That's an expected behavior and well-known for laser beam, the reason is diffraction. See this article to get the idea about beam divergence over distance.AdrianMachin said:I wonder how a LASER could act like this?
AdrianMachin said:I have a red 650nm and <5mW LASER pointer, but the beam is not very coherent. Actually, when I point to a wall at an approximately 300 meters away, the red point gets very large (about a meter in diameter). I wonder how a LASER could act like this?
A LASER beam is considered coherent when all of its light waves have the same frequency and are in phase with each other. This means that the waves are all aligned and have a constant and predictable relationship with each other. When a LASER beam is not coherent, the light waves may have different frequencies and/or phases, resulting in a less predictable and less focused beam.
The coherence of a LASER beam is a crucial factor in determining its performance. A coherent beam is able to maintain its focus and intensity over long distances, making it useful for applications such as cutting, welding, and precision measurements. On the other hand, a non-coherent beam may spread out and lose intensity, limiting its effectiveness in these types of applications.
There are several factors that can cause a LASER beam to become non-coherent. These include vibrations or disturbances in the LASER system, temperature changes, and imperfections in the optical components. Additionally, external factors such as air turbulence or stray light can also affect the coherence of a LASER beam.
Yes, in most cases, a non-coherent LASER beam can be made coherent again. This can be achieved through techniques such as active stabilization of the LASER system, using high-quality optical components, and implementing proper shielding and isolation from external disturbances. However, in some cases, it may not be possible to fully restore coherence, and the LASER beam may need to be replaced.
While coherence is generally desirable in LASER beams, there are some applications where a non-coherent beam may be advantageous. For example, in some medical procedures, a non-coherent beam can be used to deliver a wider and more diffuse treatment, reducing the risk of damaging surrounding tissue. Additionally, non-coherent beams can be used in certain types of imaging techniques.