Adamu Abubakar I, Habib Md Selim, Smith Callum R, Antonio Lopez J Enrique, Uhd Jepsen Peter, Amezcua-Correa Rodrigo, Bang Ole, Markos Christos
DTU Fotonik, Technical University of Denmark, Kgs. Lyngby, DK-2800, Denmark.
CREOL, The College of Optics and Photonics, University of Central Florida, Orlando, FL-32816, USA.
Sci Rep. 2020 Mar 18;10(1):4912. doi: 10.1038/s41598-020-61847-w.
Deep-UV (DUV) supercontinuum (SC) sources based on gas-filled hollow-core fibers constitute perhaps the most viable solution towards ultrafast, compact, and tunable lasers in the UV spectral region, which can even also extend into the mid-infrared (IR). Noise and spectral stability of such broadband sources are key parameters that define their true potential and suitability towards real-world applications. In order to investigate the spectral stability and noise levels in these fiber-based DUV sources, we generate an SC spectrum that extends from 180 nm (through phase-matched dispersive waves - DWs) to 4 μm by pumping an argon-filled hollow-core anti-resonant fiber at a mid-IR wavelength of 2.45 μm. We characterize the long-term stability of the source over several days and the pulse-to-pulse relative intensity noise (RIN) of the DW at 275 nm. The results indicate no sign of spectral degradation over 110 hours, but the RIN of the DW pulses at 275 nm is found to be as high as 33.3%. Numerical simulations were carried out to investigate the spectral distribution of the RIN and the results confirm the experimental measurements and that the poor noise performance is due to the high RIN of the mid-IR pump laser, which was hitherto not considered in numerical modelling of these sources. The results presented herein provide an important step towards an understanding of the noise mechanism underlying such complex light-gas nonlinear interactions and demonstrate the need for pump laser stabilization.
基于充气空心光纤的深紫外（DUV）超连续谱（SC）源或许是在紫外光谱区域实现超快、紧凑且可调谐激光器的最可行解决方案，其甚至还能延伸至中红外（IR）。此类宽带光源的噪声和光谱稳定性是决定其真正潜力以及适用于实际应用的关键参数。为了研究这些基于光纤的深紫外光源中的光谱稳定性和噪声水平，我们通过在2.45μm的中红外波长泵浦充氩空心反谐振光纤，产生了一个从180nm（通过相位匹配色散波——DWs）延伸至4μm的超连续谱。我们表征了该光源在数天内的长期稳定性以及275nm处DW的逐脉冲相对强度噪声（RIN）。结果表明在110小时内没有光谱退化的迹象，但发现275nm处DW脉冲的RIN高达33.3%。进行了数值模拟以研究RIN的光谱分布，结果证实了实验测量结果，并且表明较差的噪声性能是由于中红外泵浦激光器的高RIN，而这在这些光源的数值建模中迄今未被考虑。本文所呈现的结果朝着理解此类复杂的光 - 气非线性相互作用背后的噪声机制迈出了重要一步，并证明了对泵浦激光器进行稳定化的必要性。
