andy_con
ClioSport Club Member
clio 182
So… this is a project I undertook last year, im sure a number of people know I love to play with lasers.
The technique is called wavelength division multiplexing, in simple terms its how you get lots of data down a fibre optic cable. So you combine (overlay) different frequencies of light into a single beam and fire them down a fibre. If you fire ten different frequencies of light down one fibre you have 10x times the amount of data flowing down it. So rather than dig up streets to lay more fibre cables, you increase the amount of frequencies down a single fibre.
I have no interest in fibre optic cables.
In the world of laser shows red is always an issue, not enough power or too big a beam. So what if you could use wavelength division multiplexing to combine more than one beam into a single beam? At the moment there are two options, use a polarizing beam splitter (PBS) to combine (overlay) two beams into one. Or use lots of small beams side by side to make a powerful but fatter single beam. With a PBS you are limited to two beams only and with the second option you end up with a big beam. So neither are great.
If you think about shining white light / the sun into a prism you get a rainbow out.
what they do with wavelength division multiplexing is shine different frequencies (colours) of light into a prism and combine them into a single beam. So if you could get different frequencies of red light and shine them into a prism you could get a single beam out, sounds simple!! Yeah sure…
in order for it to be worthwhile you wouldn’t want any less than 5 beams to be combined, otherwise your not going to get any decent power. Spec sheets say that with a temperature change from -10 to 60 degrees the frequency will be between 632nm and 642nm.
so in order to combine 5 diodes each would need to be 2nm apart.
In order to be able to measure the frequency of the lasers I found a second hand wavemeter on ebay in the USA. I took a massive gamble and paid £500 for it, this isn’t my site –
http://hololaser.kwaoo.me/electronics/WA2000.html
it took many hours with the help of some friends to align and get some kind of sensible reading from, but it was working. So it wasn’t £500 down the drain. This is mine in action –
next I needed a way of launching a beam down a fibre and into the wavemeter, so I made a free space fibre coupler. On the front is a brass barrel holding a lens, this enables you to focus the laser beam onto the tip of the fire optic cable. The thread on the lens is M9x0.5
the fibre plugs into the back behind the lens and this part has XYZ adjustment screws.
Then all of that was on springs and adjusters so I could move it up/down and left/right.
All the screws/adjusters were purchased from Thorlabs and were fine pitch at M3x0.2, I had to buy the matching tap ☹
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1202
once that was all sorted I then had to build a laser rig where I could control the temperature of each laser beam and steer the beams.
So started by machining up some diode holders.
On the bottom was a slot for a small tec/peltier.
On the top was a hole to insert a temperature probe so I knew the temp of each block.
on the front was an M9x0.5 threaded hole for the adjustable focusing lens
on the back was a hole to insert the diode, which is 5.6mm dia. 4x M2 holes around it for a retainer to hold the diode in place and the hole at the bottom was for another temperature probe to give feedback to the TEC drivers.
I purchased 4x tec/peltier drivers from here –
https://www.live-lasersystems.at/d/diode-tec-drivers.html
I had a few diode drivers laying around so that wasn’t an issue and I purchased 4x of these diodes –
https://sites.google.com/site/dtrslasershop/home/diodes/sharp-gh0631ia2g-185mw
I then made a rig to set it all up
so a few different power supplies on the right
bottom left is a screen that can display 4x temperature inputs
in front of the screen is the 4x tec controllers
in front of the tec controllers are the 4x diodes
to the right of the diodes is the control board for the screen that reads the temperatures.
This is everything wired up
Diodes wired to the drivers
Probe on top of each diode holder wired up to display each temp on the blue screen
Tec/peltier under each aluminium diode holder wired to the driver and the probe on the bottom rear also wired to the driver so it knows whats what.
I purchased some cheap £5 glass prisms off ebay and did some playing.
It became clear very quickly that setting the temperature below 5 degrees caused a lot of condensation build up, to the point where I would get little puddles. But if I set one diode to 5 degrees, put it through the prism and put a mark on the wall at the end of my workshop. If I then turned the temperature up to 40 degrees you could watch the beam drift across the wall maybe 5-10mm.
The wavemeter turned out to not be the right tool for what I wanted. It was unbelievable sensitive, just walking across the floor made the reading change. I also discovered it liked a really nice clean round laser beam fired into it, not a distorted messy beam from a 40 degree diode. A spectrometer probably would have been better.
So the conclusion of maybe 3 months acquiring and making parts, 2 weeks of building and 2 weeks of testing was that yes in theory you could use wavelength division multiplexing to combine more than one red beam into a single beam. But it would be very difficult to put into real work use, EG. in a laser projector for show use. It would probably end up being a pretty large setup and very difficult to keep stable (aligned).
So I sold the wavemeter and manged to get every penny back I paid for it and put the laser rig on the shelf.
