Beam shaping and collimation of the Nichia 445nm 1W Diode

(under prep).

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It seems that these diodes have the same data as the Nichia NDB7412 1W 445nm diode, except for the 5.6mm case; despite of that the kind of these diodes is not yet entirely clear, I denote these diodes tentatively by NDB7352.

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Collimators

Collimator % Power Beam Quality
Aixis 405 100 good
Aixis 445 wrong coat 85 good
Aixis 405-445 100 good
Lens-27 (red coat) 102 bad
Swisslas Asphere 115 very good
O-ring 405-445 105 good
G-405    

Best value for the money is the O-ring collimator.


Anamorphic prisms

I got a few good ones quite cheap, the data are as follows:

Material: K9 = BK7
Size:7.8×12×16
Wedge: 33° Coating:AR/AR
Surface Quality:60/40 Flatness:lambda/4
Coating AR/AR S1:AOI=0,AR440~450 coating S2:AOI=56,AR440~450

The coatings are optimal for the incidence angles at the predefined magnification, so little loss is expected. That is, the indicence at the straight face is zero degrees and the angled side is 56 degrees, which is the Brewster angle (since the faces are coated the polarization plays almost no role). In this case the magnification of the pair is given by 2n~3, where n=1.5 is the index of refraction of BK7.

I measured carefully the loss of the pair and at optimal adjustment it is indeed about 3% (when another magnification is chosen, by turning the prisms, then the losses grow with the angle).  Here a movie that shows the measurement:

 

Simulation:

Beam shaping: L1= Aixis 405nm collimator, L2=1000mm fl cylinder lens to correct astigmatism, anamorphic prism pair circularizes beam (simulation with Optica):

At 445nm it is important to avoid SF11 glass:

SF11 glass transmission (source Melles-Griot):

BK7 glass transmission (source CVI Melles-Griot):

 

 


Attempts to get the circularized beam through a spatial filter

Only if a large portion of the beam is thrown away, one can get a nice homogeneous illumination pattern. Probably it is more economical to split part of the beam off with a mirror with a sharp edge, before the spatial filter, in order to use the "wasted" part for the object beam in holography.

 


 

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Vers . 0.3-09/10