Abstract: A pulse modification apparatus includes at least one pulse stretcher for dispersive stretching of laser pulses and/or at least one pulse compressor for dispersive compression of the laser pulses, an actuator for setting a dispersion of the at least one pulse stretcher or a dispersion of the at least one pulse compressor by setting at least one manipulated variable, a controller for controlling the actuator based on a measurement signal, and an ambient sensor for detecting at least one ambient parameter as the measurement signal. The dispersion of the at least one pulse stretcher or the dispersion of the at least one pulse compressor is dependent on the at least one ambient parameter.