94 GHz microplasma sustained by a photonic crystal. (19th November 2021)

• Record Type: Journal Article
• Authors: Hopwood, Jeffrey
• Is Part Of: Plasma sources science & technology. Volume 30:Number 11(2021)
• Publication Date: 2021-11-19
• Subjects: photonics -- microplasma -- millimeter waves -- plasma spectroscopy; Plasma (Ionized gases) -- Periodicals; 530.44
• DOI: 10.1088/1361-6595/ac3213
• Languages: English
• ISSNs: 0963-0252

Abstract

Abstract: A photonic crystal (PhC) with a single vacancy sustains an argon microplasma at 94 GHz. The PhC consists of a 7 × 13 array of small alumina rods, each 250 μ m in radius. The PhC has a forbidden bandgap from 70–105 GHz. The vacancy creates an internal electromagnetic resonance at 94 GHz that intensifies the electric field of an incident wave to 5 × 10 5 V m −1 . Breakdown of low-pressure argon gas (80 mbar) occurs and forms a stable, ellipsoidal plasma inside the crystal. The central core of the microplasma is probed using a 200 μ m optical fiber inserted into the PhC. The rotational temperature of the CH molecule is estimated from a numerical fit of the plasma emission and is found to increase from 450–650 K with both pressure (200–1000 mbar) and incident wave power (100 mW–1100 mW). Under these conditions, the electron density increases with both power and pressure from 0.5–1.5 × 10 20 m −3 . This plasma density range brackets the electron plasma frequency at 94 GHz. The results are compared with a similar microplasma operating at 44 GHz.