I have a question :

what is the benefit of abrupt phase change?

for example in phase gradient metasurface (PGM) , we use arrangements of unit cells which each unit cell has dimension of subwavelength and also phase shift between adjacent unit cell is constant (for example 60 degree) therefore arrangement of 6 unit cell generate 360 degree phase coverage in about 1 wavelength dimension .

what is the benefit of this abrupt phase change ?

compare with gradual phase change ?

tell me whatever you know . i want to understand what's happening .thanks