question on merging two beams of same Wavelength

**zerowaitstate** · 05-07-2009, 10:31

Hey guys i'm still a little way off masacreing my chinese rgb projector, but am wondering hgte following.

I have CNI MBL50 (suposedly 50mw blue) and a supposedly 100mw CNI Blue (sticker is cut where model number is but Serial number is intact)

Q - If i build a YAG bed can, i combine the output of two 50mw blue diodes? and will this give me 100mw? or is it likley to be some lower % figure (if so what would be a reasonable figure to estimate) I ask the question as i will want to balance the output and may need to purchase alternate Red diode to get a nice white beam.

Any help or advice greatly appreciated.

**buffo** · 05-07-2009, 10:47

There is one* way to combine a pair of beams of the same frequency, and that is to use a polarizing beam-splitting cube in reverse. This requires that both lasers have a polarized beam to start with. You rotate one laser so the beam is vertically polarized, and the other so it's horizontally polarized. Then you pass them through the cube, and they will be combined into a single output beam which will be randomly polarized. This trick only works once.

Adam

* technically there is a second way, but it's fantastically expensive, nearly impossible to align, and wholly impractical for all but the most well-financed research facility. If you think you've got what it takes to build a mode-locked pair of lasers and align the polarization and phase angles to at least three significant figures, then you *might* get lucky. But you're dealing with quantum effects here, and it's going to drive you mad. No way it's going to work with off-the-shelf DPSS lasers, but it has been done at least once before, using very precise HeNe lasers. Here's a link to a discussion on alt.lasers if you're really curious...

**mixedgas** · 05-07-2009, 11:01

[QUOTE=buffo;95122]There is one* way to combine a pair of beams of the same frequency, and that is to use a polarizing beam-splitting cube in reverse. This requires that both lasers have a polarized beam to start with. You rotate one laser so the beam is vertically polarized, and the other so it's horizontally polarized. Then you pass them through the cube, and they will be combined into a single output beam which will be randomly polarized. This trick only works once.

Or use a half wave plate and not have to rotate one laser, but you still need the cube.

**olive13** · 05-07-2009, 13:01

hi everybody
i am a new member on this forum but not on laserfreak french section.

for your question zerowaitstate,
you just need a pbs cube optimised for blue wavelenght 473nm
you must prefer reflexion>98% way for the most powered(100mw).
You can see pictures.It's my first project 1.5W RGB with 2 blue dpss :laserwave and cni.
Good luck

**Laser Ben** · 05-07-2009, 18:04

WOW! Olive! Nice work! That is a truly professional looking system you've got there!

**olive13** · 05-08-2009, 01:26

Thank you Laser Ben, In fact it's a originally "Laserworld RGB Projector -500mw with TTL modulation "
i have modfied this one to 1.5w RGB with one 473nm CNI (20mwTTL-builder) upgraded to 180mw analogue modulation(CNI PSU-III-OEM tuned ttl to analogue) and Original LD changed by a 3w 808nm.
Add - new dpss laserwave 532nm+473nm.
Red laser module is home made with four (2X658nm -200mw and 2X642nm -150mw opnext diodes).
Lot of parts changed - Dichroic filters, galvo mirrors, low loss glass-window.......(medialas components)

Zerowaitstate, PBS separates or combines laser beams into two different polarization beams - You can see better the assembly of my two 473nm DPSS with different polarization - Reflectance or Transmittance way on the first picture.

Regards

Oliver