What is the Difference Between Temporal and Spatial Coherence?

🆚 Go to Comparative Table 🆚

The difference between temporal and spatial coherence lies in the correlation between waves at different points in time and space, respectively. Here is a summary of the differences:

  • Temporal Coherence: This refers to the correlation between waves observed at different moments in time. It is a measure of the time period for which light emitted from a source remains coherent. Temporal coherence is related to the interval during which the light source emits coherent light waves.
  • Spatial Coherence: This describes the correlation between waves at different points in space, either lateral or longitudinal. Spatial coherence is a measure of how well the waves maintain their phase relationship across a given area or volume.

Both temporal and spatial coherence are important in various applications, such as interferometry, holography, optical imaging systems, and remote sensing technologies.

Comparative Table: Temporal vs Spatial Coherence

The main difference between temporal and spatial coherence lies in their scopes: temporal coherence describes the correlation among waves observed at separate time instances, while spatial coherence describes the correlation between waves at distinct points in space, whether transverse or parallel in the same direction. Here is a table summarizing their differences:

Property Temporal Coherence Spatial Coherence
Definition Measures the phase correlation of a light wave at different locations along its path. Measures the phase correlation of a light wave at different points perpendicular to its path.
Description Correlation between waves observed at separate time instances. Correlation between waves at distinct points in space, either lateral or longitudinal.
Monochromaticity Used to characterize the degree of monochromaticity exhibited by a source. Helps explain how two points in space can have a wave-like behavior spreading out in one or two directions.
Coherence Length The distance a wave can travel during the time of Tc (a measure of the coherence time). Refers to the relationship between points on a wave across all moments in time.
Interference Explains how a wave can engage in self-interference during a specific period. Helps explain the phenomenon of interference fringes in the Young's interference experiment.

In summary, temporal coherence is concerned with the phase correlation of waves at different moments in time, while spatial coherence deals with the phase correlation of waves at distinct points in space.