Re: Monochromator

Hi Mat' -
Hi there,

Now, I'm having trouble visualizing the system that you describe. Can you describe the optical setup with some more detail?
I have a 130fs laser source @1260nm which I used to produce SHG signal @630nm.
At the laser output the beam is slightly divergent (0.03°).
This beam is focused on a probe using a fused silica lens.
The SHG signal is collected with a BK7 lens which is placed so that the beam is collimated after the lens, with a diameter of about 2.5µm.
What follow is related to the monochromator.
I plan to use another BK7 lens of focal 300mm (same focal as the monochromator collimating mirror) to get the focus on the input slit.
I will be using both the 1260nm and 630nm signal to check if the monochromator motor is properly calibrated.

To date my problem is that I am definitively not familiar with monochromators. At least as far as I've heard I should use a lens with the same focal as the collimating mirror. I would have rather used a lens with a shorter focal so that my beam is expanded when reaching the mirror!

Also, with such a small beam
diameter it would seem that the input slit is irrelevant as I suspect the beam diameter is much smaller than the slit width.
Should I then consider using the diffraction from the slit to expand my beam?

Best regards,
Mat'
.

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