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Why HeNe?

ultimatekaiser

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Yeah I know bob. He's a good guy-he actually has a couple of my former lasers in his collection somewhere. I kinda want to visit him sometime.
 



Radim

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What's the advantage of HeNe lasers these days? Is there anything they can do that diodes can't do better? Or is it just a matter of it being a cool tech? HeNe tubes definitely scream "laser" to me, much more than diodes. :)
Many advantages. Instead of mentioning all of them popping out in my head right now, I mention just one - extremely long temporal coherence length. Do you want to make a hologram of larger object? Red or green? Go for HeNe laser as cheapest and best beam quality option.

And not only holography, even further stuff where precise coherence is needed. If you went for DPSS with ring cavity design for example, you paid ($)$ $$$, but HeNe might go cheaper by order(s). In addition HeNes are known for long life and simple construction, there is no exception you can get 20+ years old laser tube from second hand still capable of high performance.
 
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paul1598419

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The guy with the laser museum (Bob Hess) contacted me earlier to share a link to his website which contains pictures of the collection. He said that he recently added laser number 400 to the collection.

I had seen the site before but it was invite only at the time, didn't know that it had been made publicly available.

https://sites.google.com/site/vintagelaserarchive/
Bob emailed me some time ago. He thought we might have met years ago as I too have been a holographer for many years now. Unfortunately, we hadn't met as I was in different parts of the country than he was. Thanks for this link as it is very informative. He has one of the best collections of lasers I've ever seen. Outside of a museum it is probably the best.
 

Radim

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The guy with the laser museum (Bob Hess) contacted me earlier to share a link to his website which contains pictures of the collection. He said that he recently added laser number 400 to the collection.

I had seen the site before but it was invite only at the time, didn't know that it had been made publicly available.

https://sites.google.com/site/vintagelaserarchive/
Awesome collection. Thanks for sharing the link, diachi. :drool: :thanks:
 

icecruncher

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my helium Neon at 612 is quite bright 2mw orange and it has such a small dot and i tested it by shining 50 feet at night and it still had better divergance than my cni 561. mine has a perfect round dot. They look amazing.

try finding anything near a 612 in color on something other than HeNe :)

Probably not going to happen :)

And if you love glass, you can't beat the look of a huge exposed glass HeNe.
 
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FRITZ HID

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try finding anything near a 612 in color on something other than HeNe :)

Probably not going to happen :)

And if you love glass, you can't beat the look of a huge exposed glass HeNe.
There really is something about that pinkish glow, isn't there? i Love looking at my 127b (i keep the cover off), long, thin, glowing bore and the gorgeous red beam! eventually i plan to get some yellow & orange optics for it as well. too bad green isn't an option for 1m HENEs. :(
 

Mattronium

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lol yeah. my oldest one is from '68 I think if I remember correctly. It's incredibly old-so old in fact it has a filament in it instead of a cold cathode.
Nice. My oldest is my Hughes 3225H-C from 1980. I've looked for HeNe's older than 1980 but didn't find any within my price range.

Relating to the original question. Another advantage of HeNe's is that, for 594nm, a dicro can be used to form an extended cavity to lase the 632.8nm and 612nm. Then one can split them through a grating and watch the mode hopping of each line, it's quit fascinating to watch.
 

cornweda

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I have been investigating holography using cheap diode lasers and have been surprised to find that some people have achieved coherence length that exceed many HeNe lasers (for example lengths greater than their optical tables). The problem seems there is a lot of hit and miss with these diodes even among the same model of diodes. Expensive diode lasers can exceed 100m coherence lengths. The beam being elliptical shape, but still single mode can be an advantage when you are making holograms of rectangular framed objects. The problem with many laser diodes is their sensitivity to small changes in current and temperature causing the frequency to shift and hop. People have been able to get good holograms (i.e. very good beam quality) from cheap laser diodes by letting the diodes warmup and using simple batteries to stabilize the current. Under rating the diode goes a long way to stabilizing the beam and can still be a higher output than a cheap HeNe laser.
 

