Mid-infrared channel waveguides in RbPb2Cl5 crystal inscribed by femtosecond laser pulses

Tubular cladding waveguide was inscribed in crystal volume by a femtosecond laser operating at 0.8 µm. The waveguide sustains a single leaking mode at wavelength of 3.39 µm. Propagation losses were investigated experimentally and theoretically at wavelengths of 1.58 µm and 3.39 µm. Measured losses were found to be as low as 1.4 dB/cm at 1.58 µm and 5.1 dB/cm at 3.39 µm. Complex propagation constants for leaking modes were obtained by numerical mode analysis. It was found, that mode leakage is a major factor of losses at wavelength of 3.39 µm.