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| VOLUME 123 (2026) | ISSUE 12 | PAGE 899 |
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Increasing the modulation instability threshold in a direct-diode-pumped Kerr-lens mode-locked Ti:Sa oscillator
K. E. Reznikov+*, A. O. Mavritskiy+, M. N. Esaulkov+, A. V. Naumov*×
+AVESTA Ltd., 108840 Troitsk, Moscow, Russia *P. N. Lebedev Physical Institute of the Russian Academy of Sciences, Troitsk Branch, 108840 Moscow, Russia ×Institute of Spectroscopy of the Russian Academy of Sciences (ISAN), 108840 Troitsk, Moscow, Russia
Abstract
At high pump powers and intracavity laser power of Kerr-lens mode-locked lasers, modulation instability inevitably arises, limiting pulse energy and duration; it has been studied for Diode Pumped Solid-State pumping but not for direct-diode pumping. We implement a direct-diode-pumped Ti:Sa oscillator using two GaN diodes at 455/465 nm. Varying the pump-lens focal length F suppresses modulation instability. For F=80 mm, we obtain stable 12 fs pulses (  100 nm bandwidth) with average power
up to 300 mW at 8 W of pump; further pump increase leads to noise and
breakup into sub-pulses. For F=60 mm, the spectrum broadens to 110-120 nm with
450 mW at 11 W. For F=50 mm, the spectrum is 127-140 nm
(10 fs pulse duration) and the power is 500 mW at 11 W, with MI absent.
This result provides a practical route to improving the efficiency and
stability of direct-diode-pumped Kerr-lens mode-locked Ti:Sa oscillators.
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