Thanks Iobaz for all your informations, I will contact those holographers.
By the way, what are the maximum power for laser diodes usable for holography ?
There are 100 - 150 mw / 405 nm / 532 nm and 650 nm diodes available on ebay, some are TEC cooled and stabilized, far to be just a simple pointer but I have read with power superiors to 20 mw, many problems can occur like instability and jumping mode:
http://www.ebay.com/itm/405nm-50mW-Blue ... 2749.l2649
or
http://www.ebay.com/itm/200mW-532nm-Gre ... 2749.l2649
Of course, those lasers are TEM00, stabilized, cooled, but is it possible to use them in holography ? (the sellers tell me "yes, of course !")
Thanks by advance,
Pierre
Multiplex with analog transparency slides ?
Re: Multiplex with analog transparency slides ?
If there is no bold statement that the laser is single longitudinal mode (SLM) only, it is a matter of luck. Some diodes might work fine, others (of the same type, even from the same batch) do not. You can check W's laser projects page for a lot of useful tips: http://hololaser.kwaoo.me/
Sometimes the seller can talk about bandwidth or coherence length. Bandwidth should be smaller than about 1 GHz for holography, which results in coherence length about 20 cm; the best lasers can be say 5 MHz, which is many meters of coherence length. Coherence length tells you maximum depth of your holograms. Again, if the seller does not mention bandwidth, the laser is likely not useful for making holograms.
Long story short: is the manufacturer claims SLM, the price is appropriate, read "high", say 10,000 USD for a new one. Otherwise, you should assume it is not SLM. If you want to play with laser electronics, you can build a setup that will try to keep SLM, but it is far from easy. If you just want to make holograms, buy a dedicated laser. Check Phils's posts here (aka 142laser) or contact him directly for an offer. I believe that Dave Battin (aka holomaker) makes SLM lasers suitable for holography; I think he is more active on the facebook forum, look there.
Anyway: the cheapest "moderately powerful" (~ 100 mW) lasers are green, say about 1000-2000 USD for an used one.
The same power in red is much more expensive, if you want a "plug and lase" solution. Anyway, there are tips how to make a nice 100 mW red laser from a DVD burner laser diode. I don't know how difficult it is. Used He-Ne lasers can be purchased for about 300-500 USD, but expect about 10-20 mW.
Blue is expensive in any power, say twice or more than green.
These are just my observations, people like Phil will tell you more reliable numbers.
Sometimes the seller can talk about bandwidth or coherence length. Bandwidth should be smaller than about 1 GHz for holography, which results in coherence length about 20 cm; the best lasers can be say 5 MHz, which is many meters of coherence length. Coherence length tells you maximum depth of your holograms. Again, if the seller does not mention bandwidth, the laser is likely not useful for making holograms.
Long story short: is the manufacturer claims SLM, the price is appropriate, read "high", say 10,000 USD for a new one. Otherwise, you should assume it is not SLM. If you want to play with laser electronics, you can build a setup that will try to keep SLM, but it is far from easy. If you just want to make holograms, buy a dedicated laser. Check Phils's posts here (aka 142laser) or contact him directly for an offer. I believe that Dave Battin (aka holomaker) makes SLM lasers suitable for holography; I think he is more active on the facebook forum, look there.
Anyway: the cheapest "moderately powerful" (~ 100 mW) lasers are green, say about 1000-2000 USD for an used one.
The same power in red is much more expensive, if you want a "plug and lase" solution. Anyway, there are tips how to make a nice 100 mW red laser from a DVD burner laser diode. I don't know how difficult it is. Used He-Ne lasers can be purchased for about 300-500 USD, but expect about 10-20 mW.
Blue is expensive in any power, say twice or more than green.
These are just my observations, people like Phil will tell you more reliable numbers.
Re: Multiplex with analog transparency slides ?
I've started to build a Michelson interferometer in my cellar (with sand on the ground, it's a very old house). I have used a red laser diode (4 mw) from Integraf so, I'm sure the laser is OK.
2 mirrors (front surface) and 1 50/50 beam splitter, I have followed the advices from Integraf to set the optics, 4 cups with sand and clothespins, the two laser dots come together on the screen, I use a microscope lens to expand the laser ray but I see very few or no interfranges in this case. There are many others but they come from each ray and have nothing to do to interferences. Once my Michelson interferometer will be fixed, I will start to create single beam hologram with the integraf kit.
