3P2 state of rare-earth-metal ytterbium atoms is a very important meta-stable state with long lifetime.In order to study probability of 1S0→3P2 transition as a clock transition for ytterbium atoms

state preparation has to be realized with help of 507 nm light field.In order to obtain second harmonic generation（SHG） of 507 nm with a waveguide periodically poled lithium niobate nonlinear crystal（WG PPLN）

a simple coupling method with single short-focus lens was adopted.Experimental results show that we can get output power of 86.5 μW at 507nm with single lens（f=20 mm） coupling scheme

the input power of fundamental laser at 1 014 nm is around 58.2 mW.With the method of lens coupling

the relation between the output power and phase matching temperature was given.By contrast

we conducted the coupling of the WG PPLN with bare fiber

as the usual way used by other groups.It shows that the higher doubling efficiency with single lens is obtained compared with that with a fiber case.