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Pulse Pickers

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Definition: electrically controlled optical switches used for extracting single pulses from a pulse train

German: Pulsauswähler

Categories: photonic devices, light pulses

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Ultrashort pulses are in most cases generated by a mode-locked laser in the form of a pulse train with a pulse repetition rate of the order of 10 MHz – 10 GHz. For various reasons (see below), it is often necessary to pick certain pulses from such a pulse train, i.e., to transmit only certain pulses and block all the others. This can be done with a pulse picker, which is essentially an electrically controlled optical switch.

Types of Pulse Pickers

A pulse picker is in most cases either an electro-optic modulator or an acousto-optic modulator, combined with a suitable electronic driver. In the case of an electro-optic device, a pulse picker consists of a Pockels cell and some polarizing optics, e.g. a thin-film polarizer; the Pockels cell manipulates the polarization state, and the polarizer then transmits or blocks the pulse depending on its polarization.

The principle of an acousto-optic pulse picker is to apply a short RF pulse to the acousto-optic modulator so as to deflect the wanted pulse into a slightly modified direction. The deflected pulses can then pass an aperture, whereas the others are blocked.

In any case, the required speed of the modulator is determined by the temporal distance of pulses in the pulse train (i.e. by the pulse repetition rate of the pulse source), rather than by the pulse duration.

The electronic driver of a pulse picker may fulfill additional functions. For example, it may use the signal from a fast photodiode, sensing the original pulse train, in order to synchronize the switching with the input pulses. A trigger signal may then come at any time, and the electronics will act on the switch at the proper time to transmit the next arriving input pulse.

Applications of Pulse Pickers

Some typical applications of a pulse picker are described in the following:

Important Properties of Pulse Pickers

Depending on the application, different properties of a pulse picker can be critical:

See also: electro-optic modulators, acousto-optic modulators, pulse generation, pulse repetition rate, regenerative amplifiers, ultrashort pulses
and other articles in the categories photonic devices, light pulses

In the RP Photonics Buyer's Guide, 17 suppliers for pulse pickers are listed.

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