Comparative studies of eye-safe intracavity and extracavity optical parametric oscillators with an unstable telescopic cavity
Comparative studies of eye-safe intracavity and extracavity optical parametric oscillators with an unstable telescopic cavity
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DOI：
10.1007/s10812-006-0126-9
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发表时间：
2006-07
影响因子：
0.7
通讯作者：
V. Dashkevich;A. I. Vodchits;V. Orlovich;N. Kazak;V. Pavlenko;V. I. Pokryshkin;I. P. Petrovich;V. V. Rukhovets-V.
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作者：
V. Dashkevich;A. I. Vodchits;V. Orlovich;N. Kazak;V. Pavlenko;V. I. Pokryshkin;I. P. Petrovich;V. V. Rukhovets-V.
实验研究了具有不稳定伸缩腔的人眼安全光学参量振荡器(OPO)在脉冲近单模KGW：ND泵浦激光器的平面平行腔内(腔内OPO)和腔外(腔外OPO)放置时的激光特性。我们使用KTP晶体作为光学参量振荡器的非线性介质。结果表明，内腔型OPO具有较高的激光效率。我们观察到，腔内OPO引入的非线性损耗在腔截面上的不均匀分布导致了来自泵浦激光器的辐射束的直径和发散率的增加，以及其时间激光动力学与横向光束坐标的关系。我们提出了一个物理模型，定性地解释了具有内腔OPO的辐射源的时空激光动力学。这两个OPO版本产生的辐射束具有大致相同的发散。在电泵浦能量为7.3J、腔长为77 cm的KGW：ND激光器中，腔内OPO和腔外OPO分别产生能量为14.5mJ和12.0mJ、脉宽分别为18纳秒和13纳秒的脉冲。当输出光束直径为2 mm时，86.5%的人眼安全辐射(λ=1.578µm)发散角不大于5.5mrad。
We have experimentally studied the lasing characteristics of an eye-safe optical parametric oscillator (OPO) with an unstable telescopic cavity when it is placed inside (intracavity OPO) and outside (extracavity OPO) the plane-parallel cavity of a pulsed, nearly single-mode KGW:Nd pump laser. We used a KTP crystal as the nonlinear medium for the OPO. We have shown that the intracavity OPO has the higher lasing efficiency. We have observed that the distribution of nonlinear losses introduced by the intracavity OPO, nonuniform over the cavity cross section, leads to an increase in the diameter and divergence of the radiation beam from the pump laser and a dependence of its temporal lasing dynamics on the transverse beam coordinate. We propose a physical model qualitatively explaining the spatial and temporal lasing dynamics of a radiation source with an intracavity OPO. Both OPO versions generate beams of radiation with about the same divergence. When the KGW:Nd laser has an electrical pumping energy of 7.3 J and a cavity length of 77 cm, the intracavity OPO and the extracavity OPO emit pulses with energies of 14.5 mJ and 12.0 mJ and duration 18 nsec and 13 nsec respectively. The divergence of the eye-safe radiation (λ = 1.578 µm) at 86.5% of the total pulse energy is no greater than 5.5 mrad for an OPO output beam diameter of = 2 mm.