Metrologic ML855 HeNe Laser

On Wednesday, September 11, 2013 3:57:18 PM UTC-4, Samuel M. Goldwasser wrote:

ggherold@gmail.com writes:
On Tuesday, September 10, 2013 5:04:12 PM UTC-4, Samuel M. Goldwasser wrote:

ggherold@gmail.com writes:







On Tuesday, September 10, 2013 3:02:50 PM UTC-4, mpre...@gmail.com wrote:



On Tuesday, September 10, 2013 12:58:55 PM UTC-4, tm wrote:
snip previous stuff
Thanks all. I'll pop it open and hook in a rocker switch or something like that (when no students are around, of course). Maybe I'll get lucky and the tube will still work. Otherwise, I'll talk to some friends in labs about a Helium soak.



Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.
Actually quite a lot.
Hi Sam, What kind of things? We sell both a HeNe and a diode laser with our interferometery apparatus.

http://teachspin.com/instruments/moderni/index.shtml
The HeNe has a fixed wavelength.... and as it warms up you can watch the coherence length 'swish' around as the different longitudinal modes cross over the gain curve. But that seems like a bit of an esoteric difference for the 'normal' high school laser application.

What else do you have in mind?

There's a lot one can do with respect to the longitudinal modes, though

perhaps that is a bit of a stretch for an intro to lasers in high school.



But one can do some nice interferometry experiments with not much additional

equipment.
In fact, I see you your Web site that you do some of these things.
A Fabry-Perot with a common random polarized HeNe laser is a work of art. ;-)

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?

The beam quality is also a lot better than most diode lasers (divergence,

beam profile).



With some you can put another mirror in front or in back of the laser

(if accessible) and get 1 or more of the other HeNe wavelengths.
Yeah there are lots of fun things if you allow for access to the cavity. I recall fondly an argon laser in grad school, that was equipped with a grating and mirror on one side... you could tune through all the Argon lines. There is a certain beauty in the 'pure' blue colors.
I can go on and on.....
Contact me directly via repairfaq.org if you'd like.

Thanks Again,

George H.

--

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Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/

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George H.



If it is less than about 30 years old, the tube is hard-sealed and

doesn't really leak. An ML855 could be function like new



Bypasss or replace the switch and see what happens.



Just be careful of the line voltage and high voltage inside!

 

On Wednesday, September 11, 2013 3:58:24 PM UTC-4, Samuel M. Goldwasser wrote:

ggherold@gmail.com writes:



On Tuesday, September 10, 2013 5:36:41 PM UTC-4, Roger wrote:

"Cydrome Leader" wrote in message news:l0ngg0$raq$1@reader1.panix.com...

<snip>

Shaun

Hi Shaun, Certainly the beam profile is better in a HeNe.



I'm not sure what you mean by 'more coherent', but for the few diode lasers I've looked at - compared to the short cavity HeNe that I have, the diode lasers had a longer coherence length.

(Which struck me as a bit weird the first time I saw it... I had this mistaken belief that the coherence length was related to the cavity length.)

I'm not sure if the long cavity HeNe's have a longer or shorter coherence length when compared to the short cavities... Perhaps Sam will educate us.



George H.
It's a crap shoot. Some diodes have exception coherence length but
many/most are very short.

OK that's good to know. It'd be nice if someone had a list of good diode lasers. The one we use is from US lasers M650-5I. ~$33 from digikey. We have a couple of others but I never looked at the coherence length.

George H.

--

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

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[chuck]

On Wed, 11 Sep 2013 21:32:45 -0500, "Shaun" <stereobuff07@gmail.com>
wrote:

"chuck" wrote in message news:cvr03998igu8almlenkqg6mkbktc9fneqv@4ax.com...

09/10/2013On Tue, 10 Sep 2013 23:41:52 +0200, Leif Neland
leif@neland.dk> wrote:

Roger kom med denne ide:

You'll also find a new keyswitch from digikey or newark will cost less
than talking to a locksmith.
-----------------------------------------------------------------------------------------------------------------------------
I've worked with HeNe tubes before. The ones I've seen are a foot to 1.5
feet in length; they are usually 1 milli-watt to 5 milli-watts laser
output
power. You would not want to get the beam directly in your eye, it could
cause some damage. I have heard that the eye very quickly turns to avoid
being damaged though.

Sign: Don't look into laser with remaining good eye.


I worked for a company in the mid 80s that sold Pioneer Laser Disc
players. A high school kid came in one day who experimented with the
laser tubes from these players. He had holes burnt into the iris of
one of his eyes. Chuck
------------------------------------------------------------------------------------------------
Bullshit!

