Highly stable subpicosecond neodymium (Nd3+) glass laser with passive mode locking and negative feedback

An electrically controlled feedback loop was used in a phosphate glass laser with passive mode locking to ensure stable generation of 500–600 fs pulses. This negative feedback loop ensured a high reproducibility of the energy and time characteristics of the pulses. The product of the spectral width of the pulses and their duration was 0.44.