shape of the spot?

[khurrle]

I apologize if this is in print somewhere I browsed for a few pages but was not able to find anything that really answered.

I saw in the 445 section that they will always produce a oval or line and not a circular dot.

Is this the case with a 405 as well? I notice that my 50mW throws an oblong spot and not a nice round dot. It doesn't bother me but I just wonder if it is the way that its supposed to work.

Thanks in advance.

 

[Lase]

A 445 is a multimode diode and produces 'lines' rather than a round 'dot'.

A 405 however is single mode and should produce a nice round 'dot'.

Have you got the laser unfocused?

Lase

 

[ElektroFreak]

There are always lots of tradeoffs in technology.. singlemode diodes like your 50mW 405nm have fairly good beam quality (still not perfectly round as you noticed) and can be made to run single-longitudinal-mode as well so they can even be used for things like holography, but in order to get much more than a few hundred mW out of semiconductor lasers you need to go multimode as the extra transverse modes pack extra power.

Multimode lasers are like having multiple singlemode lasers grouped together, but this results in poor quality beam compared to singlemode lasers, like the line you see with the 445nm diodes..

 

[Flaminpyro]

Dose the oblong change as you focus the lens ? is the laser focus-able ?

If the shape changes when you change the focus then you need to clean your lens, if it dose not change then it is the diode, it could be some contaminants on the diode window and you should be able to clean this or maybe the laser die it's self in which case you can do nothing about it.

 

[khurrle]

Yeah, the beam on this particular laser is oblong and not the perfectly circular dot. It is not focusable. It's just a 5.00 eBay violet pen so I don't expect an amazing laser. I was really just wondering if this was to be expected.

 

[ElektroFreak]

Totally normal.. you won't get better in terms of roundness with a diode laser pointer.