Don't buy a laser from ebay. The 10 dollar ones? I bought two of them to evaluate, expecting them to be junk, and they were definitely that. I'm not disappointed at all, because at 10 dollars, the hosts are cheaper than buying an empty host kit. Now I have two of them for future projects.
I bought
this SD-301 a few weeks ago. As you can see it's a more expensive version of the 10 dollar ebay lasers. The quality is better by far.
I don't think it's really 200mW but I didn't expect it to outshine my Lazerer LZCS 100mW. (The LZCS is Lazerer's version of the 301/301.) Both the expander and collimating lens are glass, and the expander is AR coated. Not sure what wavelength, I would assume green. The reflection from the lens is a dark blue-violet. None of my other 301/303's have that, not even my Lazerer.
The laser has a very short mode hop on startup. If you diverge the beam out all the way, or remove the front end entirely, you can get a good look at it. When powered, it starts as a messy TEM01 with what looks like a faint TEM21 or 31 superimposed. It's interesting, they are rectangular modes. This hops to a clean TEM00 within half a second, less if the laser is warm from use. Over the next few seconds the TEM00 divergence increases very slightly and then stabilizes.
I have no idea if your laser will do something similar. It will probably mode-hop a bit or have some kind of output scatter that it shouldn't. I suspect that the DPSS modules are actually factory rejects (albeit, of an good-quality model in this case) that were meant for a projector or some sort of lab equipment. The initial mode hopping would probably make it useless for those, but is barely noticeable in a pointer.
On tight focus, I barely notice it at all. I have to look for it to notice it. All I see is that the brightness ramps to full in half a second or so, usually less. After that the brightness remains constant for as long as I've run it at this point.
For the price, I'm impressed with this laser. Since it is advertised as a 301, I expected it to be on par with my other green 301's. It's actually much better, on par with my Lazerer, and slightly more powerful. Maybe the extra power is due to the AR on the expander. Internally it's a 302 or 303, since their heatsinks separate parts whereas the 301's is part of the host. This is a good thing, because the 302 and 303 are easier to work on if needed.
Highly recommend a 301/303 for your first laser, as they're a lot of fun to point around. It also has a removable body segment that allows it to be powered by an 18650 or an RCR123A. A lot of members here consider the 301 to be junk, but I don't get the impression that this one is, as every component is visibly better than the ebay units I bought. I think what you get what you pay for and if you're willing to fork out a little extra you'll get a much better laser than you can find on ebay.
Also for the price I would hope that the quality is more or less consistent for these lasers. I think if you get one of these you'll be a lot less likely to be disappointed than if you bought an ebay laser, despite the difference in price. There was a minor shipping error but it was probably a random fluke, transposed digits in the zip code. If it hadn't happened the ship time would have been around 10 days, which is really good when you're buying from China.
So yeah, there is my in depth reasoning on why I think this is a good first laser that should be seen as 'inexpensive' rather than cheap. Let us know what you decide.
