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Green emission from 445 laser diode

Benm

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Here are a couple of pictures, showing that the A140 445 nm diode produces some green lines when driven far below lasing threshold. The first picture is the laser running at ~5 mA, where you can see some greenish lines produced by the impurities in the diode.

The other pictures shows it at a bit more current, but still far below lasing threshold - the green is no longer perceptible.

This effect is similar to blue power leds producing often yellow light at very low voltages, but its very difficult to produce with these diodes, just a tad more current and the blue completely overwhelms the green lines - the semicondutive materials used in these diodes appear to be pretty pure.
 

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Benm

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They do, and it its more visible to the eye since the primary 405 nm laser line is so invisible on non-fluorescent surfaces. With blue leds and bluray lasers i've only observed yellow or orange stray emissions though... and these 445's have little or none of those, just a very visible line in the green.
 

mfo

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They do, and it its more visible to the eye since the primary 405 nm laser line is so invisible on non-fluorescent surfaces. With blue leds and bluray lasers i've only observed yellow or orange stray emissions though... and these 445's have little or none of those, just a very visible line in the green.
Maybe those impurities will pave the way for green diodes?
 

Benm

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I doubt it, these are not lasing transitions at all. To give you a clue, the picture of the green lines was taken at 5 mA or so, while the treshold for these diodes is well above 100 mA. It took a long exposure to produce this picture (10 seconds or so), although the green-cyan color of the stray emissions is much more visible to my eyes than to the camera used.

At even lower currents a yellow color can be seen when looking at the diode directly, byt could not capture that wihh my camera. At such minimal currents its safe to look into the diode directly as long as you have a stable driver - i dont recommentd trying it unless you are certain about that.
 




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