Microwave properties of an inhomogeneous optically illuminated plasma in a microstrip gap

Chris D. Gamlath, David M. Benton, Martin J. Cryan

Research output: Contribution to journalArticlepeer-review


The optical illumination of a microstrip gap on a thick semiconductor substrate creates an inhomogeneous electron-hole plasma in the gap region. This allows the study of the propagation mechanism through the plasma region. This paper uses a multilayer plasma model to explain the origin of high losses in such structures. Measured results are shown up to 50 GHz and show good agreement with the simulated multilayer model. The model also allows the estimation of certain key parameters of the plasma, such as carrier density and diffusion length, which are difficult to measure by direct means. The detailed model validation performed here will enable the design of more complex microwave structures based on this architecture. While this paper focuses on monocrystalline silicon as the substrate, the model is easily adaptable to other semiconductor materials such as GaAs.

Original languageEnglish
Pages (from-to)374-383
Number of pages10
JournalIEEE Transactions on Microwave Theory and Techniques
Issue number2
Early online date19 Jan 2015
Publication statusPublished - Feb 2015

Bibliographical note

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Funding: EPSRC


  • microwave photonics
  • plasmas
  • propagation in complex media
  • RF microwave photonic devices
  • silicon


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