Frequency Stability: What Does 2 Parts in 10E10 Mean?

[Stu165]

Does anyone know what it means to say that the frequency stability of a laser is 2 parts in 10E10, I gather that it means that the frequency shifts 0.02nm each side of the mean wavelength. But I can't find any resources that use the term parts.

 

[Claude Bile]

The shift is usually expressed as a normalised shift w.r.t. the central laser frequency.

$$\frac{\Delta\nu}{\nu_0}$$

This quantity is dimensionless and thus has no units.

Claude.

 

[Stu165]

I know that equation and all the coherence stuff, it's just the terminology of 2 parts in 10e10, has thrown me and how to get the shift from that.

 

[Claude Bile]

Well,

$$\frac{\Delta\nu}{\nu_0} = 2 \times 10^{-10}$$

If you know the central frequency of the laser, you can figure out the exact amount of shift.

Claude.