Thermal management of fiber-coupled-diode pumped Tm:YLF laser crystal slab

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Tezin Türü: Yüksek Lisans

Tezin Yürütüldüğü Kurum: Orta Doğu Teknik Üniversitesi, Mühendislik Fakültesi, Makina Mühendisliği Bölümü, Türkiye

Tezin Onay Tarihi: 2014

Öğrenci: MERT BALTACIOĞLU

Danışman: HANİFE TUBA OKUTUCU ÖZYURT

Özet:

In end-pumped solid-state lasers, thermal effects in the lasing medium are important factors in determining the limits of the maximum achievable power and the laser beam quality. In the present study, thermal effects such as the maximum and average temperatures, thermal lens radius and thermally induced stress on a fiber-coupled-diode pumped Thulium(Tm)-doped-YLiF_4 (YLF) laser crystal slab with unity aspect ratio are investigated for different cooling geometries. The thermal effects are simulated and compared for the laser crystal slab pumped by Gaussian and top-hat incident pump profiles with one side surface, two parallel opposite side surfaces and all four side surfaces being used as the heat dissipating surfaces. The case with four heat dissipating side surfaces yielded significantly better results in terms of thermo-optical effects compared to those of the other two cooling cases. Also the top-hat pump profile outperformed the Gaussian profile in all cooling conditions. The introduction of crystal holders with different thermal conductivities on the steady-state thermal and thermo-optical performance of the slab is also investigated for all cooling cases. It is observed that the crystal holder acts as a constant steady-state conductive thermal resistance throughout the length of the crystal. Simulations favored the asymmetrically cooled 4-side cooling method. Accordingly, setups using two-stage holders are designed and experimented. The experimental data is found to be in agreement with the simulations. .