Er³⁺: 'water-free' fluorotellurite glass waveguides written by femtosecond laser

By femtosecond laser with repetition rate of 1 kHz, central wavelength of 800 nm and pulse width of 120 fs, Type I (single line) and depressed circular cladding waveguides in Er³⁺ doped 'water-free' fluorotellurite glass are transversely written with slit shaping technology, respectively. The impact of the processing conditions on the waveguides' formation is systematically studied, and the waveguides with better guiding mode are obtained. Refractive index profile is reconstructed by intensity distribution of the near-field mode, and the largest positive refractive index change for Type I waveguide is about 1×10^-4, slightly smaller than that (1.9×10^-4) of depressed cladding waveguide. By using the scattering technique, the propagation loss of Type I waveguide is about 1.04 dB/cm. The loss of depressed cladding waveguide is less than 1.88 dB/cm by measuring insertion loss. Therefore, Er³⁺ doped 'water-free' fluorotellurite glass waveguides inscribed by femtosecond laser are promising candidates for the development of integrated laser resources.