The end.
The technique is called wavelength division multiplexing, in simple terms its how you get lots of data down a fibre optic cable. So you combine (overlay) different frequencies of light into a single beam and fire them down a fibre. If you fire ten different frequencies of light down one fibre you have 10x times the amount of data flowing down it. So rather than dig up streets to lay more fibre cables, you increase the amount of frequencies down a single fibre.
I have no interest in fibre optic cables.
In the world of laser shows red is always an issue, not enough power or too big a beam. So what if you could use wavelength division multiplexing to combine more than one beam into a single beam? At the moment there are two options, use a polarizing beam splitter (PBS) to combine (overlay) two beams into one. Or use lots of small beams side by side to make a powerful but fatter single beam. With a PBS you are limited to two beams only and with the second option you end up with a big beam. So neither are great.
If you think about shining white light / the sun into a prism you get a rainbow out.
what they do with wavelength division multiplexing is shine different frequencies (colours) of light into a prism and combine them into a single beam. So if you could get different frequencies of red light and shine them into a prism you could get a single beam out, sounds simple!! Yeah sure…
in order for it to be worthwhile you wouldn’t want any less than 5 beams to be combined, otherwise your not going to get any decent power. Spec sheets say that with a temperature change from -10 to 60 degrees the frequency will be between 632nm and 642nm.
so in order to combine 5 diodes each would need to be 2nm apart.
In order to be able to measure the frequency of the lasers I found a second hand wavemeter on ebay in the USA. I took a massive gamble and paid £500 for it, this isn’t my site –
http://hololaser.kwaoo.me/electronics/WA2000.html
it took many hours with the help of some friends to align and get some kind of sensible reading from, but it was working. So it wasn’t £500 down the drain. This is mine in action –
next I needed a way of launching a beam down a fibre and into the wavemeter, so I made a free space fibre coupler. On the front is a brass barrel holding a lens, this enables you to focus the laser beam onto the tip of the fire optic cable. The thread on the lens is M9x0.5
the fibre plugs into the back behind the lens and this part has XYZ adjustment screws.
Then all of that was on springs and adjusters so I could move it up/down and left/right.
All the screws/adjusters were purchased from Thorlabs and were fine pitch at M3x0.2, I had to buy the matching tap ☹
https://www.thorlabs.com/newgrouppage9.cfm?objectgroup_id=1202
once that was all sorted I then had to build a laser rig where I could control the temperature of each laser beam and steer the beams.
So started by machining up some diode holders.
On the bottom was a slot for a small tec/peltier.
On the top was a hole to insert a temperature probe so I knew the temp of each block.
on the front was an M9x0.5 threaded hole for the adjustable focusing lens
on the back was a hole to insert the diode, which is 5.6mm dia. 4x M2 holes around it for a retainer to hold the diode in place and the hole at the bottom was for another temperature probe to give feedback to the TEC drivers.
I purchased 4x tec/peltier drivers from here –
https://www.live-lasersystems.at/d/diode-tec-drivers.html
I had a few diode drivers laying around so that wasn’t an issue and I purchased 4x of these diodes –
https://sites.google.com/site/dtrslasershop/home/diodes/sharp-gh0631ia2g-185mw
I then made a rig to set it all up
so a few different power supplies on the right
bottom left is a screen that can display 4x temperature inputs
in front of the screen is the 4x tec controllers
in front of the tec controllers are the 4x diodes
to the right of the diodes is the control board for the screen that reads the temperatures.
This is everything wired up
Diodes wired to the drivers
Probe on top of each diode holder wired up to display each temp on the blue screen
Tec/peltier under each aluminium diode holder wired to the driver and the probe on the bottom rear also wired to the driver so it knows whats what.
I purchased some cheap £5 glass prisms off ebay and did some playing.
It became clear very quickly that setting the temperature below 5 degrees caused a lot of condensation build up, to the point where I would get little puddles. But if I set one diode to 5 degrees, put it through the prism and put a mark on the wall at the end of my workshop. If I then turned the temperature up to 40 degrees you could watch the beam drift across the wall maybe 5-10mm.
The wavemeter turned out to not be the right tool for what I wanted. It was unbelievable sensitive, just walking across the floor made the reading change. I also discovered it liked a really nice clean round laser beam fired into it, not a distorted messy beam from a 40 degree diode. A spectrometer probably would have been better.
So the conclusion of maybe 3 months acquiring and making parts, 2 weeks of building and 2 weeks of testing was that yes in theory you could use wavelength division multiplexing to combine more than one red beam into a single beam. But it would be very difficult to put into real work use, EG. in a laser projector for show use. It would probably end up being a pretty large setup and very difficult to keep stable (aligned).
So I sold the wavemeter and manged to get every penny back I paid for it and put the laser rig on the shelf.
The end.
lol
