Now, a team of scientists from Stanford University in the USA have exploited a fundamental relationship in optical physics, the Kramers–Kronig (KK) relations, in order to make the skin of a mouse transparent (see picture), allowing its internal organs to be observed (Z. Ou et al. Science https://doi.org/10.1126/science.adm6869; 2024).

The KK relations mean that the wavelength dependence of the real and imaginary parts of the refractive index of a medium are fundamentally linked and mathematically related to each other. In essence, this means that the resonance frequency and spectral shape of optical absorption have a direct impact on the refractive index and can be used to manipulate its value.

中文翻译：

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折射率工程使皮肤透明

KK 关系意味着介质折射率的实部和虚部的波长依赖性在根本上是相互关联的，并且在数学上是相互关联的。从本质上讲，这意味着光吸收的谐振频率和光谱形状对折射率有直接影响，可以用来操纵其值。