inhomogeneous saturation (original) (raw)

Author: the photonics expert (RP)

Definition: gain saturation effects which alter the shape of the gain spectrum

Category: article belongs to category physical foundations physical foundations

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DOI: 10.61835/014 Cite the article: BibTex BibLaTex plain text HTML Link to this page! LinkedIn

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What is Inhomogeneous Saturation?

When a gain medium amplifies a strong laser beam, the laser gain is saturated, i.e. reduced to some extent (→ gain saturation). Under certain circumstances, the saturation can be inhomogeneous, i.e. it can be stronger around the wavelength of the laser beam than at other wavelengths, as illustrated in Figure 1.

inhomogeneous gain saturation

Figure 1: An illustration of inhomogeneous gain saturation.

A laser at 1064 nm saturates the gain around 1064 nm more than the gain at other wavelengths. For comparison, the unsaturated gain (without laser power) is shown as a dotted curve.

Inhomogeneous saturation characteristics are related to inhomogeneous broadening and can arise when different laser ions in the gain medium can occupy different lattice sites (assuming a solid-state medium). This is particularly the case in glasses. However, some glasses exhibit nearly homogeneous gain saturation despite the great variety of lattice sites. This is the case for neodymium-doped phosphate glasses, for example, whereas silicate glasses show strongly inhomogeneous saturation.

Spatial hole burning in linear laser resonators can also lead to inhomogeneous saturation. In that case, laser ions at different locations in the gain medium “see” different wavelengths with different intensities because the period of the standing-wave pattern depends on the wavelength.

In a laser, inhomogeneous saturation characteristics can influence the optical spectrum of the laser output and restrict the wavelength tuning range. For a mode-locked laser, this effect can make it easier to obtain short pulses, but can also adversely affect the self-starting characteristics.

Frequently Asked Questions

This FAQ section was generated with AI based on the article content and has been reviewed by the article’s author (RP).

What is inhomogeneous saturation?

Inhomogeneous saturation is a type of gain saturation where the amplification gain is reduced more strongly around the wavelength of an intense laser beam than at other wavelengths.

What causes inhomogeneous saturation in laser gain media?

It is related to inhomogeneous broadening and typically occurs when laser ions in a solid-state medium occupy a variety of different local environments (lattice sites), which is particularly the case in glasses.

How can spatial hole burning lead to inhomogeneous saturation?

In a linear laser resonator, spatial hole burning causes inhomogeneous saturation because the standing-wave intensity patterns depend on the wavelength. Therefore, laser ions at different locations are saturated to different degrees for different wavelengths.

What are the effects of inhomogeneous saturation in a laser?

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