The ASE (Amplified Spontaneous Emission) light source is a type of broadband light source that emits light over a wide range of wavelengths, typically spanning from the visible to the near-infrared regions of the electromagnetic spectrum. ASE light sources are commonly used in a variety of applications in optics and photonics, including fiber optic sensing, optical coherence tomography, and spectroscopy.

ASE light sources work by amplifying the spontaneous emission of light from an optical gain medium, which is typically a fiber optic or a waveguide. The gain medium is optically pumped to create a population inversion, which causes the spontaneous emission of light to be amplified through stimulated emission. The resulting light is highly coherent and has a continuous spectrum, making it useful for a wide range of applications.

ASE light sources are often preferred over other broadband light sources, such as supercontinuum sources, because they offer higher power levels and better stability. However, they typically have a narrower spectral bandwidth than supercontinuum sources, which can limit their usefulness in certain applications that require a broad spectral range.