Lasers are provided to deliver a wide variety of wavelengths at variable pulse energy. A laser cavity is formed between a first and second reflective surface. A lasing medium is located within cavity which lases at a preselected fundamental frequency. One or more nonlinear crystals are provided in optical communication with the lasing crystal to produce a secondary beam having a different frequency than the fundamental beam. A modulator is provided to control the pulse energy of the secondary beam. Desirably the secondary beam is a harmonic beam for example a second, third, fourth or fifth harmonic beam or a beam provided by an optical parametric oscillator.