Metrologic ML855 HeNe Laser

[Samuel M. Goldwasser]

Hi Sam, Thanks for the response. You're talking about sending the
laser into a F-P and looking at the output? A flat mirror F-P
(Etalon), a confocal curved mirror F-P, or something in between?

Generally, a confocal FP is best since it greatly simplifies alignment.

For the HeNe, the mirror Radius of Curvature (RoC) of both mirrors needs
to be less than about 50 mm so that the Free Spectral Range (FSR, or
mode spacing of the FP) is larger than the gain bandwidth of the
HeNe red transition.

One of the FP mirrors is then mounted on a piezo transducer (PZT) and
the FP is scanned rather than the laser. The PZT can be the beeper
element from a digital gizmo or less than $2 from Digikey.

More info at: http://www.repairfaq.org/sam/laserlia.htm#liasfpi

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[[email protected]]

[email protected] writes:









Generally, a confocal FP is best since it greatly simplifies alignment.



For the HeNe, the mirror Radius of Curvature (RoC) of both mirrors needs

to be less than about 50 mm so that the Free Spectral Range (FSR, or

mode spacing of the FP) is larger than the gain bandwidth of the

HeNe red transition.

One of the FP mirrors is then mounted on a piezo transducer (PZT) and

the FP is scanned rather than the laser. The PZT can be the beeper

element from a digital gizmo or less than $2 from Digikey.

More info at: http://www.repairfaq.org/sam/laserlia.htm#liasfpi

OK you may like this, I have only a few youtube videos.

I'm sending a diode laser into a confocal cavity, (20 cm mirrors)
with the cavity length set maybe 1cm short, so all the modes, don't all fall at the same wavlength. I'm then scanning the laser wavlength, and have abare CCD camera (no lens) pointing into the back end of the cavity. This video has mostly just the even modes* but the others show both odd and even..

George H.
*if you get the laser 'smack dab' down the middle you lose 'most' of the odd modes.

 

[Samuel M. Goldwasser]

OK you may like this, I have only a few youtube videos.

I'm sending a diode laser into a confocal cavity, (20 cm mirrors)
with the cavity length set maybe 1cm short, so all the modes, don't all fall at the same wavlength. I'm then scanning the laser wavlength, and have a bare CCD camera (no lens) pointing into the back end of the cavity. This video has mostly just the even modes* but the others show both odd and even.

George H.
*if you get the laser 'smack dab' down the middle you lose 'most' of the odd modes.

I assume you are seeing a combination of the laser modes (if not single
longitudinal mode) and the off-axis cavity modes. It may be possible to
determine the spectrum of the diode laser from the video but that's above
my pay grade.

--
sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: Anything sent to the email address in the message header above is
ignored unless my full name AND either lasers or electronics is included in the
subject line. Or, you can contact me via the Feedback Form in the FAQs.