Transmission spectra dependence on the grating lengths of long period fiber grating fabricated by 800nm femtosecond laser pulses

Abstract

Femtosecond laser pulses with ultrashort time duration and ultrahigh peak power can cause the refractive index change in transparent materials and micron scale machining precision. Long period fiber gratings (LPFGs) with different grating lengths in the standard single mode fiber are fabricated. Using laser direct writing method, Femtosecond laser pulses with pulse width of 200 fs at a center wavelength of 800 nm in air is applied as laser source. The transmission spectra are studied in the range of 1510 nm to 1610 nm. The loss peak of 1552 nm, the transmission loss of 16 dB and the FWHM of 20 nm are obtained with the period of LPFG of 400 μm. According to the theory of mode field coupling for long period grating, transmission spectra of LPFGs are numerically simulated depending on the grating length.