How to create super bright laser beams

[planters]

I just looked at the redacted combiner again. It's a diffractive element, but I still think a prism(s) are going to prove better if they can be made to work.

[flecom]

Oclero is single mode.

wat?!

1W single mode?!

you have no idea how much I wish... if I could build a 8W red 4+4 single modes... oh sweet jeebus... I finally would not "need MOAR photons"

I just want more RED... my dream is to have at least 8~12W of red in my projector

[mixedgas]

Planters, read your PM, I have an alternative.

Steve

[jors]

Oclaro 1w single mode? it seems not possible at this power. Could you share info source please?
thanks!

Do you notice that the dispersion increases as you rotate the angle of incidence and then just before the angle becomes too low that the dispersion is maximum? I will look at another glass like BK7 (calculate it) and if the dispersion is somewhat less than the SF-11 then not important, but if the calculations show that the SF-11 should be MUCH more effective then it might be worth the risk that you aren't using the best available prism and I'll pick one up. Don't forget, if this gets close we can always use two prisms in series.

Also, at maximum dispersion, do you notice any distortion of the far field spots? There is a finite bandwidth for each beam and the prism will be stretching the spots in the same direction as the dispersion. Hopefully, this is a lot less.



This occurred to me about 2 seconds after I read about logsquared's first experiment. But, for what it's worth those images have convinced me that this can be done and if it can be done...I love challenges.


To make this more exciting, I think someone posted that the anticipated 1W Oclero is single mode.

[masterpj]

It is possible.
I think I posted it and I heard it from a very reliable source.
If not then you now hear it from me as well

[planters]

Peter,

I think it was from you I heard this. I'm hopeful, but an evolution of their 700mW multimode to 1,000mW seams reasonable. At last year's P. West conference they told me that they expected to have released several new red diodes by the next annual conference. A higher power single mode is likely. 1W?

I just want more RED... my dream is to have at least 8~12W of red in my projector

Your busted! You're an addict. You know how I know? Despite the prospect of a huge 8-12 W of red you still had to add..."at least".

I will PM Steve and I plan to order a few single mode diodes to characterize. I have some mounts, a few spare 2mm, Dave collimators and some drivers. I will use the spectrograph to evaluate the bandwidth as this is actually the true limit on the possible success of this work. I will set up a multi-stage temperature chamber to measure the wavelength variation with temperature of these diodes, but I suspect it will be close to the 0.25nm/C I have seen when testing the P73's and the 0.22nm/C that has been published. A table of bandwidth and wavelength at various temperatures will be very useful. It is also possible that multi-mode is still a candidate for this technique as well.

Only if the ratio of the wavelength spread to bandwidth is large enough can the diode beams be shifted more than they are distorted. In the purpose built , Bragg stabilized IR diodes that are used for WDM into very bright direct diode beams, the Brag grating is a wavelength narrowing/selecting replacement for one of the two cavity mirrors. They need a very narrow wavelength for each beam so that each diode can be distinct from its many neighbors. The combiner is a challenge but not a deal breaker. Andy is using a transmissive diffraction element that is probably blazed and coated to operate at close to the 630nm wavelength. The losses due to the higher orders are a drag, but they are a fixed ratio and can be treated as overhead. Prisms avoid this, but the lower dispersion may be their downfall, maybe not.

[logsquared]

I did see some anamorphic widening of the spots. Maybe 4X. I didn't make an actual measurement last night. I didn't check but it seems to reason that the near field would be proportionally smaller allowing the use of a cylindrical telescope to "fix" the expansion after the prism. I will take some better measurements later.

[planters]

That could be a problem. I suspect that the widening is not due to an anamorphic effect, but due to dispersion. However, if the near field is in fact significantly narrower in the same axis then you are probably correct and this could be remedied with a cylinder pair after the prism.

[logsquared]

I looked at this again. It does appear to be mostly an anamorphic effect. I am sure there is a small amount of "spectral smearing". I am not sure what the line width of the SM diodes is. But if the dispersion is around 20-25urad per nm, then even a 5nm line width should only increase the size by 30% or so.

The 170mw spec sheet shows ~633nm at 0deg and ~641 at 40deg. I think the number of same diodes able to be combined will have to due with the variation in the sample we get. If they all lase about the same then maybe 638 + 642 + 650? Or maybe just 4 of the p73s.

I look forward to seeing the spectrometer results of a few samples.

I really think this is practical. I don't think temp regulation will be as critical as one might think at first. Especially with around 4 diodes. Slight variations will not cause the spots to become completely misaligned. I believe it will be more challenging mechanically due to the tight tolerances and long lever arms between optics.

[mixedgas]

If the diodes are too close in wavelength you may see injection locking of any two adjacent diodes. Nothing a quarter waveplate fragment won't cure.

Steve