More optics

1. Jan 7, 2006

Beer-monster

This is probably a stupid question but I'm having a small problem with an optics issue, and it keeps coming up in past exams.

Most of the formulae I know for things like coherence length and number of modes in a laser involve the frequency spread (linewidth) of the laser $$\Delta \nu$$

However the question give me the linewidth or spectral width as a wavelength e.g $$\Delta \lambda = 0.002 nm$$ along with the working wavelength $$\lambda = 633 nm$$.

Can anyone tell me how I can get from the linewidth to the frequency spread, I've tried various things (such as dividing c by the variance etc) but can't get anything that matches the answers when I follow through.

Thanks

Incidently does anyone know an online source (or possible a good textbook) for basic non-linear optics/lasers? There have been questions on deriving equations for growth of second harmonics etc and it polarisability, and I'm lost.

2. Jan 7, 2006

George Jones

Staff Emeritus
What happens if you use $\nu = c \lambda^{-1}$ and

$$\Delta \nu = \left| \frac{d \nu} {d \lambda} \right| \Delta \lambda.$$

Regards,
George

Last edited: Jan 7, 2006
3. Jan 7, 2006

Beer-monster

That worked, thanks George.

Just trying to identify and fill the gaps in my optics knowledge before my upcoming exam.

There's a few gaps but less than I expected

4. Jan 7, 2006

George Jones

Staff Emeritus
Good luck!