What is Coherent Light

Horace He

Last Updated: August 7, 2023

What is Coherent Light

Coherent light is the electromagnetic radiation that exhibits synchronization in both the spatial and temporal domains. This synchronization is characterized by the waves shining in the same direction, swinging at the same level, and having the same phase. As a result, coherent light consists of a single-color light with a specific wavelength. The key characteristic of coherent light is its ability to maintain a fixed relationship between descriptive parameters such as frequency, polarization, and phase within a specific spatial and temporal context. This synchronization allows the waves to reinforce each other, resulting in a more focused and powerful light output.

Coherent light is commonly associated with laser technology, where it is generated through the process of stimulated emission using a semiconductor gain as a medium. It is also utilized in various applications that require precise timing, synchronization, and control of light propagation, such as in optical communication systems, holography, interferometry, and integrated photonics.

Frequently Asked Questions

What Is the Difference Between Coherent and Incoherent Light

Coherent light is characterized by having a single frequency and wavelength. On the other hand, incoherent light exhibits various light frequencies and its frequency can randomly change.

Are LED Lights Coherent

Unlike a laser, LED lights do not emit spectrally coherent or highly monochromatic light. However, their spectrum is narrow enough to be perceived by the human eye as a pure (saturated) color.

What Is the Benefit of Coherent Light

The benefit of coherent light is that it enables the implementation of multiplexing, which combines multiple signals into one. This feature facilitates a higher data rate and longer distance transmission. Additionally, coherent optics provides the flexibility to adjust the number of channels that can be multiplexed.

How Do You Make Light Coherent

We can generate coherent light from an incoherent source by discarding a significant portion of the light. This is achieved by initially filtering the light from the incoherent source to enhance its spatial coherence, followed by filtering it spectrally to improve its temporal coherence.

What Light Cannot Be Coherent

Two sources of light that are independent of each other cannot be coherent. This is due to the fact that light is emitted by individual atoms when they return to their ground state. Even the tiniest source of light consists of billions of atoms, making it impossible for them to emit light waves in the same phase.

Is White Light Coherent or Incoherent

Finally, white light, with its wide range of frequencies, is a wave that rapidly fluctuates in both amplitude and phase. Due to its short coherence time of only about 10 periods, it is commonly referred to as being incoherent.