Karim M R, Al Kayed Nayem, Rabiul Hossain Md, Rahman B M A
Appl Opt. 2020 Jul 10;59(20):5948-5956. doi: 10.1364/AO.395705.
Since the first observation by Alfano and Shapiro in the 1970s [Phys. Rev. Lett.24, 584 (1970)PRLTAO0031-900710.1103/PhysRevLett.24.584], supercontinuum generation study has become an attractive research area in the field of broadband light source design, including its use in various applications associated with nonlinear optics in recent years. In this work, the numerical demonstration of ultrabroadband supercontinuum generation in the mid-infrared (MIR) region via the use of complementary metal-oxide semiconductor compatible Si-rich silicon nitride as the core in a planar waveguide design employing one of two materials, either or glass, as the top and bottom claddings is explored. A rigorous numerical investigation of broadband source design in the MIR using 2 mm long Si-rich silicon nitride waveguides is carried out in terms of waveguide structural parameter variations, input peak power variation, varying unexpected deformation of the waveguide along the core region during fabrication, and spectral coherence analysis. Among the several waveguide models studied, two promising designs are identified for wideband supercontinuum generation up to the MIR using a relatively low input peak power of 50 W. Simulation results reveal that spectral coverage spanning from 0.8 µm to 4.6 µm can be obtained by using a -cladded waveguide, and similar spectral coverage is also predicted for the other design, a -cladded waveguide. To the best of our knowledge, this is the widest spectral span in the MIR region employing a Si-rich silicon nitride waveguide so far. In dispersion tuning as well as in supercontinuum generation, the effect of possible unexpected waveguide deformation along the transverse directions during fabrication is also studied. No significant amount of spectral change is observed in the proposed model for a maximum of 10° inside/outside variation along the width. On the other hand, even 1° upward/downward variation along the thickness could cause substantial spectral change at the waveguide output. Finally, the obtained output spectra from the proposed waveguides are found to be highly coherent and can be applied in various MIR region applications such as optical coherence tomography, spectroscopic measurement, and frequency metrology.
自20世纪70年代阿尔法诺和夏皮罗首次观测到以来[《物理评论快报》24, 584 (1970)PRLTAO0031 - 900710.1103/PhysRevLett.24.584]，超连续谱产生研究已成为宽带光源设计领域一个有吸引力的研究领域，包括近年来其在与非线性光学相关的各种应用中的使用。在这项工作中，探索了在平面波导设计中，通过使用互补金属氧化物半导体兼容的富硅氮化硅作为核心，以两种材料之一（或玻璃）作为顶部和底部包层，在中红外（MIR）区域产生超宽带超连续谱的数值演示。针对使用2毫米长的富硅氮化硅波导的MIR宽带光源设计，从波导结构参数变化、输入峰值功率变化、制造过程中沿核心区域波导意外的不同变形以及光谱相干分析等方面进行了严格的数值研究。在所研究的几种波导模型中，确定了两种有前景的设计，可使用相对较低的50瓦输入峰值功率在MIR范围内产生宽带超连续谱。模拟结果表明，使用包层波导可获得从0.8微米到4.6微米的光谱覆盖范围，另一种设计（包层波导）也预测有类似的光谱覆盖范围。据我们所知，这是迄今为止使用富硅氮化硅波导在MIR区域实现的最宽光谱跨度。在色散调谐以及超连续谱产生过程中，还研究了制造过程中沿横向方向波导可能出现的意外变形的影响。对于沿宽度方向最大10°的内外变化，在所提出的模型中未观察到显著的光谱变化。另一方面，沿厚度方向即使1°的上下变化也可能在波导输出端引起显著的光谱变化。最后，发现从所提出的波导获得的输出光谱具有高度相干性，可应用于各种MIR区域应用，如光学相干断层扫描、光谱测量和频率计量。
