Welcome to Laser Pointer Forums - discuss green laser pointers, blue laser pointers, and all types of lasers



445nm diode glows after being turned off.

leukoplast

Member
Joined
Jan 7, 2007
Messages
368
Points
18
I just noticed this tonight. I was using my 445nm 65mW in pure darkness, and when I turned it off I happened to bring the now off laser past my hand and I noticed some light still coming out of the laser. At first I thought it was a reflection of the streetlights outside or something, but upon inspecting further the light was coming from the diode.

I immediately removed the batteries and yet the light was still coming out.


I tried to take a picture of this. This is as good as I can get it with my point-and-shoot cam. Just to clarify, there is no power going to the diode whatsoever.

445diode-glow.jpg



Seems something in the diode is fluorescing, looks like some kind of GITD material. I guess this is how the laser creates the color it does?


I tried searching to see if anybody else mentioned this, but found nothing. So I am sorry if this is already known by everybody. But I found it rather interesting. :)
 



aXit

New member
Joined
Sep 15, 2009
Messages
206
Points
0
I have had this in a few of my builds, it goes away after awhile, doesn't it?

It's just some leftover charge in the capacitors.
 

leukoplast

Member
Joined
Jan 7, 2007
Messages
368
Points
18
My 405nm build doesn't do this, and it's using the same driver.

And yes it eventually goes away, much like how GITD material would eventually fade.
 

Benm

Well-known member
Joined
Aug 16, 2007
Messages
8,113
Points
113
Thats odd :)

Perhaps its not noticeable on the 405 because it looks so much dimmer per mW?

I don't know how long this glow lasts, but if its long enough you could try to short circuit the diode and see if it stops - thats one way to make sure its not coming from driver capacitors or anything like that.
 

Toke

New member
Joined
Jul 25, 2010
Messages
1,109
Points
0
I have a LED doing that on my test booster circuit, it disappears when I short the capacitor on the output side.
 

ElektroFreak

New member
Joined
Nov 7, 2008
Messages
5,727
Points
0
I was waiting for someone to mention this.. I noticed it a long time ago but I thought perhaps it was capacitors discharging.
 

JLSE

1
Joined
Dec 13, 2007
Messages
3,580
Points
0
Id imagine the output cap as well. The caps on the drivers I use
hold a charge for 15min post shut off. A PHR will remain 'glowing'
for 30 sec's or so.
 

lasersbee

Well-known member
Joined
Sep 20, 2008
Messages
17,680
Points
113
Yeah... I agree... It is most likely the Caps on the Driver
that are holding a small charge..
It is easy to check.... While ESD protected... short out
the driver out put and see if the glow is still there.

If not it is caps... if yes.. then it is the LD itself...

Jerry
 

ElektroFreak

New member
Joined
Nov 7, 2008
Messages
5,727
Points
0
I did a brief check and I noticed that a LOC diode connected to the same driver that I had the 445nm diode connected to does not do this. Hmmmmm......:thinking:
 

JLSE

1
Joined
Dec 13, 2007
Messages
3,580
Points
0
I have only noticed this in 405-445nm LD's, perhaps they are more
sensitive at really low current, and the 650's are not?

PBD should have a better idea on this one...
 




Top