Picosecond Pulsed-Periodic High-Peak Power Nd:YAG Laser Operationally Controlled by KTP-Based Pockels Cell

Vyacheslav Morozov,Andrey Olenin,Dmitry Yakovlev,Vladimir Rusov,Alexander Gorchakov,Vladimir Tunkin,Sergei Doroganov

doi:10.3390/cryst12030368

Vyacheslav Morozov, Andrey Olenin + Show 5 more

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https://doi.org/10.3390/cryst12030368

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Abstract

Electro-optical modulators are effectively used for ultrafast pulse lasers operation control. The scheme of picosecond pulse-periodic high-peak-power Nd:YAG lasers is composed of an active-passive mode-locked and negative feedback-controlled master oscillator and regenerative amplifier based on common end-diode-pumped Nd:YAG crystal. A double-crystal thermally compensated Pockels cell based on KTP crystals of the Y-cut direction is employed as a key control element. The cell was assembled using a pair of equal-length crystals grown according to high-resistivity technology. The scheme provides output pulses with energy up to 1.6 mJ, a duration of 25 ps at repetition rates tunable from 0 to 200 Hz. The laser operation stages are analyzed in detail. The scheme looks attractive and promising for developing advanced ultrafast laser systems with higher repetition rates, peak and, accordingly, average power levels. The Pockels cell based on KTP crystals expands the line of available fast electro-optical control elements, along with the previously used RTP ones. The factors limiting laser pulse energy and repetition rate are discussed. Parasitic nonlinear conversion in the crystals of the Pockels cell along the axis may play an essential role. The results of comparative measurements of the second and third harmonics made with the Pockels cells based on KTP and RTP crystals of both X-cut and Y-cut directions are presented. The minimum second and third harmonics efficiency levels observed in the Y-cut Pockels cells of the KTP crystal seem to be their important advantage.

Highlights

We demonstrate the scheme and operation details of a highpeak-power picosecond Nd:YAG laser built on the basis of a master oscillator/regenerative amplifier approach
Double-crystal, thermally compensated Pockels cell based on KTP crystals of Y-cut direction is used as a key element for the implementation of a picosecond pulse-periodic high-peak-power Nd:YAG laser scheme with electro-optical operation control
The laser scheme uses an active-passive mode-locked and negative feedbackcontrolled master oscillator and regenerative amplifier based on a common end-diodeqcw-pumped Nd:YAG crystal

Summary

Introduction

The scheme of picosecond pulse-periodic high-peak-power Nd:YAG lasers is composed of an activepassive mode-locked and negative feedback-controlled master oscillator and regenerative amplifier based on common end-diode-pumped Nd:YAG crystal. Pockels cell based on KTP crystals of the Y-cut direction is employed as a key control element. The Pockels cell based on KTP crystals expands the line of available fast electro-optical control elements, along with the previously used RTP ones. The results of comparative measurements of the second and third harmonics made with the Pockels cells based on KTP and RTP crystals of both X-cut and Y-cut directions are presented. The minimum second and third harmonics efficiency levels observed in the Y-cut Pockels cells of the KTP crystal seem to be their important advantage. High-peak-power picosecond lasers have been used in a variety of scientific and technological applications, such as time-resolved nonlinear laser spectroscopy [1–3], laser ablation and micromachining [4,5], picosecond optical parametric amplifiers pumping [6], photo-guns equipped in electron accelerator injectors [7,8], precise satellite [9,10] and lunar [11,12] laser ranging, laser driving wide-band high-power semiconductor switches [13,14], coherent anti-Stokes Raman microscopy [15], two-photon bioimaging [16], aesthetic cosmetology and dermatology [17,18] and clinical surgery [19,20]

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