A read laser does not have that much power. If it was a CD Burner - then
that could happen. With a regular CD player, the laser might damage the
Retina which is at the back inside of the eye ball, it converts what we see
into a signal that our brain decodes as an image.

I would still like to know why it is allowed that anyone can buy a handheld
diode laser under 5 milliwatts without any safeties or adult supervision.
They can do lots of damage!

Roger

The kid did have holes in his iris, maybe he experimented with other
more powerful lasers that I didn't know about. Chuck

 

[Samuel M. Goldwasser]

ggherold@gmail.com writes:

On Wednesday, September 11, 2013 3:57:18 PM UTC-4, Samuel M. Goldwasser wrote:
ggherold@gmail.com writes:
On Tuesday, September 10, 2013 5:04:12 PM UTC-4, Samuel M. Goldwasser wrote:

ggherold@gmail.com writes:







On Tuesday, September 10, 2013 3:02:50 PM UTC-4, mpre...@gmail.com wrote:



On Tuesday, September 10, 2013 12:58:55 PM UTC-4, tm wrote:
snip previous stuff
Thanks all. I'll pop it open and hook in a rocker switch or something like that (when no students are around, of course). Maybe I'll get lucky and the tube will still work. Otherwise, I'll talk to some friends in labs about a Helium soak.



Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.
Actually quite a lot.
Hi Sam, What kind of things? We sell both a HeNe and a diode laser with our interferometery apparatus.

http://teachspin.com/instruments/moderni/index.shtml
The HeNe has a fixed wavelength.... and as it warms up you can watch the coherence length 'swish' around as the different longitudinal modes cross over the gain curve. But that seems like a bit of an esoteric difference for the 'normal' high school laser application.

What else do you have in mind?

There's a lot one can do with respect to the longitudinal modes, though
perhaps that is a bit of a stretch for an intro to lasers in high school.
But one can do some nice interferometry experiments with not much
additional equipment.

In fact, I see you your Web site that you do some of these things.
A Fabry-Perot with a common random polarized HeNe laser is a work of art. ;-)
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

--
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.

 

On Thursday, September 12, 2013 4:10:39 PM UTC-4, Samuel M. Goldwasser wrote:

ggherold@gmail.com writes:



On Wednesday, September 11, 2013 3:57:18 PM UTC-4, Samuel M. Goldwasser wrote:

snip stuff to get rid of double spaces

Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.

Actually quite a lot.

Hi Sam, What kind of things? We sell both a HeNe and a diode laser with our interferometery apparatus.



http://teachspin.com/instruments/moderni/index.shtml

The HeNe has a fixed wavelength.... and as it warms up you can watch the coherence length 'swish' around as the different longitudinal modes cross over the gain curve. But that seems like a bit of an esoteric difference for the 'normal' high school laser application.



What else do you have in mind?

There's a lot one can do with respect to the longitudinal modes, though

perhaps that is a bit of a stretch for an intro to lasers in high school.

But one can do some nice interferometry experiments with not much

additional equipment.



In fact, I see you your Web site that you do some of these things.

A Fabry-Perot with a common random polarized HeNe laser is a work of art. ;-)

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

OK you may like this, I have only a few youtube videos.
http://www.youtube.com/watch?v=geQVSrXN3tE
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.

--

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.

 

[Samuel M. Goldwasser]

ggherold@gmail.com writes:

On Thursday, September 12, 2013 4:10:39 PM UTC-4, Samuel M. Goldwasser wrote:
ggherold@gmail.com writes:



On Wednesday, September 11, 2013 3:57:18 PM UTC-4, Samuel M. Goldwasser wrote:

snip stuff to get rid of double spaces

Well if that doesn't work. What's a HeNe do, that you can't do with a red diode laser? ~$10 or so.

Actually quite a lot.

Hi Sam, What kind of things? We sell both a HeNe and a diode laser with our interferometery apparatus.



http://teachspin.com/instruments/moderni/index.shtml

The HeNe has a fixed wavelength.... and as it warms up you can watch the coherence length 'swish' around as the different longitudinal modes cross over the gain curve. But that seems like a bit of an esoteric difference for the 'normal' high school laser application.



What else do you have in mind?

There's a lot one can do with respect to the longitudinal modes, though

perhaps that is a bit of a stretch for an intro to lasers in high school.

But one can do some nice interferometry experiments with not much

additional equipment.



In fact, I see you your Web site that you do some of these things.

A Fabry-Perot with a common random polarized HeNe laser is a work of art. ;-)

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

OK you may like this, I have only a few youtube videos.
http://www.youtube.com/watch?v=geQVSrXN3tE
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.