Fig. 3: Left: examples of light sources with different degrees of temporal and spatial coherence.
From: Low-coherence semiconductor light sources: devices and applications
Right: photon degeneracy of various light sources241. a Low-temporal coherence and high-spatial coherence light, which can be generated from SLDs, or from an LED passing through a pinhole. b High-temporal coherence and high-spatial coherence light, which is typically emitted from conventional single-mode lasers, such as single-mode vertical-cavity surface-emitting lasers (VCSELs) and distributed-feedback (DFB) lasers. c Low-temporal coherence and low-spatial coherence light, which is which is typically emitted from LEDs and conventional thermal light sources, like tungsten light bulbs and stars. d High-temporal coherence and low-spatial coherence light which can be generated by chaotic-cavity lasers, degenerate-cavity lasers, VCSEL arrays and random lasers.
