Determination of the Residual Amplified Spontaneous Emission in Single-Mode Semiconductor Optical Amplifiers

The Master-Oscillator-Power-Amplifier (MOPA) is a laser light source best suited to provide high power, stable frequency, and narrow linewidth emission. In state-of-the-art MOPA systems, semiconductor optical amplifiers (SOAs) with single-mode lateral waveguides provide a compromise between the demands for high power on one side and excellent beam quality and small astigmatism of the optical mode on the other. The amplified spontaneous emission (ASE) in SOAs remains a limiting factor for the deployment of the MOPA systems in quantum technology applications. The presence of ASE reduces the carrier density and hence the device efficiency, increases the noise in the output signal, and adds incoherent background radiation that is critical, for example, for atom interferometry applications. It is therefore important to understand the dependence of the ASE on the design and operating conditions of an SOA in detail in order to develop SOAs optimized for applications that require spectrally very pure radiation.