Atomically flat vs Optically flat

[onqun]

Hello,

What is the difference between optically flat surface and atomically flat surface?

 

[Yuqing]

Atomically flat surfaces would suggest that the surface is flat on an atomic level which is a nearly if not completely impossible accomplishment. Optically flat suggests that the surface is flat to the human eye such as glass or ice. Note that even though glass and ice looks flat and smooth to the naked eye, they are in fact covered with numerous molecular impurities and are thus not atomically flat.

 

[pallidin]

Optically flat suggests that the surface is flat to the human eye such as glass or ice.

No. Here is one definition: http://en.wikipedia.org/wiki/Optical_flat

"Optical flats are optical-grade glass structures lapped and polished to be extremely flat on one or both sides, usually within a few millionths of an inch..."

 

[Redbelly98]

Commercial optics have surfaces specified to be flat to within some fraction of a wavelength. Typically this is between 1/4 to 1/20 of some specified (usually visible) wavelength. As such, the flatness is on the scale of 30 to 140 nm.

Since it is impossible to be flatter than the size of an atom, I presume "atomic flatness" means flat on the scale of an atom, or roughly 0.1 nm.

 

[sardar]

An optically flat surface refers to a surface that is smooth and flat to the naked eye, with no visible imperfections or irregularities. This type of surface is often used in optics and microscopy, where the slightest deviation from flatness can affect the accuracy of measurements or distort images. Optically flat surfaces are typically measured in units of light waves, with the most common standard being 1/4 of a wavelength of green light (546 nm).

On the other hand, an atomically flat surface refers to a surface that is smooth and flat at the atomic level, with no variations or defects in the arrangement of atoms. This type of surface is extremely precise and is often used in nanotechnology and materials science. The flatness of an atomically flat surface is typically measured in units of angstroms (10^-10 meters), which is the size of an atom.

In summary, while optically flat surfaces are smooth and flat to the naked eye, atomically flat surfaces are smooth and flat at the atomic level. Optically flat surfaces are important for precise optical measurements, while atomically flat surfaces are crucial for precise material properties and nanoscale applications.