Pierre
2 mirrors (front surface) and 1 50/50 beam splitter, I have followed the advices from Integraf to set the optics, 4 cups with sand and clothespins, the two laser dots come together on the screen, I use a microscope lens to expand the laser ray but I see very few or no interfranges in this case. There are many others but they come from each ray and have nothing to do to interferences. Once my Michelson interferometer will be fixed, I will start to create single beam hologram with the integraf kit.
Pierre
Re: Multiplex with analog transparency slides ?
Michelson interferometer is very sensitive to alignment.
1. Set up the diode. Everything is easier if the ray is parallel to the floor. Take for example a bottle, put it on the floor, make mark on it and make sure that the laser spot is exactly on the mark in any distance.
2. Take one mirror and put it about 1 meter from the laser. Align the mirror so that the beam is almost reflected back to the diode. It is not good if the reflected beam enters laser cavity - misalign it a little.
3. Put a beamsplitter about 0.5 m from the diode in such a way that the beam crosses it in its centre. The beam/beamsplitter angle should be approximately 45 degrees, you need not to be too precise.
4. Place the second mirror to the beam reflected off the splitter 0.5 m from the splitter - try to keep both distances splitter-mirror approximately the same. Align the mirror so that the beam returns to the splitter and travels along the first ray. Place a screen to the double ray bundle, say 1 meter from the splitter (you can go farther, no problem). If the interferometer is perfectly aligned, then you should see just one dot. If it is misaligned, you see two spots. I think it is the best if the interferometer is slightly misaligned so that you almost see two spots.
5. Place a lens (a singlet is fine, microscope objective is overkill and harder to align) between the splitter and the screen. The spot on the screen should be expanded to an area a few centimeters across. It will not be clean, you will see many interference fringes that originate in many parts of the interferometer. And now the trick. Wait a few seconds, say 20, and then slightly (!!!) tap on the floor. If some pattern in the spot blurs and then reappears, your Michelson interferometer works.
If it does not work, check if your power supply is stable, batteries are preferred. Check if there is no noise, there should be absolute silence in the room. Try to make splitter and mirror fixings more robust. You can also take a photograph of the setup and post it here - maybe someone notices a problem.
Petr
1. Set up the diode. Everything is easier if the ray is parallel to the floor. Take for example a bottle, put it on the floor, make mark on it and make sure that the laser spot is exactly on the mark in any distance.
2. Take one mirror and put it about 1 meter from the laser. Align the mirror so that the beam is almost reflected back to the diode. It is not good if the reflected beam enters laser cavity - misalign it a little.
3. Put a beamsplitter about 0.5 m from the diode in such a way that the beam crosses it in its centre. The beam/beamsplitter angle should be approximately 45 degrees, you need not to be too precise.
4. Place the second mirror to the beam reflected off the splitter 0.5 m from the splitter - try to keep both distances splitter-mirror approximately the same. Align the mirror so that the beam returns to the splitter and travels along the first ray. Place a screen to the double ray bundle, say 1 meter from the splitter (you can go farther, no problem). If the interferometer is perfectly aligned, then you should see just one dot. If it is misaligned, you see two spots. I think it is the best if the interferometer is slightly misaligned so that you almost see two spots.
5. Place a lens (a singlet is fine, microscope objective is overkill and harder to align) between the splitter and the screen. The spot on the screen should be expanded to an area a few centimeters across. It will not be clean, you will see many interference fringes that originate in many parts of the interferometer. And now the trick. Wait a few seconds, say 20, and then slightly (!!!) tap on the floor. If some pattern in the spot blurs and then reappears, your Michelson interferometer works.
If it does not work, check if your power supply is stable, batteries are preferred. Check if there is no noise, there should be absolute silence in the room. Try to make splitter and mirror fixings more robust. You can also take a photograph of the setup and post it here - maybe someone notices a problem.
Petr
Re: Multiplex with analog transparency slides ?
Thanks Petr,
I think I have successfully built the Michelson interferometer.
Here is a picture of my installation (the table is too small et not enough stable I think, I will create later a isolation free table with inner tubes, carpets and ciment:
http://www.furrylight.com/holography/IMG_0058.MOV
There is some dust in the air (the ground is made from sand) with explain probably the variations of the laser / interferences on the last video... But the stability seems not excellent, but maybe it's enough ? I'm not sure. The pictures and video has been made with an iPhone SE, the camera is not very good in the dark.
