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Laser Diode Data Sheets ?

S

Steve Kavanagh

Jan 1, 1970
0
Can anyone direct me to a data sheet for the type of laser diode (or
laser diode module) used in the really cheap laser pointers (the ones
with < 1 mW output, no fancy current regulator or power output
feedback...just a series current limiting resistor) ? My search
efforts have not managed to find one.

Steve
 
J

John Larkin

Jan 1, 1970
0
Can anyone direct me to a data sheet for the type of laser diode (or
laser diode module) used in the really cheap laser pointers (the ones
with < 1 mW output, no fancy current regulator or power output
feedback...just a series current limiting resistor) ? My search
efforts have not managed to find one.

Steve

You might try Lasermate, motto "The Friend of Laser."

John
 
S

Steve Kavanagh

Jan 1, 1970
0
Thanks, John. I wasn't aware of that company....but still, as far as I
can tell, their lowest power diode is 5 mW and their modules all use
feedback power control.

Steve
 
F

Fred Bloggs

Jan 1, 1970
0
Can anyone direct me to a data sheet for the type of laser diode (or
laser diode module) used in the really cheap laser pointers (the ones
with < 1 mW output, no fancy current regulator or power output
feedback...just a series current limiting resistor) ?

I direct you to this:
http://www.photonic-products.com/products/laserdiodes_visible/sanyo_visible_ds/dl-3148-025.pdf
My search
efforts have not managed to find one.

Hmmm- hopefully your application skills are better...if the output
monitor scares you, then maybe you should take up stamp collecting or
something.
 
S

Steve Kavanagh

Jan 1, 1970
0
Fred said:

Yes, I have found many like this...but the type of module I am asking
about does not use the power monitor for feedback.
Hmmm- hopefully your application skills are better...if the output
monitor scares you, then maybe you should take up stamp collecting or something.

Actually it is more the lack of the use of the output monitor that
scares me ! I am trying to understand how the manufacturers of such
laser pointers get away with it, what the temperature constraints might
be, etc.

It has just occurred to me that the cheap pointers may just be LABELLED
as "< 1 mW" for the purpose of fooling customers and customs inspectors
but may actually contain 5 mW diodes running at some unknown power that
may or may not be under a milliwatt depending on temperature, state of
batteries, etc. If this is the case then perhaps a typical 5 mW diode
data sheet could be instructive.

Steve
 
J

John Larkin

Jan 1, 1970
0
Thanks, John. I wasn't aware of that company....but still, as far as I
can tell, their lowest power diode is 5 mW and their modules all use
feedback power control.

Steve

Give them a call. They can usually find what you need.

John
 
J

John Larkin

Jan 1, 1970
0
Yes, I have found many like this...but the type of module I am asking
about does not use the power monitor for feedback.


Actually it is more the lack of the use of the output monitor that
scares me ! I am trying to understand how the manufacturers of such
laser pointers get away with it, what the temperature constraints might
be, etc.

We use VCSEL lasers, about 1 mW fiber-coupled, with constant-current
drive, and they work fine. We switch them on/off in a few hundred
picoseconds, and leave them on/off for indefinite times, so feedback
isn't feasible for us.

John
 
J

John Devereux

Jan 1, 1970
0
John Larkin said:
We use VCSEL lasers, about 1 mW fiber-coupled, with constant-current
drive, and they work fine. We switch them on/off in a few hundred
picoseconds, and leave them on/off for indefinite times, so feedback
isn't feasible for us.

You can do this because with VCSELs the threshold current tends to be
a much smaller fraction of the operating current. With visible laser
diodes (VLDs) this is not generally the case. E.g. the threshold at
25'C might be 20mA, with 30mA destroying the device. But the threshold
at 70'C might be 50mA...
 
J

John Larkin

Jan 1, 1970
0
You can do this because with VCSELs the threshold current tends to be
a much smaller fraction of the operating current. With visible laser
diodes (VLDs) this is not generally the case. E.g. the threshold at
25'C might be 20mA, with 30mA destroying the device. But the threshold
at 70'C might be 50mA...


Do the cheap laser pointers use photodiode feedback? They seem to work
fine.

John
 
J

John Devereux

Jan 1, 1970
0
John Larkin said:
Do the cheap laser pointers use photodiode feedback? They seem to work
fine.

Apparently not, according to Steve.

The VLD's I have used increase the threshold current with
temperature. So if you set the current to give the nominal output at
20'C, then they would just get dim or go out at high temperatures (or
as they self-heat). But if it got too cold, then you might be in
trouble!
 
S

Steve Kavanagh

Jan 1, 1970
0
John said:
Apparently not, according to Steve.

The VLD's I have used increase the threshold current with
temperature. So if you set the current to give the nominal output at
20'C, then they would just get dim or go out at high temperatures (or
as they self-heat). But if it got too cold, then you might be in
trouble!

One model (which I acquired for the princely sum of CDN $1.95) consists
of just three 1.5V cells, a switch, a 68 ohm resistor and a laser diode
(all in series of course), as far as I can tell. I have wondered about
holding in my hand for a few minutes and seeing if it goes out and then
leaving it outside for an hour and seeing if it goes out....permanently
! Or has someone in China figured out how to make a
less-temperature-sensitive diode ?

Steve
 
S

Steve Kavanagh

Jan 1, 1970
0
John said:
Apparently not, according to Steve.

The VLD's I have used increase the threshold current with
temperature. So if you set the current to give the nominal output at
20'C, then they would just get dim or go out at high temperatures (or
as they self-heat). But if it got too cold, then you might be in
trouble!

One model (which I acquired for the princely sum of CDN $1.95) consists
of just three 1.5V cells, a switch, a 68 ohm resistor and a laser diode
(all in series of course), as far as I can tell. I have wondered about
holding in my hand for a few minutes and seeing if it goes out and then
leaving it outside for an hour and seeing if it goes out....permanently
! Or has someone in China figured out how to make a
less-temperature-sensitive diode ?

Steve
 
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