What is the Difference Between Diffraction Grating and Transmission Grating

The key difference between diffraction grating and transmission grating is that diffraction gratings can separate polychromatic light into its constituent wavelengths, whereas transmission gratings are a type of diffraction gratings that involves diffraction of light in different angles to give a diffraction pattern.

There are four major types of diffraction gratings. These include ruled gratings, holographic gratings, transmission gratings, and reflection gratings. Therefore, transmission gratings are a type of diffraction gratings.

CONTENTS

1. Overview and Key Difference
2. What is Diffraction Grating  
3. What is Transmission Grating 
4. Diffraction Grating vs Transmission Grating in Tabular Form
5. Summary – Diffraction Grating vs Transmission Grating

What is Diffraction Grating?

A diffraction grating is an optical component having a periodic structure that can diffract light into several beams that tends to travel in different directions. These different directions are associated with different diffraction angles. This grating system can result in a color in the form of a structure coloration. Diffraction angles depend mainly on the wave incident angle, space between adjacent diffracting elements on the grating system, and wavelength of the incident light.

The grating system can act as a dispersive element. Therefore, we can use it as a monochromator and as a spectrometer. However, there are some other possible applications as well, which include optical encoders for high precision motion control and wave-front measurement.

In typical applications, a reflective grating contains ridges or rulings on the surface. However, a transmissive grating contains transmissive or hollow slits on the surface. This type of grating system can modulate the amplitude of an incident wave to create the relevant diffraction pattern. Also, there are gratings that can modulate the phases of incident waves compared to the amplitude. Moreover, we can produce these gratings using holography.

Usually, a diffraction grating forms rainbow colors upon illuminating a wide spectrum of a light source. For example, rainbow-like colors appearing on CDs and DVDs. Usually, a diffraction grating has parallel lines. But in a CD, there are spiral lines that are finely spaced between data tracks.

What is Transmission Grating?

Transmission gratings are a type of diffraction gratings that can be used in transmission. We can discuss transmission gratings in opposition to reflection grating systems. Reflection gratings reflect all incident light rather than absorbing or scattering the light. However, transmission gratings can diffract light at different angles.

A transmission grating system requires parallel slits on the grating surface. These are named transmissive or hollow slits. This type of grating can modulate the amplitude of an incident wave on the surface to create a diffraction pattern. Usually, the two major types of diffraction gratings are reflective gratings and transmissive gratings.

What is the Difference Between Diffraction Grating and Transmission Grating?

Transmission grating is a type of diffraction grating. The key difference between diffraction grating and transmission grating is that diffraction gratings can separate polychromatic light into its constituent wavelengths, whereas transmission gratings are a type of diffraction gratings that involves diffraction of light in different angles to give a diffraction pattern.

The below infographic presents the differences between diffraction grating and transmission grating in tabular form for side by side comparison.

Summary – Diffraction Grating vs Transmission Grating

A diffraction grating is an optical component having a periodic structure that can diffract light into several beams that tends to travel in different directions. Meanwhile, transmission gratings are a type of diffraction gratings that can be used in transmission. The key difference between diffraction grating and transmission grating is that diffraction gratings can separate polychromatic light into its constituent wavelengths, whereas transmission gratings are a type of diffraction gratings that involves diffraction of light in different angles to give a diffraction pattern.

Reference:

1. “Diffraction Grating.” Hyperphysics. Phy-Astr.Gsu.Edu, 2022.

Image Courtesy:

1. “An incandescent light-bulb viewed through a transmissive diffraction grating” By © Robert D. Anderson – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Phase Grating Transmission Small” By OlPr – Own work (CC0) via Commons Wikimedia