Mitsubishi ML520G71...Red Holy Grail or Flashlight Fail ??

[kecked]

...............

[steve-o]

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So, anybody find a decent short FL collimating lens yet? I've got a 4mm FL Thorlabs geltech lens epoxied in an aixiz barrel (I had to drill out the glass , turned it back into sand lol) ..just waiting to hear if the cylindrical Lavalenses are the ones to buy .. ?

[badger1666]

steve o
The lava lens works for me would be nice to try some other cylinder lens,but don't have the time or money
At the mo.
What should be noted using the lava lens make sure what you put the lens on is dead flat, or you will get
A squiffy beam shape, as I found out, also note don't put the lens to close to the collimator around 30/40 mm is good.
Remember lava a lens is a 1axis telescope setup so closer to collimator smaller beam bigger divergence,ect ect
Dave also does a short FL lens which is what I am working with. best I have got so far is 4x4mm@1.1 mrad.
Other members are also quietly working on a Lens setup that may well be better,all will become clear soon enough

@ Andy any beam or power measurements yet??

[CDBEAM]

First...I want a new generation of Laser Diodes from the work currently being done at NRL...They are experimenting with... changing the shape of PbSe (lead selenide) nanostructures to enhances a down conversion process known as multiple exciton generation..."A need more power...Scottie " See Photonics Online ( Sorry...they do not permit links )

Secondly...See attached pic !!! Where to get M9 very short FL ( around 2... I think ) Collimation lenses ???

BEAM

[steve-o]

..suddenly I need a cookie .. no a lens.. definitely a cookie..uh - lenses.. lenses .. gotta stay focused here ..

Thanks Badger

-edit- @ beam - we were typing at the same time LOL at that pic :]

[LaNeK779]

I tried another way, contacting some optics companies, giving them the datasheet of the diode and describing what was needed.
The good people at http://www.doriclenses.com/ were kind enough to answer and let me share their replies with the forum.

so, the first way to deal with this could be (i quote their optics engineer directly)

Because of aspect ratio of 1x40, it won't be possible to circularize the beam in the near and far field. As far as we understand, you would prefer to equalize the far field (divergence). In that case you need 2 crossed cylindrical lens to collimate each axis separately with focal ratio of 1:40. to get 1.5 mrad divergence, you need relatively long focal; i.e. FAC lens with F = 0.9 mm and SAC lens with F=36 mm.
for the FAC lens, you need acylindrical or GRIN lens to remove spherical aberration; here are few choices;

Acylindrical FAC-0.900(L)
GRIN cylindrical lens DGI-1.500 (F=1.03mm)

for the SAC lens, cylindrical plano-convex lens will be fine;

CYL_PCX_BK7_F=36mm

But then you need to remove laser diode can to align the FAC lens close to emitter. Also, in the near field, beam will be quite elliptical; about 1 x 10 mm and will tend to equalize with propagation. But this 10 mm width in near field is maybe too large for your mirror. If so you have to make some compromise on divergence and use shorter focal or clip some beam power or use single mode emitter (if power is sufficient)

as they note, this implies decaning the diode, so it could be worth a try with the 500mw open can version (and big mirror galvos)

for a more down to earth approach, they gave me a second alternative, which is pretty much what all you people here have been trying. the interesting part is the zemax screen shot they sent me, analysing the beam profile and characteristics

Another possibility (if you prefer not to remove can and not use too small optics) is to use this 4 mm focal aspheric lens to collimate, and add a cylindrical telescope to increase slow axis beam size, then decrease its divergence by the same factor.

In order to reduce the actual 10 mrad in slow axis to something around 1.5 mrad, you need a cylindrical telescope with 7x magnification.
Lets say F1 = -4 mm and F2 = +30 mm.
See attached file.

Our suggestions and comments are given in order to help our customers select the right product for their application.
So it is okay if you want to share this information on forum.

Let us know what is prefered solution and we'll provide official quotation for selected lenses.

Jean-Luc

well, i am impressed with the software, to say the least. but then again, that is to be expected by pro-software

so, what do you guys make of this?


edit: try saving the picture and zooming in on it, to see additional details

[kiyoukan]

So what would the beam size and results be with the second method?
i saw it listed for the near field but the second one gets us 1.5mrad at what size near and far?
to think we do all this testing with optics and this is the first someone asked a professional.
The second beam profile does not look to bad. stack 4 on top and get a square beam of decent power.

[Solarfire]

I tried another way, contacting some optics companies, giving them the datasheet of the diode and describing what was needed.
The good people at http://www.doriclenses.com/ were kind enough to answer and let me share their replies with the forum.

so, the first way to deal with this could be (i quote their optics engineer directly)



as they note, this implies decaning the diode, so it could be worth a try with the 500mw open can version (and big mirror galvos)

for a more down to earth approach, they gave me a second alternative, which is pretty much what all you people here have been trying. the interesting part is the zemax screen shot they sent me, analysing the beam profile and characteristics






well, i am impressed with the software, to say the least. but then again, that is to be expected by pro-software

so, what do you guys make of this?

Like I said a long time ago, Optima and an 8x cylinder telescope. I still don't see how badger and andy are getting what they claim to be getting. A shortening of the fl always results with increased divergence unless the NA is too small and clips the beam.

[badger1666]

@ solarfire
well we are getting it, and so is one or two silent members getting the same , why i dont know, and with good power too.
guess these things happen somtime
the pics dont lie

[andyf97]

@ LaNeK779

Look at the profile bottom left of the screen shot and then look at my photo in this post.

http://www.photonlexicon.com/forums/...192#post210192

Pretty similar ey!

By the way did they give prices for these lenses?

There results are ok even with Zemax, but Badgers and my results strangely are better which prompted me a thought on the maths. there calculations are based on the emitter being 1x40um, can you ask them to do the Zemax again with 1x20um to see if they get a 50% difference.

By the way is it in any datasheet the emitter being 40um? I just took a look and can't find it referenced to be 40um. from the G71 I quote the emitter size being "A broad stripe structure " from the P73 I quote "A broad stripe structure ". No 40um there.

Lets see where this 40um comes from http://www.google.co.uk/#sclient=psy...w=1400&bih=858

Searched for a ML520G71+40um



We are also assuming something else, the test diodes don't come with any Mitsu packaging, are we sure they are Mitsu diodes in the first place because if zemax is right and if it was 40um stripe the diodes I am testing should have far worse specs than me and badger are getting..So something is not right here with the maths as they are based on speculated values that are not listed in any datasheet.

@ Badger, did you get official Mitsu diodes to test or one of the ones at 69USD?

It could be, these diodes we are testing with are simply not what we assume them to be...

@everyone else: I am not going out of my way and at my expense to prove something is right or wrong, If LaNeK779 and a few others don't agree with the results then why they don't do there own tests instead of going very far out of there way to try and prove the diode to be bad, what is this, they want the proof of the pudding to save them doing any work?? "Prove it works, then I will buy the diodes".