Laser Spectroscopy setup

shemo · Feb 22, 2015

In this setup for laser spectroscopy I have some question
1)I thought laser spectroscopy is based on using laser to zap and create a plasma of the sample, this setup only using 532nm green laser which isn't powerful to zap and create plasma.

2)why using 532nm green laser and there's a interference filter to blocks 532nm green light?

3)There's IR filter in front of laser which block infrared. how about UV? is there a need for UV filter?

4)what's a microscope objective? how's the different than a lens?

5) for lens? what kind of lens is that?

6)optic fiber, is that a regular fiver optic cable?

7) the prism looks like it bend the laser 90 degree to the sample. Shouldn't that be a mirror instead? I thought prism is used to disperse the light , not for bending the laser.

Dan Mills · Feb 22, 2015

1: A 532nm frequency doubled yag most assuredly can ablate a sample and create a plasma (Especially if the thing is Q switched), the things are after all used in laser surgery all the time.

2: You don't want reflected 532nm laser radiation reflecting off the target and saturating the spectrophotometer, hence the need for a dicro to block the 532nm light.

3: 532nm is the second harmonic of the IR yag laser line at 1064nm in the IR. As you are trying to sense the IR spectrum it is vital that no significant amount of the lasers IR fundamental leaks into the signal you are attempting to detect, this filter is there to reduce the IR leakage from the laser source. As a SHG cut non linear crystal will not produce meaningful amounts of third harmonic, there is no need to worry about UV.

4: A microscope objective is a short focal length magnifier, usually a compound lens, it both focuses the laser beam to a spot on the target and gathers the IR light from the resultant plasma.

5: That lens is just part of the fiber launch, it couples the IR into the fiber.

6: The fiber needs to pass the IR over the band of interest, have a numerical aperture compatible with the optical system and match the requirements of the spectrophotometers input port.

7:The objective here is to bend the 532nm beam to pass thru the focusing objective while allowing the IR coming back to pass to the fiber launch assembly, prism, dielectric mirror, whatever works really.

HTH.

Regards, Dan.

shemo · Feb 22, 2015

Dan Mills said:
1: A 532nm frequency doubled yag most assuredly can ablate a sample and create a plasma (Especially if the thing is Q switched), the things are after all used in laser surgery all the time.

2: You don't want reflected 532nm laser radiation reflecting off the target and saturating the spectrophotometer, hence the need for a dicro to block the 532nm light.

3: 532nm is the second harmonic of the IR yag laser line at 1064nm in the IR. As you are trying to sense the IR spectrum it is vital that no significant amount of the lasers IR fundamental leaks into the signal you are attempting to detect, this filter is there to reduce the IR leakage from the laser source. As a SHG cut non linear crystal will not produce meaningful amounts of third harmonic, there is no need to worry about UV.

4: A microscope objective is a short focal length magnifier, usually a compound lens, it both focuses the laser beam to a spot on the target and gathers the IR light from the resultant plasma.

5: That lens is just part of the fiber launch, it couples the IR into the fiber.

6: The fiber needs to pass the IR over the band of interest, have a numerical aperture compatible with the optical system and match the requirements of the spectrophotometers input port.

7:The objective here is to bend the 532nm beam to pass thru the focusing objective while allowing the IR coming back to pass to the fiber launch assembly, prism, dielectric mirror, whatever works really.

HTH.

Regards, Dan.

Great, Thanks, It's going to take awhile to digest all these.
I have seen sample putting into a glass container in this setup, like some type of liquid.
now how can sample be zapped by laser if sample in a glass container?

Can a diode laser from DVD recorder be used for this 532nm laser?

Laser Spectroscopy setup

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