Fig. 9
Spectral dependencies of mode propagation constants for the tapered PCF with the SnO2 coating of thickness 0.6 μm surrounded by air; a -loss of the PCF mode, b -phase diagram. Curve 1 - quartz glass refractive index, 2 and 2′ – Reβ and Imβ of the PCF core mode, 3 and 3′ - Reβ and Imβ of TE mode of the coating, 4 and 4′ - Reβ and Imβ of TM mode of the coating. Dashed lines indicate wavelengths of phase synchronism of the PCF core and coating modes