The first results of the liquid nitrogen cooling effect on the spectral properties of a phosphor-related bismuth active center (BAC-P) have been presented. It is found that the small-signal absorption bands of BACs are mildly affected at liquid nitrogen temperature (LNT, 77 K), while the unsaturable absorption level is lowered moderately. Meanwhile, noticeable shape changes of luminescence spectra and enhanced luminescence intensity (∼ twice) of BAC bands were revealed at LNT upon excitation at 830 or 980 nm, which is contributed by the notable growth of BAC-P. In addition, the influence of cooling on the on-off gain performance of BACs is also explored. Furthermore, the laser-induced effect on the luminescence of BAC-P upon cooling at LNT is also investigated, revealing a noticeable increase (∼10%) instead of photobleaching. These experimental results bring new insights into the temperature-related spectral properties of BACs and provide an effective way for tuning the luminescence scheme for Bi-doped fibers by cryogenics for the desired spectral range 1.26-1.36 μm.

中文翻译：

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液氮冷却对掺铋磷硅酸盐光纤中BAC-P在液氮温度下光谱性能的影响

液氮冷却效应对磷相关铋活性中心 (BAC-P) 的光谱特性的初步结果已经呈现。结果表明，液氮温度（LNT，77 K）下，BACs的小信号吸收带受到轻微影响，不饱和吸收水平适度降低。同时，在 830 或 980 nm 激发后，LNT 显示发光光谱的显着形状变化和 BAC 带的增强发光强度（~两倍），这是由于 BAC-P 的显着增长。此外，还探讨了冷却对 BAC 开关增益性能的影响。此外，还研究了激光对 LNT 冷却时 BAC-P 发光的影响，发现显着增加（~10%）而不是光漂白。