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Pump Depletion

Author: the photonics expert Dr. Rüdiger Paschotta (RP)

Definition: reduction in the transmitted pump power in a laser or nonlinear conversion device

Categories: article belongs to category nonlinear optics nonlinear optics, article belongs to category laser devices and laser physics laser devices and laser physics

Page views in 12 months: 569

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

Pump depletion is the phenomenon that the pump power for some process occurring in a device can be depleted e.g. due to conversion of the pump power into some other optical power. The term is most frequently used in the context of devices for nonlinear frequency conversion, such as frequency doubling, sum and difference frequency generation, and for optical parametric oscillators.

For example, a pump depletion of 60% in an optical parametric oscillator means that 60% of the injected pump power is converted into signal and idler power, assuming that losses through other processes are negligible. A strong pump depletion is the inevitable consequence of efficient power conversion, and the measurement of pump depletion can be useful for assessing and understanding the performance of nonlinear frequency conversion devices.

The degree of pump depletion (and thus efficiency) in some cases (e.g. for single-pass frequency doublers) rises monotonically with increasing pump power, whereas in other cases (often in OPOs, or in resonant frequency doublers) it is highest for a certain pump power. The maximum pump depletion can be limited by many effects, such as by mode matching and impedance matching of optical resonators, or transverse effects (e.g. back-conversion on the beam axis).

One may also consider pump depletion inside a nonlinear crystal. While this is hard to measure, it can be obtained from numerical simulations. In a high-gain OPA, for example, it may be weak initially and then become strong towards the output end.

More to Learn

Nonlinear frequency conversion

Optical parametric oscillators

Frequency doubling

Sum and difference frequency generation

Questions and Comments from Users

2022-11-13

How to know whether the pump is depleted in a simple SHG process using QPM?

The author's answer:

It is necessarily depleted once the conversion efficiency becomes significant.

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