Figure 5
From: Negative-index gratings formed by femtosecond laser overexposure and thermal regeneration
Evolution of transmission loss at dip wavelength, λD during thermal annealing.
Upper panel: evolution of two orthogonal polarization modes (TE, TM) of the highly polarization dependant phase-shifted FBG (P-PSFBG). Lower panel: evoluation of original type I-IR fibre Bragg grating (FBG) during the temperature rise and the long-term annealing at 800 °C. The two gratings were inscribed with the same pulse energy of 240 μJ, but with different exposure times, 210 s and 30 s, respectively.
