Parylene C (PPXC) is a polymer deposited from the gas phase to form optically clear thin films used in devices including waveguides and sensors. The performance of these devices depends on the visible and near infrared absorption coefficient of PPXC. However, the absorption coefficient is difficult to measure. This is because PPXC films are typically too thin to exhibit detectable absorption in conventional transmittance measurements. To address this challenge, a method involving measuring the transmittance of multiple films immersed together in a liquid filled cuvette was devised. This increased the sensitivity to absorption by increasing the path length in PPXC, while also minimizing reflections and surface losses. Using 200-500 µm thick films, this method was applied to measure the absorption coefficient of PPXC at wavelengths in the range 330-3300 nm. The coefficient was found to vary spectrally by more than two orders of magnitude from 0.025 mm^-1 at 1562 nm to 7.7 mm^-1 at 3262 nm. These absorption measurements could aid the design of PPXC based sensors and waveguides. The method could be useful for measuring the absorption coefficient of other thin, low-loss materials, particularly those for which it is challenging to obtain thick samples such as other polymers deposited from the gas phase in a similar manner to PPXC.

中文翻译：

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聚对二甲苯 C 的可见光和近红外光吸收系数光谱通过在充满液体的比色皿中的薄膜透射光来测量

Parylene C (PPXC) 是一种从气相沉积的聚合物，可形成光学透明薄膜，用于包括波导和传感器在内的设备。这些器件的性能取决于 PPXC 的可见光和近红外吸收系数。然而，吸收系数难以测量。这是因为 PPXC 薄膜通常太薄而无法在传统的透射率测量中表现出可检测的吸收。为了应对这一挑战，设计了一种方法，该方法涉及测量一起浸入充满液体的比色皿中的多个薄膜的透射率。这通过增加 PPXC 中的路径长度增加了对吸收的敏感性，同时还最大限度地减少了反射和表面损失。使用 200-500 µm 厚的薄膜，该方法用于测量 PPXC 在 330-3300 nm 波长范围内的吸收系数。发现系数从 0.025 毫米开始在光谱上变化超过两个数量级^-1在 1562 nm 到 7.7 mm ^-1在 3262 nm。这些吸收测量可以帮助设计基于 PPXC 的传感器和波导。该方法可用于测量其他薄、低损耗材料的吸收系数，特别是那些难以获得厚样品的材料，例如以与 PPXC 类似的方式从气相沉积的其他聚合物。