WazUp? (Up = update)
Almost summer light rain...
That's what prevented me from capturing my artwork in progress. Stormy clouds, bit of lightnings and thunders. Hot and humid. We had 30 degrees Celsius today most of the day, after I returned home outside temperature was 19.6 around 9 pm. In the forest, where hot air is held by layers of dense leaves it was likely more. It was long continuos light rain, little to no wind. Therefore water from leaves managed to vaporise before becoming too heavy to fall on ground. This raised the temperature due to humidity what I guess was around 22-23 degrees.
There was even heavy rain during the night. Nothing healthy for my lasers, as it takes some time to package everything and in case of sudden heavy rain I could get at least some of them wet.
In "mild" climate and the fact, that 19th April was last snow here, this is somewhat wild. Crazy weeks, where all possible conditions (extept tornadoes and few other extremes here) were able to fit one day, I have no doubts saying that.
Artwork in progress
Extensive analysis of the best testshot has been done. Conclusion: Horrible. To be honest, in my beginings after receiving my 589 nm Yellowie it would be my best shot. Something awesome and from Laser Sun it would be the second best (but it would be close).
For example one of the errors was even my Sky Beauty (473 nm) switched to (near)TEM01 at the end of the exposure and creating therefore double beam. I wrapped it too much/ran it too long, so better cooling was needed. I'm still learning.
So... I'm working on the artwork further. I have several tips for better composition, correcting the errors and exposure times. It is much easier to use feeling with experience and science based assumptions instead of using stopwatch. There is too much stuff to handle fast and do the art. Anyway I often count time in my head, to have some reference.
DPSS instabilities experiment
As always I could not stay home and went in the forest on my bike. The above mentioned conditions seemed interesting to me to try what I observed earlier, I tested my Evo for mode hopping and tried to find some thermal instabilities of quite simple DPSS laser. I mean compared to more advanced lab lasers with ring cavity for example.
Note: I warmed up laser immediately after pulling it out, to ensure it is higher temperature than environment to prevent any moisture condensating. There was a slight power drop observed, about to the level it is not able to light cigarette (common from my experience). Usually at temperature of evironment around 25 degrees Celsius. Anyway the laser was not hot, just slightly warmer than usual, but nothing extreme. I used quite fresh Energizer Lithium AAs for powering it.
That was really nice experiment.
I loved it. This laser is extremely great for studying it. I read of course a lot of theory, but seeing this in real is something awesome.
Just see commented pics from mobile cam, sorry for quality, I just resized them to fit here better. I think they are sufficient for ilustration purposes.
Projection screen - a tree trunk. It was like 15-20 meters far from aperture I guess. Beam was collimated as coming out of laser. Slightly dirty protection cap (but just a few dust particles – nothing changing much the beam according to my experience – it is just not as clean dot as the coming from lens being protected) as this one used is heavy duty, I have another one for precise lasering with Evo.
(Near) TEM00 at full power. Usualy it is nice round TEM00, but the conditions and longer use make it out of optimum range.
It might be not noticeable much on the photo, but there was a thin line of slight decrease in intensity crossing the dot in the middle. Therefore it was not perfect Gaussian profile. I noticed it by a very close look at the dot and needed to reposition it to confirm and make sure it is not caused by structure of the trunk or someting else.
Lowest power - TEM01. It is usual for Evo to be stable at this mode on low power, but now I observed not only initial switch, but rapid switching instead. I observed it earlier under slightly different conditions. It looked like strobe mode, closer look on beam showed the truth. The frequency of switching was quite stable, around 4 Hz, I guess. Now I could not find settings, which would induce such a stable switching.
Sequence: TEM00 - near TEM00 -near TEM01 - TEM01 and back
I observed it even at somehow colder conditions and it was more TEM00 - TEM01, sometimes near TEM00 and near TEM01. Maybe video of it would be nice. Anyway this was first when I observed this effect, but on some mid power.
Some mid power - TEM02 transiting rapidly between TEM01 in various combinations. You can see also photo through glasses from my first observation when it was more stable at TEM02 earlier this month, here it was more stable. Also hard to capture as it was still changing. (The earlier pic is from much shorter distance and different tree was used.)
And finally something I’ve never seen before with EVO – TEM03! At some mid power, I cannot really distingush between mid power above used as they were really close.
Changing through some middle stages. At one moment it was stable for a few seconds, but swithed to rapid hopping. Definitely there were clear 4 beams leading from dots to the aperture! Before I managed to take the pic of clear dots, they started to switch through middle stages again, but this one shows it quite clearly. It might look similar to TEM02, but the switching had different characteristic. I also checked if there is nothing obstructing the beam of course.
And some not that underexposed photos for comparsion how it is seen – very bright.
TEM01 – You might notice interference patterns caused by two beams interfering.
TEM00 (near TEM00) – The dot is very bright. Anyway it was convenient to look at from side and a meter or so (no feeling of too bright light, no afterimage). The tree projection screen has quite low albedo and rough surface make the reflected light less concentrated and intense.
Those experiments are leading me to idea of cooling them - best candidate is using cooling bags (you put them in freezer to cool them) and silicagel in some wrap. I discussed it before on LPF. I also considered many options of cooling, but I’m looking for something simple, versatile, reliable and fitting my needs.
Instead of neoprene I came with beta test using black paper and wrap foil and silicagel close to module. There will be cooling bag used in some zip back with air inside to insulate it a bit and have some kind of temperature regulation according to how much air is closed in the sack and creating layer of variable thickness. And this cooling wrap will cover temperature sensitive parts of the laser. In some cases even batt comparrment. This tied together with black rubber string. This would be laser prepared for laserpainting in these conditions. Even thermometer is considered, for tests. One of the questions is the positions of holes for buttons.
Once this idea is developed I could consider doing some advanced (e.g. neoprene) version. Should be very versatile for my needs.
I hope you enjoyed this wazup.
