systems and commercial adoption remain outside its results. Further development is directed at reducing optical losses.[1]

References

  1. News sourceNature CommunicationsLithium tantalate chip rapidly modulates ultraviolet light↩1↩2↩3↩4↩5↩6
  2. News sourceEntech OnlineLithium tantalate chip rapidly modulates ultraviolet light↩1↩2
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