A plea to users of coated optics (G1 and G2) lenses

JLSE · May 2, 2012

Seoul_lasers said:
Didn't understand your question.
No they (laser diodes) aren't AR coated at all

How do you figure that? The facet window on every diode I have
ever handled, have a coating..

I always can identify random diodes just by the reflection. The same
shades you see on glass lenses, you see on the diode.. Or am I still missing something?

TomD · May 2, 2012

I need to ask, do all G1 and G2 lenses come from only one manufacturer?

I found one resource (L66) stating that they're made in the USA... but with the G2 lens having an "A" coat while the G1 has the "MgF2" coat. :thinking:

FWIW I tried this with a 405-G1 with a 2.3W 445 behind it: Focused at 4 feet into a cream-painted wall until it produced a sharp line "dot" using safety glasses, I took note of the visible splash (without the glasses), and it's approximately 14" in diameter.

S_L can you explain how they'd be "toast" and "throwaway?" They're not exactly being used to project images.

DTR · May 2, 2012

JLSE said:
I always can identify random diodes just by the reflection. The same
shades you see on glass lenses, you see on the diode.. Or am I still missing something?

Yep I do the same when I can't figure out what diode I have. They are definitely AR coated.

JLSE · May 2, 2012

DTR said:
Yep I do the same when I can't figure out what diode I have. They are definitely AR coated.

Thought I was losing my mind :thinking:

For the longest time, I also used this very example when a new member
wants to know which LD is which in a dvd sled..

Granted they are both canned diodes (650 & 780), the red will be a darker blue
coating.. Its an easy way to identify without powering up dangerous ir..

Seoul_lasers · May 2, 2012

JLSE said:
How do you figure that? The facet window on every diode I have
ever handled, have a coating..

I always can identify random diodes just by the reflection. The same
shades you see on glass lenses, you see on the diode.. Or am I still missing something?

Well from what I have been told, correct me if I am wrong,
the tinting on the diode window is used to aid in transmission of
the given spectra. Not specfically AR but an aid. All after optics should have coating to prevent a reflection.back into the laser cavity.

JLSE · May 2, 2012

Seoul_lasers said:
Well from what I have been told, correct me if I am wrong,
the tinting on the diode window is used to aid in transmission of
the given spectra. Not AR but an aid. All after optics should have coating to prevent a reflection.back into the laser cavity.

Im no expert on the subject, just shooting from the hip here.. But isnt that the
point of 'anti reflective'? My take was that it allows more to pass by limiting
the reflection.. :anyone:

AFAIK, you dont want reflection going back in, thats what the mirrors
at each end of the diode's chip are for, but for gain..

Seoul_lasers · May 2, 2012

JLSE said:
Im no expert on the subject, just shooting from the hip here.. But isnt that the
point of 'anti reflective'? My take was that it allows more to pass by limiting
the reflection.. :anyone:

AFAIK, you dont want reflection going back in, thats what the mirrors
at each end of the diode is for, but for gain..

Well, I concede here. There are diodes with AR coatings,
but they aren't going to have the same characteristics that our
coated optics will have. I don't know how well they reflect.
I think I will give OSRAM a call.

update;
called OSRAM Korea DIV. I'll hear back tomorrow regarding diode windows , coatings and coating materials.
Any additional information will be posted here. Lady I talked to is sending my question to their manufacturing div in China.
Could be some interest....

JLSE · May 2, 2012

Seoul_lasers said:
Well, I concede here. There are diodes with AR coatings,
but they aren't going to have the same characteristics that our
coated optics will have. I don't know how well they reflect.
I think I will give OSRAM a call.

I would think that they are not designed to reflect at all.. I don't think the windows are in
place to extend the cavity, which is what you may have with reflection, and no offset
angle on the window.

My logic tells me that the coating is in place to offer the least impedance
while the glass protects and seals the diode via the 'can'.

I also see lenses this way, where you want the least resistance for the light to enter
and be shaped . For each surface the light has to enter, pass, and exit, you
inherently have loss. The coating to my understanding is to minimize loss
and not interfere with the operation of the gain medium. Or at least be kept to a minimum.

Do post if you get some info on the topic..

op:

bweasel78 · May 2, 2012

Some diode windows are coated arent they? 405 diodes that iv had are very noticably coated. It looks like it could be to stop light bouncing back into the diode? i could be completly wrong about the purpose of the coating but its definatly there... its like an oily sheen yellow colour... couldnt find a bare 405 diode, but you can see it just fine on this one in a module...Look, thats definately coated isnt it. PS. when i started this reply no-one had responded to "diode windows are not coated", by the time id rummaged about to find the diode and take phote etc, i was well behind in the conversation... sorry people

Seoul_lasers · May 2, 2012

bweasel78 said:
Some diode windows are coated arent they? 405 diodes that iv had are very noticably coated. It looks like it could be to stop light bouncing back into the diode? i could be completly wrong about the purpose of the coating but its definatly there... its like an oily sheen yellow colour... couldnt find a bare 405 diode, but you can see it just fine on this one in a module...Look, thats definately coated isnt it. PS. when i started this reply no-one had responded to "diode windows are not coated", by the time id rummaged about to find the diode and take phote etc, i was well behind in the conversation... sorry people

actually we are far off the topic. the orginal post is out the secondary optic coating utilizing MgF2. ... look in the more recent post.

regarding diodes...
We don't know to what degree the diode coating serves as
an ARfilter/transmission polarizer or if it does at all.. i wouldn't chance a 400 buck diode just because I thought the coating was good enough.

thanks.
i'll post my findings tomorrow.

daguin · May 2, 2012

Seoul_lasers said:
You can clean that dust off with a blast of compressed air or need be , with some methanol..
diode windows as far as I know are not coated.

BTW, Thanks for adding constructive comments to this thread T_J...

They appear to be AR coated

I do not know what the coating is, but I have never seen the pattern that this fungus causes

Plus, at least on the inside, it is surrounded with dry nitrogen

Peace,
dave

cmaricle · May 2, 2012

You are probably right! As AixiZ, we normally don't post here as we don't want to be perceived as a company doing self promotion on the forums. But, hey, we are here if you have any questions and we really thank all our supporters on this forum. Chuck

Hiemal · May 2, 2012

I'm quite positive diode windows are AR coated.

There's no other reason for the color interference given off by the window; and they also match the same color given off by our AR coated lens anyway...

If they weren't AR coated then there would be much larger losses in the window...

Mohrenberg · May 3, 2012

If I lick a contaminated lens, will I get sick?

JLSE · May 3, 2012

Mohrenberg said:
If I lick a contaminated lens, will I get sick?

This is not the same as a Colorado River toad :tinfoil:

Blord · May 3, 2012

Your mouth has probably more bacteria and fungus than a dirty lens.

A plea to users of coated optics (G1 and G2) lenses

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