Fun & Educational Experiments

Hi all,

This is my first post on this forum, greetings all! I've been a casual reader of this forum for a while but have only recently started to seriously experiment with lasers. I'm a responsible adult in my late 20's who takes safety very seriously and I use all the appropriate precautions.

I have 5 lasers:

1 x 10mW 650nm red
2 x 10mW 532nm green
1 x 20mW 532nm green
1 x 30mW 532nm green

I am a keen astronomer so this was my main motivation for getting in to lasers, the 20mW and 30mW look awesome when used for star pointing - it's literally made finding nebulae, clusters, galaxies etc so easy.

The reason I write this post is that I am wondering if there are any other experienced experimenters out there that can suggest some further things to try out. I've done extensive experimenting with fluorescence, diffraction, refraction, diffusion, reflection, mirrors, beam splitting, photography, forensics etc.

I've had a lot of fun using diffraction gratings to get some great looking shapes and beam configurations, I've cannabalised many, many cd players and cdrom drives much to my wifes displeasure (I usually leave the leftovers scattered throughout my house) to get access to the dielectric mirrors, lenses and gratings.

I've found that using a dichroic mirror cannabalised from what appeared to be some theatrical lighting system is excellent for observing flourescence in objects illuminated by 532nm wavelength. I couldn't believe how many things fluoresce, the glass of scotch sitting in front of me fluoresces a very bright red when I shine my laser through it. The mirror appears to block out wavelength very close to the 532nm allowing me to observe induced light at other wavelengths.

I am curious though, as my recently purchased 30mW is a bit disappointing compared to my 20mW - in fact, the beam itself does not appear as bright from what I can tell (I don't have a laser power meter - this is next on my list), although they are very similar. In fact, the 30mW spot looks ever so slightly more yellow than the 20mW, I'm talking barely perceptable difference, but a difference none the less. The power output seems to fluctuate quite a lot more in the 30mW also.

Can anyone give me advice as to why this would be the case? Am I not warming up the laser enough? What are typical warm up times for these power outputs? Can the wavelength output vary slightly between lasers? Anything else that experienced laser experimenters can suggest? Is there a way to compare the power outputs without using a power meter?

Cheers guys, looking forward to your comments!

Hello uberdaz,

Can't really suggest any experiments you haven't done, as it seems like you've been quite thorough so far

With regards to wavelength variations/fluctuations, I do believe the infrared pump diode can shift very slightly in wavelength, depending on its temperature. Whether this will also cause a shift in the green wavelength, I don't know. Doubt it would be perceptible though, even if it did occur, as we're talking about very few nanometers any way.

I have a few green DPSS lasers myself, and all of them are very sensitive to temperature. They all start out low and then climb to reach a maximum in 1-2 minutes as they warm up (except for an 80mW mains powered lab style model w/big heatsink - it takes around 20 minutes to reach its maximum!).

If you haven't already, I'd try and let your 30mW be on for a minute to 1½, to see if it gets brighter. Without knowing the duty cycle of your lasers, I wouldn't recommend running them any longer without a pause to cool down.

Cheers,
Erling

Thanks Erling! Appreciate the advice.

I tried out warming it up for a lot longer, letting it rest every minute and a half or so as you advised and it's starting to look like it's matching it's rated output. I didn't realise they were so temperature sensitive - it's quite cold where I am so perhaps the ambient temperature is affecting the output.

In regards to experiments, I think I've done all I can with the crappy salvaged optics I have lying around, though I'd like to spend some money on some decent optical components, maybe try around with holography but it looks quite intricate - I usually don't have the patience!

I'd like to get in to amateur laser display systems, I've tried a quickly made dual mirror display system where you get the 'spirograph' looking shapes which looks real cool, but I've seen some people on the net who've made some awesome projections systems.

I'd like to ask, what are the typical uses for your lasers??

Cheers, Darren

Hello again Darren,

Temperature can have a profound influence diode lasers for sure, although some seem more sensitive than others. Take a look at this photo taken outside last year, on a hazy but cold (0 deg C) evening:



The upper green laser is a 25mW which seemed unperturbed by the cold. The bottom one however, is an 80mW, which was visibly weaker than the 25 mW. You can also see that the beam appears 'fractured' or 'split'; also a result of the cold. As soon as they were brought indoors again and got back to normal temperatures, the 80mW was again much brighter than the 25mW, as it usually is. Red one in the photo is a 100mW 650nm.

With regards to uses of my lasers, I must admit that I really don't have any practical applications for them. Could use them for starpointing, but even with a keen interest in astronomy, I very rarely find myself in position to point something in the sky out to others. Main reason for having them is an almost lifelong fascination with lasers. First book in English I ever tried reading - with great difficulty - was about lasers; provided on special order by the local library. Had to borrow a technical English dictionary too...

I've done the odd experiments, including cutting electrical tape or other forms of burning/melting suitable materials. Most time though has been devoted to photography, trying to get good beamshots and doing some setups with mirrors and prisms.

Like you I would also like to move into the display/lightshow field. Was in contact with someone from a company planning on supplying exactly the tools needed for this and other forms of experimentations for the laser hobbyists. He talked about letting me be a sort of 'guinea pig' on a basic beginner's kit, to test how easy it would be for the layman to get something useful out of it. It's been around ½ year since I last heard anything from him though, so I fear it has come to naught.

Cheers,
Erling