Can you, please, also specify what kind of laser exactly are you looking for? Pulse or CW? Single or multimode, etc. In general, most of commercially available high-power lasers (which, as known, are mostly used as a pump) are operating at a lower wavelength range. If you want to achieve such a high power as 600 mW at 1554 nm wavelength range, then you might need to consider either Erbium or Raman amplification laser schemes.