ultimatekaiser

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I have been investigating holography using cheap diode lasers and have been surprised to find that some people have achieved coherence length that exceed many HeNe lasers (for example lengths greater than their optical tables). The problem seems there is a lot of hit and miss with these diodes even among the same model of diodes. Expensive diode lasers can exceed 100m coherence lengths. The beam being elliptical shape, but still single mode can be an advantage when you are making holograms of rectangular framed objects. The problem with many laser diodes is their sensitivity to small changes in current and temperature causing the frequency to shift and hop. People have been able to get good holograms (i.e. very good beam quality) from cheap laser diodes by letting the diodes warmup and using simple batteries to stabilize the current. Under rating the diode goes a long way to stabilizing the beam and can still be a higher output than a cheap HeNe laser.
Yes. It greatly depends on the model of diode and how it is being implemented. I very low power one being held very stable can be used for holography just fine nowadays, but that wasn't always the case. HeNes do still achieve a better beam spec overall for the price in many cases though, and have very long lifetimes-but nowadays I do feel solid state can definitely achieve far better results. the question is cost vs performance vs lifetime vs energy consumption.
 
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paul1598419

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I have been making holograms since 1980. All of mine have been done with He-Ne lasers. Now, it you can get a good single mode diode and control its temperature very precisely with a feedback loop TEC, then if you select the wavelength you want it to lase at with diffraction tuning, you can get coherence lengths in the hundreds of meters. That is much farther than you would even need to make a really good deep field hologram.

I prefer to make refection holograms as apposed to transmission ones as the latter needs a laser to reconstruct the object wave. The difference is how you set the optical bench up. To make a transmission hologram you only need to have the reference beam and the object beam hit your photographic plate from the same side. To make a reflection hologram the reference beam hits the film from the front and the object beam hits the plate from the rear. This causes an interference such that white light hitting it sets up standing waves and only the wavelength that is the same as the one that made the hologram gets through.
 
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ultimatekaiser

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Yeah I prefer the reflective method myself, but it takes alot more time and space and setup. I have a few slm lasers all throughout the spectrum, but most are fairly low power.
 

paul1598419

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Unless you are doing a huge hologram a lot of power isn't necessary. I can get a good 8 inch square hologram with about the same depth with only 10 mW. Of course the room is completely dark except for the laser. And it can only be seen during the exposure time.
 

cornweda

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My first HeNe laser I owned was in my Laser Disc player. This was one of the first consumer electronics use of a laser. This was back in the 1980's. The HeNe lasers were quickly replaced with laser diodes a few years later. One of the reasons the HeNe laser's prices dropped was the consumer use of these lasers. The same is true for the laser diode. The small size of the laser diode and the higher power outputs and much greater energy efficiencies made the laser diodes much better suited for consumer electronics.
It is not really the beam quality of the laser diodes that is the issue. We use cheap mass produced laser diodes design for consumer electronics and not high end scientific experiments. Laser Diodes can be designed with excellent beam quality with much higher efficiencies than HeNe (higher output much smaller size). Also, HeNe laser do not scale well with power output. The power output is dependant on tube length and the cost, length, weight goes up quickly. Raw laser diodes actually have a longer lifetime typical 100,000 hours.
 

paul1598419

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The type of diode lasers you are talking about are quite expensive. Even for a 20 mW laser you can shell out $10,000 for a laser that will be really good for holography. Even then you won't get a Gaussian beam which has a TEM00 mode. Then there is the problem of polarity. He-Nes are still favored for these reasons for making holograms. But, you are right that the cost of a good holographic He-Ne laser is higher than an off the shelf He-Ne laser.
 
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ultimatekaiser

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You are mostly correct. most HeNes average about 10-20K hours. diodes vary greatly with running environment and usage. I indeed still have some of the earliest HeNes ever made, including some lasedisc ones. I think my earliest one is from the mid 60s and has a hot filament. it's quite a wierd little thing.

as for my holograms, yeah I usually used to do most of my exposures at around 20mW of power. most all lasers used in holography have some method of polarization forcing.
 
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