:: What is ASE?
ASE stands for Amplified Spontaneous Emission. Let’s explain it in two steps.
1. Spontaneous Emission
Spontaneous emission is the process by which an atom, molecule or nucleus in an excited state drops to a lower-energy state, resulting in the creation of a photon.
2. How is Spontaneous Emission Amplified
If the spontaneous emission happens in a gain medium, such as EDFA (Erbium Doped Fiber Amplifier), this spontaneous emission can be amplified by the process of stimulated emission as described below.
Stimulated emission is the process by which, when perturbed by a photon, matter may lose energy resulting in the creation of another photon. The perturbing photon is not destroyed in the process, and the second photon is created with the same phase, frequency, polarization, and direction of the travel as the original.
ASE is produced when a laser gain medium is pumped to produce a population inversion. Feedback of the ASE by the laser’s optical cavity may produce laser operation if the lasing threshold is reached.
Thus, first, spontaneous emission happens, then this spontaneous emission is amplified by the stimulated emission process in the gain medium (since there are more atoms being pumped into the excited state).
:: What is ASE Light Source
People utilized this ASE process to make broadband ASE light source which is essential for many different telecommunications, fiber sensing, fiber optic gyroscope, and test & measurement applications.
Since spontaneous emission process can produce photons in a wide wavelength range, such as the C band, C+L band, etc. When amplified by the gain medium, the output is a broadband, high power laser light source.
This figure shows the optical spectrum of 1550nm ASE light source.
:: ASE Light Source Product Vendors:
By no means complete, here are some ASE light source product vendors, just for your reference.