Prisms for 445nm diode front surface knife edging

[Solarfire]

Will ask the factory for the transmission curve. But as I remember the transmission is >95% and the reflection is <0,5%.

@Solarfire

Did you receive the prisms?

Don't know, I'm not at home yet...

[lasertack]

Here is the transmittance curve of the PBS. This curve shows the broad band coating 445-700nm. The transmission is >90%. For narrower bandwidth, let me say 440-490nm you can get >95%. For red diodes the transmission will be >95% as well, if 600-700nm coating has been chosen.

[Solarfire]

Will ask the factory for the transmission curve. But as I remember the transmission is >95% and the reflection is <0,5%.

@Solarfire

Did you receive the prisms?

Picked up the prisms at the post office today, might get to testing them later today.

[planters]

lasertack,

Don't worry, I'm not going to ask you to examine some other esoteric feature of these prisms. Rather, I am impressed with your laser profile images of the 445 beams. After studying them to see how to best set up for combining beams I noticed how rapidly the power drops; off axis. Is the scale linear in all three axises? Did you crop the "wings" that flank the long axis? What collimator lens were you using? Do the numbers represent a real life measurement such as mm?

[lasertack]

lasertack,

Don't worry, I'm not going to ask you to examine some other esoteric feature of these prisms. Rather, I am impressed with your laser profile images of the 445 beams. After studying them to see how to best set up for combining beams I noticed how rapidly the power drops; off axis. Is the scale linear in all three axises? Did you crop the "wings" that flank the long axis? What collimator lens were you using? Do the numbers represent a real life measurement such as mm?

What do you mean with "...how rapidly the power drops"? The second picture shows only a half of the beam.
The scale is linear. I used the aspheric collimator to get the whole beam into the beam profiler. The numbers you can see are scaled in um. The beam diameter which was reflected by the prisms was approx. 1x2mm. Or did I misunderstood your question (Did you crop the "wings" that flank the long axis? What collimator lens were you using?).

Alex

[planters]

Sorry, I will clarify. On post #48 you presented 4 images. The first two are only demonstrating the profile of the 445 beam and the prism is not, as I understand it, modifying the properties of the beam other than redirecting it. I am assuming that a nearly identical set of images would have been produced if the diode's beam was sent directly to the profiler. I am interested in the inherent properties of the collimnated beam. The images are revealing and quantifying important characteristics of the beam that I had been little aware of previously.

I am currently using the O-like lens and this lens produces a large central stripe flanked on either side by a much dimmer stripe. I had assumed that this was a property of the diode and that all collimators produced a similar feature despite variations in the shape/size of the primary beam. Maybe I am wrong and the collimator you were using does not produce these side lobes and so there was nothing to crop. No?

So, if scaled in um, then your image is produced at focus and is not a slice through the collimated 1 x 2 mm beam?

The power drop I am referencing is the intensity profile of the spot produced by the collimator and not any effect of the prism.

The purpose of these questions is to determine when knife edging these 445nm beams in there collimnated state, how aggressively they can be cropped/trimmed/shadowed by optics for maximum compression in both the vertical and horizontal axises and at what cost in terms of power loss.

Oops. Thousands of um means you were sampling the colimnated beam and not at a focus. Silly me.

[chad]

Just to make things more confusing.... Those diodes change their shape a LOT depending on power. What I would like to see is a profile at 1W 1.25w 1.5w with the o like lens. the other question is how far from the detector is the diode and at what distance is the lens focused at. Also, alex, is their a graph that explains the color regions? In other words what density do the colors represent. I noticed one of your pics there was an ellipse that represented the beam profile at some power level. could you do that with the o- like at max power?

I am jealous! That is a really nice tool, I wish I had one.

Oh and by the way, when you show a 3d view see if the software will let you do an isometric view.

chad

[planters]

chad,
You don't need one. Just be REAL nice to Alex.

[lasertack]

@Chad

Hi,

if you want one, just call Thorlabs and spend approx 4000 USD *hehe*

Ok, get back to serious things of life. I´ll make a complete measurement report, showing all parameters beam profiler can measure. Please forget all results and graphics I did before, because I measured several times with different diodes and it confuses a bit.
Please keep in mind that every diode has a little bit different profile and it will be changed while changing the current and temperature. Furthermore, the beam profiler can measure beams up to 4mm only. There is an option for estimating data (only beam size and ellipticity), what means that it estimates beam parameters if the beam is too large. O-Like´s produces >4mm beams. So this data will be only a reconstruction. The precision is around 90%. So please keep it in mind. I´ll measure both O-Likes and aspheric lenses.
It will be a nice saturday afternoon job
Will get back soon

[lasertack]

I´m back. Attached are the files and measurement reports for both aspheric and O´Like lens. For O-Like´s with the prisms I did not made a measurement report, because it was the same date as without prism. The reason is, that the beam size is estimated only.
I hope the pictures will help to make some things clear. The measurement was done with 1,1W output power with aspheric lens. The power with O-Like was about 880mW.
BTW I collimate my modules with a shearing interferometer. It is better for my eyes and more precise LINK









@Chad

Unfortunately the Thorlabs software doesnt offer the option of isometric view.

@planters

All of the O-Like´s produces "several" stripes, the bright and most powerful in the middle and one or two to the left and to the right of the bright stripe.