Abstract: The analytical solution of the diffraction spectra of waveguide grating is deduced. Then the influence of the thickness of the waveguide and the period of the grating on the diffraction spectra is studied by using the analytical solution. It is found that the resonance wavelength moves to the red with increasing the period of the grating （the thickness of the waveguide） , the tuning rate is measured to be about 1 nm （0. 125 nm） spectral shift per 1 nm increasing in grating period （the waveguide thickness）. The theoretical analysis is in well agreement with the experimental result. Some potential applications of the waveguide grating in the laser cavity and the highly directional emission device are also discussed.

Key words: grating, waveguide, coupling output, diffraction spectra