Fig. 2: Experimental setup.
From: Absorption-induced transmission in plasma microphotonics
a Micrograph of the plasma’s glow taken using a visible camera. b Micrograph of the optical resonance taken using a camera sensitive to 1.55 μm wavelength. The five spots at the top part of the bubble indicate the transverse cross section of the 5th order transverse mode, as indicated by residual forward scattering. c Numerical calculation of the 5th order polar mode reveals 4% penetration of the resonating power into the plasma-containing region. d Drawing of the experimental system. A silica capillary tube is filled with argon. Connected with a high voltage source, two electrodes (two orange cones) are inserted into the silica capillary tube to active plasma. Laser light can be coupled into the bubble resonator through a tapered fibre. The red circle represents the optical mode. On the other side of the fibre, an infrared photodiode (PD) is used to monitor the transmission. A visible photodiode is used to monitor plasma luminescence. A spectrometer is used for plasma emission spectroscopy. A visible camera is used for inspecting plasma luminescence and an infrared camera is used for inspecting the infrared resonance.
