Opt Lett. 2019 Apr 1;44(7):1817-1820. doi: 10.1364/OL.44.001817.
In the present Letter, a synthesized pseudothermal light source having high temporal coherence (TC) and low spatial coherence (SC) properties is used. The longitudinal coherence (LC) properties of the spatially extended monochromatic light source are systematically studied. The pseudothermal light source is generated from two different monochromatic laser sources: He-Ne (at 632 nm) and DPSS (at 532 nm). It was found that the LC length of such a light source becomes independent of the parent laser's TC length for a large source size. For the chosen lasers, the LC length becomes constant to about 30 μm for a laser source size of ≥3.3 mm. Thus, by appropriately choosing the source size, any monochromatic laser light source depending on the biological window can be utilized to obtain high axial resolution in an optical coherence tomography (OCT) system irrespective of its TC length. The axial resolution of 650 nm was obtained using a 1.2 numerical aperture objective lens at a 632 nm wavelength. These findings pave the path for widespread penetration of pseudothermal light into existing OCT systems with enhanced performance. A pseudothermal light source with high TC and low SC properties could be an attractive alternative light source for achieving high axial resolution without needing dispersion compensation as compared to a broadband light source.
在本信函中，使用了具有高时间相干性（TC）和低空间相干性（SC）特性的合成赝热光源。系统研究了空间扩展单色光源的纵向相干（LC）特性。该赝热光源由两个不同的单色激光源产生：氦氖（632nm）和 DPSS（532nm）。结果发现，对于较大的光源尺寸，这种光源的 LC 长度变得独立于母激光的 TC 长度。对于所选的激光，当激光源尺寸≥3.3mm 时，LC 长度变为约 30μm 左右保持恒定。因此，通过适当选择光源尺寸，可以利用任何依赖于生物窗口的单色激光光源在 OCT 系统中获得高轴向分辨率，而与 TC 长度无关。使用 632nm 波长的 1.2 数值孔径物镜获得了 650nm 的轴向分辨率。这些发现为将赝热光广泛引入具有增强性能的现有 OCT 系统铺平了道路。与宽带光源相比，具有高 TC 和低 SC 特性的赝热光源可以成为实现高轴向分辨率的有吸引力的替代光源，而无需进行色散补偿。
