Orbital angular momentum wavefront velocity

[calinvass]

Is the wavefront velocity if an OAM mode 1 light beam proportional to its wavelength?
I understand that the helical structure step length gives the wavelength of the beam. In this case, a small wavelength beam would travel much slower. The problem is, f=v/λ, but now v<c and if λ is shorter then f is higher but not that much because v gets increasingly slower.

 

[Chandra Prayaga]

Is the wavefront velocity if an OAM mode 1 light beam proportional to its wavelength?
I understand that the helical structure step length gives the wavelength of the beam. In this case, a small wavelength beam would travel much slower. The problem is, f=v/λ, but now v<c and if λ is shorter then f is higher but not that much because v gets increasingly slower.

Sorry. I do not know this. But why would the small wavelength beam travel slower?

 

[calinvass]

Sorry. I do not know this. But why would the small wavelength beam travel slower?

http://www.nature.com/articles/srep26842
https://en.m.wikipedia.org/wiki/Orbital_angular_momentum_of_light
It says that for m=1, the step length is λ. The speed reduction is proportional to the step length.