Laser light an example of quantum coherence?

[sci-guy]

There seems to be some debate as to whether laser light is an example of quantum coherence (as posted in this thread: link). I think it deserves its own discussion. I'm no expert in this field, so I mainly go by what I read; I found this interesting Wikipedia reference here:

In classical optics light is thought of as electromagnetic waves radiating from a source. Often, coherent laser light is thought of as light that is emitted by many such sources that are in phase. Actually, the picture of one photon being in-phase with another is not valid in quantum theory. Laser radiation is produced in a resonant cavity where the resonant frequency of the cavity is the same as the frequency associated with the atomic transitions providing energy flow into the field. As energy in the resonant mode builds up, the probability for stimulated emission, in that mode only, increases. That is a positive feedback loop in which the amplitude in the resonant mode increases exponentially until some non-linear effects limit it. As a counter-example, a light bulb radiates light into a continuum of modes, and there is nothing that selects anyone mode over the other. The emission process is highly random in space and time (see thermal light). In a laser, however, light is emitted into a resonant mode, and that mode is highly coherent. Thus, laser light is idealized as a coherent state.

Comments?

 

[eljose79]

I agree with the information provided in the Wikipedia reference regarding laser light and quantum coherence. In quantum theory, the concept of coherence refers to the ability of particles or waves to maintain a fixed phase relationship with each other. In the case of laser light, this coherence is achieved through the use of a resonant cavity where the frequency of the cavity matches the frequency of the atomic transitions responsible for emitting light. This allows for a positive feedback loop where the energy in the resonant mode increases exponentially, resulting in highly coherent laser light.

On the other hand, traditional light sources such as light bulbs emit light into a continuum of modes, resulting in a highly random emission process. This lack of coherence is what differentiates laser light from other forms of light.

Overall, I believe that laser light is a clear example of quantum coherence and its unique properties make it a valuable tool in various scientific and technological applications. However, as with any scientific concept, it is important to continue researching and discussing to gain a better understanding and potentially discover new insights.