Backside absorbing layer microscopy: a universal relationship between physical thickness and reflectivity
Achieving sub-nanometer axial resolution in wide-field optical microscopy for visualizing monolayers and bio-chemical processes is highly desirable in many fields. The authors of this article have proposed a new microscopy method named BALM (Backside Absorbing Layer Microscopy) that provides high contrast reflection images of monolayers. The key to this novel optical microscopy technique is the so-called ARA (Anti-Reflection Absorbing) layers. These ARA layers are made of absorbing materials, a few nanometers thick on which the sample can be deposited and imaged in an inverted wide-field microscope. Since only a thin layer of the sample that is close to the ARA layer gets imaged, the open access to the topside of the sample leaves room for various physical manipulations and probing methods to be used. The analysis presented in the current article proposes a set of new parameters to quantify the reflectivity and the thickness of the sample in the BALM technique that obtains the thickness of a sample with any refractive index profile and independent of the microscope settings.