Engrave with which side of diode

I am currently investigating how my diode laser works.
Its a true fact that the shape of the beam is rectangular.
My question to the other diode laser guys. Which side do you take for engraving, the thick or the thin side of the diode?


The shape of the focus point varies with the laser in question.
For example on xTool D1 20w Pro (4*5.5W combined beam) it’s somewhat ellipsoidal oblong with ~0.04&0.05mm semi-minor and semi-major axis (0.08&0.1mm dia.).
On the xTool 2W IR head the focus point is round ~0.03mm dia…

I haven’t done any tiny detail engraving with the 455nm head that would benefit particularily either way, so I haven’t given it another thought.
Perhaps in the future I have to, one never knows whhat the future may bring :thinking:
On the 1064nm head the direction obviously doesn’t matter.


This isn’t the same type of diode optics and lenses?

Of course a different frequency… but doesn’t it produce a rectangular do also?



I haven’t taken either of the heads completely apart -at least no yet :thinking: - so I can’t be absolutely sure, but based on my limited knowledge of diode lasers and monochromatic optics I’m tempted to say that they are quite different.

Generally, in any kind of led the semiconductor materials and coatings determine the wavelength of the emission, so those two (455um &1064nm) can actually be very different in all sort of ways.
The abysmal efficiency of the IR led compared even with the poor efficiency of the “blue” led easily leads to the conclusion that they also probably are indeed very different.

Since the IR focus dot is round and somewhat small in diameter, I also assume that there’s only one led.
On the 20W 455nm head there’s four diodes, and the ineffiencies of the multiple mirrors and optics cause the dot to be oval in shape, and ~9 times the area of the IR dot.

I did open up the IR head mounting plate and obviously took a peek under the pcb when I modified the head for the adjustable focus arm, and there was only one component on the body that resembled something that could be a laser led, but since I haven’t opened up the “blue” head, I can’t be certain if there’s 4 of them or if the leds are actually located deeper inside the heatsink structure.

The time will tell though, sooner or later -hopefully later- the “blue” head will give up the ghost (or The Fart Of Lucas as the Brit bikers lovingly call it) and it’s the time to do some exploratory surgery :grinning: .


I can’t find anywhere that it is round from a solid state device…

My limited use of led lasers associated with lots of time behind a lens with various types of equipment, I’ve always associated the produced dot from the emitter part of the led, which is generally rectangular or square.

I don’t know of any produced led that the emitter is round. It wouldn’t surprise me, but it would waste more material during manufacturing… which would suggest rectangular or square would be a typical choice.

After a proper focus the resultant dot, is based on the source, which is rectangular, would also be rectangular…

With a shorter wavelength, a smaller dot should be possible.

I can find nothing, documentation wise, that seems to indicate what the dot size is or it’s dimensions for these uv diode lasers…

Conversely, my fiber, is led pumped… it produces a circular dot…

Mostly academic, I’m not going to cough up the $1500 for a uv led… the interest is still there.