What do you think about the interferometer ?
Pierre
I think I have successfully built the Michelson interferometer.
Here is a picture of my installation (the table is too small et not enough stable I think, I will create later a isolation free table with inner tubes, carpets and ciment:
http://www.furrylight.com/holography/IMG_0058.MOV
There is some dust in the air (the ground is made from sand) with explain probably the variations of the laser / interferences on the last video... But the stability seems not excellent, but maybe it's enough ? I'm not sure. The pictures and video has been made with an iPhone SE, the camera is not very good in the dark.
What do you think about the interferometer ?
Pierre
Re: Multiplex with analog transparency slides ?
It is difficult to recognize the correct fringes in the video, but I guess the interferometer is not working - I am 99% sure. The only way safe to recognize them is the tapping method I described earlier.
Check this video: https://www.youtube.com/watch?v=-SZSkIcEyCI
At 5:13, you can see two spots with correct fringes. They are "horizontal" (in fact, they are diagonal in the video due to camera angle) and they move slightly, which is caused by micro-movements of the setup. The spot on the right shows the fringes a bit better than the left one.
Now the problems of your setup.
First of all, build it on the floor. The table desk possibly vibrates, which completely destroys everything. Remember that a movement +-1 micrometer ruins the fringes!
Second, I do not believe that the stands do not wobble. They should be really absolutely stable. I like your idea using this piece of iron as the stands, but you must fix them. Method one: screw them or hot glue them to a thick firm base. Method two: take a box about 20-30 cm high, fill it with about 5 cm of sand, place the stands on the sand surface, and add another 10-20 cm of sand (now only the rods stand out above the sand surface). I recommend you to put the base or the sandbox on the floor with a rubber or a blanket between to absorb vibrations.
Third, using one clip as a holder may be OK (although it is not 100% sure), but two clips at once are definitely unstable (such as the beamsplitter holder on the photograph). Mirrors and the beamsplitter must be rock solid; laser holder stability is not very critical, lens stability does not matter.
Good luck and don't give up!
Petr
Check this video: https://www.youtube.com/watch?v=-SZSkIcEyCI
At 5:13, you can see two spots with correct fringes. They are "horizontal" (in fact, they are diagonal in the video due to camera angle) and they move slightly, which is caused by micro-movements of the setup. The spot on the right shows the fringes a bit better than the left one.
Now the problems of your setup.
First of all, build it on the floor. The table desk possibly vibrates, which completely destroys everything. Remember that a movement +-1 micrometer ruins the fringes!
Second, I do not believe that the stands do not wobble. They should be really absolutely stable. I like your idea using this piece of iron as the stands, but you must fix them. Method one: screw them or hot glue them to a thick firm base. Method two: take a box about 20-30 cm high, fill it with about 5 cm of sand, place the stands on the sand surface, and add another 10-20 cm of sand (now only the rods stand out above the sand surface). I recommend you to put the base or the sandbox on the floor with a rubber or a blanket between to absorb vibrations.
Third, using one clip as a holder may be OK (although it is not 100% sure), but two clips at once are definitely unstable (such as the beamsplitter holder on the photograph). Mirrors and the beamsplitter must be rock solid; laser holder stability is not very critical, lens stability does not matter.
Good luck and don't give up!
Petr
Re: Multiplex with analog transparency slides ?
Thanks Petr for your advices.
The table I used is probably unstable as you said and anyway, it's far too small. I will build a new one with wood, inner tubes for isolation and carpets for better stability. I will wait to get all the elements before starting making holograms.
About the interferometer, the fringes really scramble themselves when I touch the table and come back stable a few seconds later. I will try to make a video of this phenomenon later. By the way, I had to wait about 15 minutes for the fringes to stabilize after the interferometer was setup. But I perfectly understand my system is not optimal. This table is just not stable enough.
Pierre
The table I used is probably unstable as you said and anyway, it's far too small. I will build a new one with wood, inner tubes for isolation and carpets for better stability. I will wait to get all the elements before starting making holograms.
About the interferometer, the fringes really scramble themselves when I touch the table and come back stable a few seconds later. I will try to make a video of this phenomenon later. By the way, I had to wait about 15 minutes for the fringes to stabilize after the interferometer was setup. But I perfectly understand my system is not optimal. This table is just not stable enough.
Pierre