Spectral Loss Characterization of Femtosecond Laser Written Waveguides in Glass With Application to Demultiplexing of 1300 and 1550 nm Wavelengths

Femtosecond laser written waveguides in glass were characterized across the full telecom spectrum to gain insight into waveguide loss mechanisms, and to aid in the design of a low-loss 1300/1550 nm wavelength demultiplexer. A lambda(-4) wavelength scaling of propagation loss confirms Rayleigh scattering as a principal loss mechanism. Laser exposure was optimized for generating low-loss directional couplers with high isolation between the 1300 and 1550 nm bands. Dispersive coupling in the straight and curved wavelength regions was balanced with a 1.5-fold difference in 1300 and 1550 nm beat lengths, leading to the first demonstration of 1300/1550 nm demultiplexer written with a laser. A minimum interaction length of 3.2 mm, similar to 2 dB insertion loss and channel isolations of 16.7 and 18.8 dB are reported.