A continuous-wave distributed feedback diode laser emitting at $976\mathrm{nm}$ was frequency doubled by the use of a periodically poled lithium niobate waveguide crystal with a channel size of $3\mu \mathrm{m}\times 5\mu \mathrm{m}$ and an interaction length of $10\mathrm{mm}$ . A laser to waveguide coupling efficiency of 75% could be achieved resulting in $304\mathrm{mW}$ of incident infrared light inside the waveguide. Blue laser light emission of $159\mathrm{mW}$ at $488\mathrm{nm}$ has been generated, which equals to a conversion efficiency of 52%. The resulting wall plug efficiency was 7.4%.