Abstract: An optical device for amplifying or emitting an optical beam of given wavelength comprises an optical source (20) in combination with a primary optical device (10) which is a semiconductor optical amplifier (SOA), a gain-clamped semiconductor optical amplifier (GCSOA), a sub-threshold gain-clamped semiconductor optical amplifier (SGCSOA), a laser diode (LD) or a superluminescent LED (SLED). The primary optical device (10) delivers an output signal of given wavelength called the signal beam and optionally receives an input beam at the same wavelength as the signal beam. Operation of the primary optical device (10) is assisted by a holding beam supplied by the optical source (20). The holding beam is of smaller wavelength than the signal beam, the holding beam wavelength being tuned close to the transparency wavelength of the primary optical device to provide a holding beam at transparency (HBAT) mode.