Control of average wavelength-converted power and/or wavelength converted pulse energy is described. One or more seed pulses may be generated and amplified with an optical amplifier to produce one or more amplified pulses. The amplified pulses may be wavelength converted to produce one or more wavelength converted pulses characterized by an average wavelength-converted power or pulse energy. Wavelength-converted power or pulse energy may be controlled by adjusting wavelength conversion efficiency without substantially changing the amplified power or pulse energy. Average wavelength-converted power may be controlled over a time scale comparable to a pulse period of the amplified pulses without adjusting an average power of the amplified pulses over the time scale comparable to a pulse period of the amplified pulses. A wavelength-converted optical system, may comprise a seed source, an optical amplifier optically coupled to the seed source, a wavelength converter optically coupled to the optical amplifier; and a controller operably coupled to the seed source and/or optical amplifier and/or wavelength converter. The controller may include logic adapted to control an average wavelength-converted power of an output of the wavelength converter over a time scale comparable to a pulse period of amplified pulses from the optical amplifier without adjusting an average power of the amplified pulses over that time scale. Alternatively, the controller logic may be adapted to control wavelength-converted pulse energy by adjusting the wavelength conversion efficiency without substantially changing the pulse energy of the amplified pulses.