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



445LD with Anamorphic Prisms on a Jayrob DIY

CDBEAM777

Well-known member
Joined
Feb 25, 2010
Messages
1,615
Points
113
I have been working on several laser related projects lately and this is one of them. Here are a few pics of my 445nm optical experiments. I decided to trial Anamorphic prisms riding on the front end of a Jayrob 532 DIY with a microboost driver set to max, a copper heat sink and the 445 lens from LarryDFW. I had a set of these prisms I was experimenting with in 2000. They are from Frontier Optics. I do not know if they are BK7 or SF11 material. They are not coated for 445nm.
Transmission losses are as expected…around 20%. With no prisms: 1110 mW …with prisms: 868mW. Beam is corrected somewhat. At 10’ with no prisms: 5.5mm x 1.25mm. With prisms: 4mm x 1.25mm.
The small set of Anamorphic prisms are positioned within 2 pcs acrylic flat stock at 31.2mm square...same size upper and lower...three flat head bolts are used to clamp the prisms in position. The result is an " Anamorphic Sandwich Assembly "...or ASA.
I was very lucky because the prisms are 11.77mm tall….which is just the same diameter of the Larry DFW focus ring. The ASA fits very snug on the OD of the focus ring. The final acrylic shroud/tube was added to protect the assembly…and for effect.
I experimented with many set angles for the prism set. There is a free program you can down load (Mathematica Player 7) which runs a virtual Anamorphic Prism set-up application. Very interesting. I still am not sure I have the best position???...I do have the maximum mW output for this set of prisms. It is known that the prism material should be BK7 and coated for minimum losses. I do not know what these prisms are made from…likely SF11 glass which has more transmission loss than BK7 glass.
The main purpose of this project was to show that additional beam shaping optics can be adapted for pointer use.
In conclusion…the use of prisms does somewhat lessen the fast axis divergence of the 445LD…but at a substantial loss of mW output…at least for the set of prisms I have. I have been informed by one overseas optics company that a specific coating for 445nm will decrease the transmission losses down to approx 15% and improved transmission will occur with BK7 glass vs. SF11. The use of anamorphic prisms may be acceptable if losses could be reduced to 10% or lower. Dr Lava is currently working on a Lab style set-up for the 445LD which will use TEC for thermal management and Cylindrical lenses to beam shape the output. No details are currently available but his optics choice MAY deliver less loss( less than 5% ).

CDBEAM
 

Attachments

Last edited:



daguin

New member
Joined
Mar 29, 2008
Messages
16,574
Points
0
Did you try rotating the laser. Polarity can make a difference in the output

Peace,
dave
 

CDBEAM777

Well-known member
Joined
Feb 25, 2010
Messages
1,615
Points
113
No...I will have to try rotation to see if that has impact on mW or beam dimensions...thanx !
 

lasersbee

Well-known member
Joined
Sep 20, 2008
Messages
17,708
Points
113
Nice Build CDBEAM777...

I heard drlava has a lens setup that will make under 1mrad
of divergence.... I may be wrong... and I don't know how
big his lens system is....

Jerry
 

CrazyMonkey

New member
Joined
Jun 13, 2010
Messages
102
Points
0
So, you went from 1.8mrad to 1.31mrad.
That's still a good improvement!
Have you tried changing the magnification?
You may already know, but ill mention just in case.
By adjusting the angle they face the laser and each other
you can modify the magnification. More power loss though.

Good stuff!
 

Morgan

New member
Joined
Feb 5, 2009
Messages
2,178
Points
0
There is a GB currently being done over at PL for a calculated prism pair.

I have a question though. Isn't the prism furthest from the output the wrong way round? I thought they presented the narrow end to narrow end when using anamorphic sets?

I am prepared to be corrected, as ever.

M
:)
 

climbak

New member
Joined
Apr 14, 2008
Messages
373
Points
0
not sure on that particular pair, but I looked on the thorlabs prism pair and it looks like the input side prism is backwards actually
 

CDBEAM777

Well-known member
Joined
Feb 25, 2010
Messages
1,615
Points
113
Dave...by rotating the LD...the Fast axis can be presented to the prism pair at any degree...I assume that if I am attempting to decrease the Fast axis divergence... this axis should be parallel to the prism top and bottom, and by doing so...the beam profile is made as square as possible.

CM...by magnification I assume you mean divergence...yes, adjustment of the first prism does effect divergence.

LB....Yes....how good will the Dr.Lava optics be??...how much will they cost? and can they be had in a reasonable size ???

Morgan...No...everything I have looked at has the small ends of the prism pair at opposite ends. I think I got that right ????

