Blue beam quality

[The_Doctor]

Nice. Looks quite tidy inside, that one. Do you have any advice about the interaction between preset pots RwI and RwL and the little bi-colour LED? I never figured out the extent of what's going on there. Also, is that front panel pot working with them, or instead altering brightness by hacking into the soft start circuit?

Cool gallery, that's good, getting that far into one of those laser heads. The sealed LambdPro heads make me nervous of going in, so I haven't done it. I might if my 100 mW dies though, I'd want to make that go again. I also managed to read most of the chip numbers with dabs of white spirit and a metal halide lamp and a strong magnifier (old Zenit camera lens). All the 8-pin DIL types anyway, the 14 pin IC still isn't identified in that PSU. Let me know if you want that info. It might be too specific to be useful, but nm... it's yours if you want it.

[Zoof]

It took quite a bit of work rebuilding that one, if you ever need to take yours apart let me know if you need any info.
Actually this is no longer mine, I sold it because I could not leave it alone and made thing better then worse and better and worse again. Kinda drove me mad. Now some other Dutch laserist is having fun with it.
Looking at the pcb, there are some similarities. In my pic there are three pot visible and there was a fourth one that was replaced by the external pot. Just to the upper left of the bottom pot you can see the empty spot for it. The external pot trims the brightness of the laser. Just before the max setting the red led next to it would come on. This led indicates that the current was being limited to protect the diode. The limiting / max current was set by the bottom pot (near the front panel). The maximum this driver would do was 1.5A, the new diode would go up to 1.6A so I was pretty safe there.
The two pots at the top (near back panel) control the TEC circuit. This was pretty much guess work. Don't recall much about the two color led.

Looking at your pics I would guess that your TEC control circuit has only one pot... The others probably have the same functions as in mine... but its just guesswork

hope this is of use

cheers
Z.

[sbk]

From what I have heard, blue dpss have a problem with noise. I think mine does. When I scan it off this motorized first surface mirror tha makes a fan or liquid sky effect, you can see it. It's kinda hard to explain, other colors look like a nice solid line, the blue looks like it has an off ossilation, or noise in the scanned beam, kinda like a sound wave. I don't think it looks bad, just noticable.

I just installed my Lasever 100mW blue in my projector, and I can notice this "noise" too when the beam is moving fast... The blue beam is the only to do that.
Hopefully it's not very annoying, only noticeable near the beam. Just when you do a tunnel, it isn't perfect smooth...
Anyway, I'm very happy with the quality of the Lasever (from Dave), the driver is very well built (in SMD), the beam quality and stability is good, and the construction too

[FloggedSynapse]

Very good thread, this, useful. It will be a long time before I get a blue DPSS. Probably never will, actually, I think by the time I really want one, there might be derivatives of blue zinc-oxide diodes at longer than 405nm, with powers up to 100 mW. I live in hope, anyway. There is a LOT of commercial pressure to make them, so it will probably happen. Heading further off-topic, I can't help wondering, given that Nichia (Shuji Nakamura) invented some high-bright blue AND green LED's, why there are no green laser diodes.

Apparently it's quite difficult to create stable long lasting laser diodes with frequencies much higher than red. There are all sorts of LEDs available in colors throughout the visible spectrum, but laser diodes currently are only available on either end of the visible spectrum. I'm not certain what the difficulties are, but apparently the concentrated EM fields in the 'quantum well' lead to short device lifetimes. Most of the 'blackart' and patent work with early LD's revolved around preventing COD and increasing poor lifespans.

For example Sony was working on creating green direct injection LDs in the 90's, but they were stymied by very short lifespans. The best they were able to get was about 100 hours. The LD lased at ~515 nm. See this link - over 10 years old now:
http://www.sony.net/SonyInfo/News/Pr...9601/96D-014E/
You can see the complexity of the diode.

Apparently they were unable to improve the lifespan. Nichia (Nakamura) was able to create the current lot of violet LDs, but not without many difficulties, and the big manufacturers are apparently still having problems ramping up production and creating reliable LDs.

Of course violet allows them to get smaller diffraction limited spot sizes to allow DVDs that can hold more. My fear is now the violet LDs are here the economic drivers for laser diodes in the heart of the visible spectrum will disappear and we may not see visible LD's outside of red and violet.

I've always liked LDs for conceptual reasons - small and relatively efficient, even if the beam quality isn't that good. At this point the only way to get colors in the heart of the visual spectrum is to use DPSS tech, which gives good beam quality, even if it's not nearly as efficient as using direct injection diodes to create the desired wavelength directly.

[The_Doctor]

That is one unholy sandwich they had to make of that, to get green! (And not the nicest green, either.) No wonder a DPSS looked like a less complex answer. Judging by the NECSEL, Direct SHG to get visible from IR might always be a favoured method unless someone gets lucky with a new discovery. One idea that I like (not sure if it's realistic though) is a tunable IR laser just one octave below the visible range of 400 to 800. If it could tune the octave from 1600 to 800 nm, it would be a very useful visible laser if SHG doubling methods can also handle that octave change. As the SHG should be intracavity, I suspect that this much tuning might not work, and trying it might upset lasing.