Femtosecond Laser Inscription of All-Fiber Bragg Grating Based Spectrometer Using the Phase Mask Technique

Femtosecond laser pulses at two different wavelengths (400 and 800 nm) are used to fabricate highly efficient FBG-based spectrometers featuring a micropore-based internal structure. The unique cylindrical geometry of the micropores allows for strong outcoupling of light from the fiber, with relatively low polarization dependency. Bending of the fiber enables focusing of the spectrally dispersed outcoupled light on an external sensor at different locations, thereby defining an all-fiber spectrometer.