Converting laser fwhm bandwidth in m to hz

[melcicero]

hi, pls can someone help me with converting FWHM bandwidth of a laser from metres to hertz

 

[mgb_phys]

Just from the dimensions
frequency (1/s)= speed (m/s) / wavelength (m)

 

[melcicero]

thank you but i didn't think you could directly convert fwhm bandwidth just using that, when i did it i got a bandwidth of region 10E17 Hz -does that seem a bit high from a ruby laser cavity length 0.1m?

If i post the whole question it might help. Also should i include the refractive index of the medium ie c/n=f lambda, if this is the right way to do it?

for the 0.1m cavity, n =1.8, FWHM gain bandwidth is 2E-9m
qu is: what is the longitudinal mode spacing and the number of lasing modes? i could give the spacing in either freq or wavelength but its easier to do i think in freq that's why i wanted to convert. many thanks if you can help.

 

[ahmedhelal238]

you can use the following formula

Df=c*Dlambda/Lambda^2

 

[paranormal]

To convert FWHM bandwidth of a laser from meters to hertz, we need to know the wavelength of the laser. This is because the FWHM bandwidth is directly related to the wavelength of the laser. Once we have the wavelength, we can use the formula:

FWHM bandwidth (Hz) = Speed of light (m/s) / Wavelength (m)

For example, if the laser has a wavelength of 532 nm, we can convert it to meters by dividing by 1 billion (since 1 nanometer = 1 billionth of a meter). This gives us a wavelength of 5.32 x 10^-7 meters.

Now, we can plug this into the formula:

FWHM bandwidth (Hz) = 3 x 10^8 m/s / 5.32 x 10^-7 m

This gives us a FWHM bandwidth of approximately 5.64 x 10^14 Hz.

It is important to note that this conversion assumes a Gaussian distribution for the laser beam. If the laser beam has a different distribution, the conversion may be slightly different. Additionally, FWHM bandwidth is a measure of the width of the spectral distribution, not the actual frequency of the laser. To determine the actual frequency, we would need to know the specific laser source and its operating parameters.