The invention relates to sources of sub-picosecond optical pulses based on single-pass or double-pass optical amplifiers with an optical gain bandwidth in the 2-20 nm range. A passive pulse shaping filter is provided in front of the optical amplifier for pre-shaping seed optical pulses so as to passively pre-compensate for the gain narrowing effect in the optical amplifier. The passive pulse shaping filter may be based on a reflective thin film filter, which may be coupled to a mirror in a multi-pass configuration.

An optical amplification device includes: a semiconductor optical amplifier; a first detector that detects an input optical power of the semiconductor optical amplifier; a second detector that detects an output optical power of the semiconductor optical amplifier; and a controller that controls a driving current of the semiconductor optical amplifier, wherein the controller supplies a predetermined driving current to the semiconductor optical amplifier when an optical signal is not input to the semiconductor optical amplifier, the second detector detects an optical power of Amplified Spontaneous Emission (ASE) output from the semiconductor optical amplifier when the predetermined driving current is supplied to the semiconductor optical amplifier, and the controller controls the driving current of the semiconductor optical amplifier based on the input optical power of the semiconductor optical amplifier detected by the first detector, and the optical power of the ASE.

An optical semiconductor device includes an active layer having a plurality of quantum dot layers. The plurality of quantum dot layers include: a first quantum dot layer doped with a p-type impurity; and a second quantum dot layer doped with an n-type impurity and having an emission wavelength different from that of the first quantum dot layer.