An optical apparatus that includes an optical source that generates a first optical pulse with a first optical wavelength. The optical apparatus also includes an optical amplifier that outputs an amplified pulse. The optical apparatus also includes a first waveguide that is connected to the optical amplifier and a second waveguide. Wherein the second waveguide converts the energy of the amplified pulse into energy of a second pulse that has a second optical wavelength different from the first optical wavelength. Wherein, the following equation is satisfied: L_min≦L≦π/γP. In which a length of the first waveguide is L, a nonlinear coefficient of the first waveguide is γ, a peak power of the amplified pulse as it is received by the first waveguide is P, and a minimum length of the first waveguide is L_min or L is equal to zero.