I am by no means anything more than a hobbyist. I know less about optics than I do electronics. I read, learn and experiment until I understand and am constantly humbled at how much I still do not know ...yet
For example...What is this Brewsters Angle ???
Did he play pool ??? haha...there is SO much to learn....have fun....and be very careful !!!
1W is da Schiz.....and should be GREATLY respected ...CDBEAM
 
Last edited:

CDBEAM777

Well-known member
Joined
Feb 25, 2010
Messages
1,615
Points
113
Holy Shit Climbak....you are right....and another humbling experience really unfolds !!!!
I just reversed the orientation of the prism where the beam path enters the set....just like the Thor Labs website shows....WOW....now that is a huge improvement....the beam looks VERY round....very round indeed...THANK YOU !!! It just goes to show....that is what this site is all about...sharing the information, sharing the science.... and having a good and safe time in the process !!I will do measurments on divergence and mW tomorrow ( Although I do not expect the mW to change ??) !!! Now....on to purchase a small set of Anamorphic prisms made from BK7 glass and coated for 445nm to lower the transmission losses !!! Thanx again...and CDBEAM
 

climbak

New member
Joined
Apr 14, 2008
Messages
373
Points
0
if you want something coated for 445, which may be hard to find as a stock part, it might be worth getting a group together to get a coating run. Thin Film Labs is a company I have had things coated from before at work and they are insanely cheap. Depends on the coating of course and how many in the run, but I had some diode facets coated for me one time for a failed experiment and it was only $300 for the run plus $3 per diode. Granted this is really expensive for a hobbyist if you don't get enough people to drop the price, but as far as coating goes he is by far the cheapest I have heard of commercially.
 

CDBEAM777

Well-known member
Joined
Feb 25, 2010
Messages
1,615
Points
113
Further measurements taken with correct orientation of prisms:

1) No prisms=>Beam at 25.5mm x 3mm @ 7.5m distance
2) Prisms => Beam at 12.5mm x 3mm @ 7.5m distance

Possibly someone could convert to mrad...I have not yet taken the time learn that math.

After the inital correction to the prism orientation...I have not experimented with various incidence angles of how the beam hits the first prism. So...the optimal Brewster angle has not likely been acheived. The current set up is now likely " In the Ball Park " ....more adjustments will be attempted and only improvements to beam divergence will be reported.

As far as transmission loss....with this new set up...still very slightly above 20%

I questioned my China Optics company about the switch to BK7...they state:

SF11 is the optimal material to make this Anamorphic prism because the refractive index of SF11 is the best appropriate for this kind of prism. Usually, the transmission at appointed wavelength depends on the incidence of angle, refractive index and so on. If you want to maximize the transmission of 445nm, we will do AR coating at 445nm for you.

So...as far as this source....looks like that SF11 is the only option.
I am pleased with the results thus far. Thanx for your comments and help...CDBEAM
 

ReNNo

New member
Joined
Mar 27, 2009
Messages
589
Points
0
1) No prisms=>Beam at 25.5mm x 3mm @ 7.5m distance
2) Prisms => Beam at 12.5mm x 3mm @ 7.5m distance
1. 2.7333265263515005 mRad
2. 0.9999996666668668 mRad

This is divergence for fast axis if diameter at aperture is 5mm
 

CDBEAM777

Well-known member
Joined
Feb 25, 2010
Messages
1,615
Points
113
Thanx Jerry...No need to re-invent the wheel eh??...and thanx to P137...so much good information !!!... I am modifing the ASA unit with 3 pcs of additional black matt finish acrylic to mask the small amount of side spill and provide a more secure coupling to the focus ring perimeter. Will post a few pics when complete. I am looking for a set of Anamorphic prisims coated to maximize transmission at the 445 line...preferable a small set. I want to determine what will be the minimum loss with prisms with the optimal characteristics. Thanx again...CDBEAM
 

RDTech

Active member
Joined
Apr 6, 2010
Messages
263
Points
28
I witnessed personally, ans assisted at laser trade shows a company named BlueSky Research in Northern California doing something new for that time, early '90's. They removed the LD can and mounted a small cylinder lens right over the laser facet, thereby slowing down the fast axis of most common 9mm visible laser diodes. It does seem, that like bar lasers, a cylinder lens would be most appropriate? Am I correct? Certainly nice BK7 coated glass would cut down losses. Edmund Scientific has a very large selection of cylinder lenses... This may not be a cure all, but should help. Not cutting the LD's open, using a small cylinder right after the diode before the lens??

Just a thought
 




Top