5 Diode Laser Myths That Just Won't Go Away

So much great information. Thanks Steve

Thank you for all the work you do.

Thank you so much for sharing these knowledge Steve, learn a lot from it

Thank you ! Very informative

Thanks Steve! You videos are explaining a lot.

Nice work Steve 👍😊

A great explanation. Thank you ☺

Great video, thanks 👍

thank you, terrific explanation.!

Hi Steve, this is a very good and interesting video. You have explained it very well. Only at your 4th myth, you are not wrong, but also not completely correct. If you shine the light of multiple lasers through several partially transparent mirrors, you will notice that the first laser (the top one in your diagram) experiences the least amount of loss. As you mentioned, this mirror is not partially transparent, so the loss is not significant at this point. However, what does come into play is that if it is a glass mirror, diffraction and loss of intensity occurs. I don't believe a glass mirror has been chosen here, but that doesn't matter for the rest of my explanation. The laser below it must shine through a partially transparent mirror because the light from the laser above it must pass through. To start with, there is some loss from the upper laser because glass, no matter how clear, converts light into heat and changes the intensity of the light. As long as we can see glass, it absorbs light intensity; it's as simple as that. Additionally, there's a problem where light enters the back of the glass at an angle and, due to diffraction, exits at a slightly shifted angle, which depends on the thickness of the glass used. The laser shining from the other side of this glass enters at a different angle and must pass through the glass surface twice – once towards the back of the glass where the foil or deposited metal is that reflects the light, and then back out at a 90-degree angle. So, there are two instances of diffraction and loss of intensity due to the brightness of the glass. By now, the beam of light has become broader, and this broader beam continues downward to the next laser. This effect repeats several times, and when you compare the differences between the first stacked lasers and the current generation, you'll see that there are significant variations in the amount of loss. It's not a standard 4% per glass piece, but the loss increases as you go through multiple layers of glass. This loss is partly due to the glass absorbing heat and thus, lowering intensity and partly due to diffraction, causing some of the emitted light to simply not reach the final lens. As technology has improved, laser developers have started using better diffraction gratings to minimize this loss in intensity instead of caring about optical focus. However, you'll only find this in very few consumer diode lasers because it's an expensive and difficult technique and is also sensitive to impacts. In the consumer laser diodes used in most of our laser engravers, much more attention is paid to the final lenses that focus the light into a usable beam than to the light path leading to the final lenses. As said, you are absolutely not wrong, but you can't say it's a 4 percent loss per element. Greetings, Brian.

thanks for sharing

You are without a doubt one of the smartest people I've come across on YouTube and certainly in this community. I'm pretty good at technical stuff but I don't know that much about lasers and how they work. Now I do. I have a little 5 W Hobby laser That I got as a birthday present. Definitely looking to upgrade in the very near future. My partner and I plan to do all custom engraving and we have a good contact for doing custom motorcycle and car parts (chrome accessories). You have helped make some of our buying decisions a whole lot easier. Thank you sir,you now have a new subscriber.

Steve for president!🗽

The biggest issue is prefocus collimation and integration of the optical power. The most efficient systems use FAC mucrolenses on the diodes, a series of knife edge mirrors and a polarized beam combiner followed with a collimation lens. Such syatems can give a final focal spot of 0.1 to 0.02 mm. Use the dodes to pumpa fiber optic and you can get down to 0.001mm. In essence the tradeoff is brute force power for a cleaner beam spot at your workpiece. ❤

Thanks for the info. I learned a lot. I especially appreciate the power and cutting depth info. I almost paid more money for a 48w laser that could be switched to 24wfor finer engraving. Sounds like that would have been a waste of money based on your info. Instead I opted for a 24w at half the price with a motorized x axis that can automatically step down for multiple passes on deeper cuts. Sounds like I made the best choice without knowing it. The cuts may take longer, but will still be possible and with a better kerf, and I won’t lose anything in fine engraving.

Very interesting... and useful information (I'll have to admit that I knew most of this already). I do, however, have a few suggestions for future tests that might give some interesting results. This test involved CUTTING... and of one specific material... 1. It might be interesting to see the results with different materials. One example is that I would expect less dense materials to require less power to cut - which is going to affect the kerf and the possible cutting depth. The power density in the beam is higher where the cone is narrower... Therefore we would expect to be able to cut "heat resistant" materials only at a distance close to the focal point... But we would expect to be able to cut softer materials, with less heat resistance, over a much larger depth range. (So, for a given power, and the same focal length, I would expect to be able to cut much thicker balsa wood than walnut, at the "expense" of a wider kerf.) 2. It would be interesting to see how multiple cuts affect the overall "capacity"... and how much you gain by repeated passes. (I assume that, due to focus depth, and potential build up of charcoal residue, you gain less depth with each repeated cut.) (I've also seen commentary about making multiple cuts... and advancing the focus lower with each one...) 3. It would be interesting to see the effect of air assist under various conditions. 4. This test involved cutting and presumably the ability to do clean cuts. HOWEVER, the situation will be different when it comes to ENGRAVING. For example, a finer beam is going to be able to engrave finer lines. 5. I've heard some people discuss the idea of deliberately de-focusing the beam to achieve "shading" on some materials. I suspect this would be largely impractical with the power of most diode LASERs... but an interesting thought. 6. I just ordered an XTools F1, which is galvanometer based... This means that the beam is directed in a different way... For example, with pictures I've seen of the LASER Pecker, it looks like the beam exits a relatively small lens, resulting in its hitting the surface at an angle when away from center. I've also seen videos of some fiber LASER engravers that seem to direct the beam from a VERY small lens aperture... I would expect this to result in an angled cut when cutting - with the cut at 90 degrees at the center and an angle that increases with distance from the center. (unlike gantry-type diode LASERs). I would also expect that this might not occur to the same degree with my new F1 (which looks like it has a larger lower lens). I have never heard this mentioned in a review... (I KNOW that the 10w LASER in my new F1 isn't going to be cutting 2x4's... But I do wonder if it will be adding a variable angle to cuts in thin plywood - UNLIKE a gantry-style LASER - or not.) Obviously I'm going to test some of this for myself when I get my new unit set up... But it seems like it all might make worthwhile content for a few test videos :)

Hi, Steve, just wanted to drop you a quick note to thank you for all the amazing videos you do! On another note (and somewhat off topic), I'm looking to purchase a 40w-50w CO2 laser in order to cut clear acrylic. Would you be able to make a recommendation of brand/type to buy? I would really appreciate it!

Thanks a lot Steve, just what i was asking for, it will sure help me decide on my next upgrade. Didn’t quite understand how it happens that between 5w and 33w the power intensity is only 4 times more, (less than i expected) while the speed is 10 times greater (more than i expected). Intuition buffling… At the end of the day whay i really care about is getting a faster time-saving machine, so i am pretty happy with the data. Still, i am curious why it is so.

Thanks for this video. I am considering purchasing a laser and this certainly answered a couple of questions that I have had in mind in trying to determine what would be the most useable for me. Economics become a central question: “If I spend more for a higher power laser, what benefit will that provide?” This video helps me understand. Good job.

This has certainly cleared up a few points. Just a point if a laser diode is being sold as a 10w laser is the energy output 10W? I say this as for example you often see vacuum cleaners for example at 1500w but that's energy consumption and not the actual power delivered to the motor.