Most light sources are [[Coherence|incoherent]]. For example, ordinary light bulbs emit photons of light over a wide range of frequencies and with random phases. [[Laser|Lasers]], on the other hand, differ from other light sources in that they emit coherent light. Their coherence is what makes lasers so appealing for many technological and scientific applications. Lasers can emit light that is coherent in two distinct ways: *spatially* and *temporally* coherent. High spatial coherence allows lasers to be focused on a tight spot, which is crucial for laser cutting, lithography and other applications. Temporal coherence allows lasers to emit light with a narrow frequency [[Spectrum|spectrum]]. >[!read]- Further Reading >[!ref]- References