Tunable fiber laser concepts in the 2µm spectral range for tunable dual wavelength emission
Tunable fiber laser concepts in the 2µm spectral range for tunable dual wavelength emission
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2μm 光谱范围内的可调谐光纤激光器概念，用于可调谐双波长发射
DOI：
10.1117/12.2559948
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发表时间：
2020
期刊：
影响因子：
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通讯作者：
M. Jäger
中科院分区：
文献类型：
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作者：
T. Tiess;A. Hartung;M. Becker;M. Rothhardt;R. Dauliat;B. Leconte;G. Humbert;P. Roy;M. Jäger
光纤激光器是可调谐激光器的重要来源，这是由于稀土在玻璃基体中的转变（与晶体相比）具有宽而相对平坦的增益光谱。特别是铥（Tm）掺杂光纤，在双增益模块配置下，在2μm波长区域提供了高达330 nm的极宽可调性。最近，出现了新的概念，可以同步发射两种甚至更多波长。这些源对于通过四波混频（FWM）或差频产生（DFG）进行非线性频率转换特别有用。我们将提出一种非常通用的光纤集成方法，该方法基于在theta形腔中实现的光纤布拉格光栅（FBG）阵列。掺铥光纤源的典型平均功率为0.5W，在1931nm ~ 2040nm范围内可调。发射线宽度遵循光纤光栅的光谱特性，在我们的情况下通常为30GHz。这个概念允许一个恒定的波长无关的重复率，以及同步发射两个甚至三个独立的可调波长。通过光门控进行纯电子调谐，此外脉冲持续时间可以在4ns和25ns之间调谐。开关速度非常快，测量结果小于10μs。这些实验将与基于VLMA光纤的不同方法进行对比，该方法与一组两个体积布拉格光栅（VBG）相关联，其中一个是角度可调的。这个概念允许脉冲（调q）和连续波操作，并具有连续和更宽的可调性，特别是高达144nm，也是双波长模式。在连续模式下输出功率为>.5 w，在调q模式下脉冲峰值功率为12kW，脉冲持续时间为25ns。
Fiber lasers are a great source for tunable lasers due to the wide and relatively flat gain spectra of rare earth transitions in a glassy host (as compared to crystals). Thulium (Tm)-doped fibers, in particular, offer an extremely wide tunability of up to 330 nm in the 2μm wavelength region in a dual gain module configuration1. More recently, new concepts have emerged, which allow the synchronized emission of two or even more wavelengths2. These sources are particularly useful for nonlinear frequency conversion via four-wave mixing (FWM) or difference frequency generation (DFG). We will present a very versatile fiber-integrated approach based on Fiber-Bragg-Grating (FBG) arrays implemented in a theta-shaped cavity. The Tm-doped fiber source emits typical average powers of 0.5W and is tunable from 1931nm to 2040nm. The emission linewidth follows the spectral characteristic of the FBG and is typically 30GHz in our case. This concept allows a constant wavelength-independent repetition rate as well as a synchronous emission of two or even three independently tunable wavelengths. The tuning is performed purely electronically by optical gating, and in addition the pulse duration can be tuned between 4ns and 25ns. The switching speed is very fast and was measured to be less than 10μs. These experiments will be contrasted with a different approach based on a VLMA fiber associated to a set of two volume Bragg gratings (VBG), one of them being angle-tunable. This concept allows pulsed (Q-switched) as well as CW operation and features a continuous and wider tunability of up to 144nm especially and also the dual wavelength mode. The output power was > 4.5W in CW mode and pulse peak power of 12kW have been obtained in the Q-switched mode with pulse durations of 25ns.