Encyclopedia … combined with a great Buyer's Guide!

Sponsors:     and others

Pump–probe Measurements

Definition: techniques for investigating ultrafast phenomena, where a pump pulse excites a sample and a probe pulse is used for probing the sample after an adjustable delay time

German: Pump-Probe-Messungen

Categories: optical metrology, methods

How to cite the article; suggest additional literature


URL: https://www.rp-photonics.com/pump_probe_measurements.html

Pump–probe measurements can be used to obtain information on ultrafast phenomena, typically on picosecond or femtosecond time scales. The general principle is the following:

  • The investigated object is hit by some pump pulse, which generates some kind of excitation (or other modification) in the sample.
  • After an adjustable time delay, a typically weaker probe pulse hits the sample, and its transmittance or reflectance is measured. That reveals to which extent the sample is still affected by the pump pulse at that time.
  • By monitoring the probe signal as a function of the time delay, it is possible to obtain information on the decay of the generated excitation, or on other processes initiated by the pump pulses.

The pump and probe pulses are in most cases derived from a common source, e.g. from a mode-locked laser and a beam splitter. The relative timing is controlled with an optical delay line. Note that a fast photodetector is not required; the temporal resolution is fundamentally limited only by the pulse duration of pump and probe pulses.

In some cases, the wavelengths of pump and probe beam are not identical. A so-called two-color pump–probe measurement, based on two synchronized sources of short pulses (e.g. a laser and an optical parametric oscillator, or two parametric oscillators pumped with the same laser) has additional capabilities in ultrafast laser spectroscopy. One may then perform pump–probe measurements with different pump and signal wavelengths. It is vital in such cases to ensure tight synchronization of the different laser sources with a very low relative timing jitter, as the jitter could otherwise spoil the attainable temporal resolution.

The probe signal is often quite weak. It may be averaged over many pulses in order to obtain a better signal-to-noise ratio, assuming that the behavior of the tested object is fully reproducible. That is often the case if the applied pulse intensities are not too high.

Examples for Applications of Pump–Probe Measurements

Characterization of Saturable Absorbers

Pump–probe measurements can be used, for example, to monitor the recovery of a saturable absorber (e.g. a SESAM) after its excitation. For SESAMs, one often observes a rather fast partial recovery, followed by a slower complete recovery of the saturable loss (see Figure 1).

reflectivity change in a SESAM, caused by a short pulse
Figure 1: Reflectance change of a semiconductor saturable absorber, hit by a short pulse at t = 0.


The speed of a photodiode can depend on various factors, one of them being the diffusion of photoexcited carriers. For investigating that, one may also very the exact position where the probe pulses are applied.

Laser Material Processing

In laser material processing, e.g. involving laser ablation, the occurring processes may be rather complicated. To some extent, they can be investigated with pump–probe measurements. For example, one may find out during which time interval after an intense pulse the material is found in liquid form.

Time-resolved Spectroscopy

Pump–probe methods are also used in various methods of time-resolved spectroscopy. Obviously, the addition of the temporal dimension to the spectral one greatly expands the opportunities for investigating systems.


The RP Photonics Buyer's Guide contains 9 suppliers for pump--probe measurement equipment. Among them:

Questions and Comments from Users

Here you can submit questions and comments. As far as they get accepted by the author, they will appear above this paragraph together with the author’s answer. The author will decide on acceptance based on certain criteria. Essentially, the issue must be of sufficiently broad interest.

Please do not enter personal data here; we would otherwise delete it soon. (See also our privacy declaration.) If you wish to receive personal feedback or consultancy from the author, please contact him e.g. via e-mail.

Your question or comment:

Spam check:

  (Please enter the sum of thirteen and three in the form of digits!)

By submitting the information, you give your consent to the potential publication of your inputs on our website according to our rules. (If you later retract your consent, we will delete those inputs.) As your inputs are first reviewed by the author, they may be published with some delay.

See also: time-resolved spectroscopy, ultrafast optics, saturable absorbers, semiconductor saturable absorber mirrors, optical sampling, synchronization of lasers, laser spectroscopy
and other articles in the categories optical metrology, methods


If you like this page, please share the link with your friends and colleagues, e.g. via social media:

These sharing buttons are implemented in a privacy-friendly way!