ASE is produced when a laser gain medium is pumped to produce a population inversion. This amplified luminescence may be used in applications where light with low temporal coherence but good spatial coherence is required.
The temporal coherence of ASE can be very low. In the time domain, the associated electric field exhibits fast random fluctuations, i.e., it has a rather short coherence time and coherence length. In the frequency domain, this corresponds to a large optical bandwidth. That bandwidth can be of the order of the gain bandwidth, but particularly in high-gain situations it is often substantially smaller than that.
The spatial coherence of ASE depends strongly on the circumstances. ASE from a short laser crystal, which is pumped with a large mode area, can have quite low spatial coherence, as the effective laser gain in substantially different propagation directions can be similar. On the other hand, ASE from a rare-earth-doped single-mode fiber can exhibit essentially perfect spatial coherence. This implies that such ASE can be well focused to a very small spot if suitable focusing optics (with low chromatic aberrations) are used.
SASE is an amplified spontaneous emission (ASE) source operation around 1550nm and single mode optical fibre output for test and measurement application. It is based on an erbium-Doped silicon and the optical output has a range 3-5mw and 10-15mw typical power. The optical emission is unpolarized and the broad spectral width, measured 20nm.
- Source of optical sensors based on broadband interferometer
- Optical coherence tomography