Abstract
Pockels cells used as electro-optical modulators in high-power high-repetition lasers suffer from piezoelectric ringing phenomenon due to piezoelectric properties of the crystals. A new method for active suppression of the piezoelectric ringing in Pockels cells is proposed in this work. It is based on symmetric control of Pockels cell using burst of short positive and negative voltage pulses with the same amplitude instead of a single long pulse for light polarization modulation. Rising and falling edges of pulses of the burst induce symmetrical acoustic waves of the opposite phase and cancel the piezoelectric ringing of the crystal. A new high voltage driver capable of generating positive and negative pulses of tens of nanoseconds of 3 kV magnitude was developed for this purpose. The amplitude of laser beam intensity pulsations caused by the piezoelectric ringing can be reduced up to five times when active suppression method is used for the deuterated potassium dihydrogen phosphate (DKDP) Pockels cell. Such crystals like DKDP, LiNbO3, and LiTaO3 may benefit from the proposed method and find new use in lasers of high repetition rate where piezoelectric ringing is a major limiting factor.
Highlights
High power laser systems are increasingly used in material processing
Investigation results show that the proposed active piezoelectric ringing suppression method for DKDP Pockels cells can be implemented in the intracavity as well as extracavity applications of lasers
Implementing a burst of high voltage pulses which contains just three pulses of 0.33 μ s instead of continuous pulses can reduce the amplitude of the piezoelectric ringing in the active time window up to five times
Summary
High power laser systems are increasingly used in material processing. The so-called. Q-switching technique is used to produce high power laser pulses. Voltage pulses change the refractive index of the Pockels cell material and, as a consequence, induces changes in the polarization of the laser beam [10,11,12]. Optical contrast ratio is measured by placing a Pockels cell between crossed polarizers (Figure 1a). Beam intensity is measured using a detector that produces a signal (voltage Ud ) proportional to the light intensity and this signal we call optical response.
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