Hi all, Recently I am reading an introduction on using laser to create the so-called optical lattices and a periodic potential to trap the atoms or as a grating, some applications like to act on the cold atoms. I don't have much background on laser but there are few concepts I don't understand. It is said that the laser is working on single mode and have a certain wavelength (780nm) and frequency ##\omega_L## 1) I wonder when it means frequency ##\omega_L##, does it mean the resonant frequency in the chamber during lasing? If so, what is the typical value for that and how big is it comparing to the atomic resonant frequency (I mean magnitude of order)? I did some search, it seems that the atomic resonant frequency is usually in GHz but most material only tell the wavelength of the laser but not the frequency 2) The article said the laser propagating along one direction and then reflected by a mirror so to form the standing wave, which plays the role of optical lattice. As I learn in other text, the standing wave has the form ##f(x,y,t) = A\cos\omega t\sin(k_x x + k_y y)## I think ##k_x## and ##k_y## are the wave vector related to the wavelength of the laser, which used to form the spatial period of the lattice, right? So is the ##\omega## here stands for the laser frequency? That means the amplitude of the lattice is changing by time? If the laser frequency is so high, what's the net effect of the lattice? I mean will the lattice amplitude stay as an average value because of high frequency or what?