DTR's Laser Shop: Diodes-Drivers-Lenses-LEDs & More

[DTR]

Alright here is what I am seeing on the G71 VS P73. Seems to me a lot of the light on the P73 is not in the main spot like the G71. Maybe call it overflow.

[DTR]

Mitsubishi 500mW 638nm Laser Diode ML501P73

I know this diode has been around a while but never did do a testing post on it so here is one for reference.


Divergence

300mW ML520G71 VS 500mW ML501P73




G-2 67.98mm @ 25 Feet
Three Element Lens 36.32mm @ 25 Feet



Power test with a G-2 lens.

[slicklasers]

Looks like the mitsubishi wins over Oclaro, more watts per amps… I guess I won't be having to spend a lot of money changing out a bunch of diodes yet

[DTR]

Looks like the mitsubishi wins over Oclaro, more watts per amps… I guess I won't be having to spend a lot of money changing out a bunch of diodes yet

Yea I would not rush out to swap out your units but for new builders it may be a personal choice. If you are trying to stick to the datasheet recommended max 800mA on the Mitsu gets you 700mW but 1100mA on the Oclaro gets you 850mW.

[planters]

I disagree with you guys. This is my opinion, but the bigger problem with the red diodes (all of them) is beam quality and not power. Canned is, again in my opinion, a benefit as well. The P73 and the Oclaro both maximize at 1.4A. Any higher (at room temp) and the power output just plateaus and you are straining the diodes unnecessarily. The difference between the power output at that current is 1.2 vs 1.1 W and the Oclaro doesn't throw some of that into the wings.

DTR,

I have found that the beam quality difference between the P73 and the G71 is more pronounced than your image suggests. I have compared these two with Dave's 2mm and Optima's 4mm aspherics. The divergence you show with the G-2 is enormous in both the slow as well as the fast axises. With the G-2 you get 9 x 3 mrad and with the 3 element you get 4 x 1.5mrad. Few of us bother to correct the fast axis and so with these 2 lenses your uncorrected divergence is substantially higher than is typically seen. This is not a criticism. Rather, I think the practical beam quality needs to be evaluated some more before any conclusion is drawn.

[CDBEAM]

OK...I gotta throw in here...It has been over 18 months ago.....But...IIRC....I found that....practically speaking.....the farfield geometry of the P73 was equal to that of the G71....AFTER Cylinderical optics !!!.... I have no Beam analyzer at my disposal....just the typical FF measurement method.

I know the emitter size of the P73 is supposedly larger than the G71....BUT.....IF...IF the P73 is centerized to LSP's 2mm collimation lens....then....I saw no more aberration on the P73....than I did on the G71 !! Possibly the pivotal point here is that the P73 propagation must be spot on as it enters the 2mm lens. I know that the G71 should deliver less divergence....but...I did not see it !! I have used both the Adjustable LD mount from LSP and custom mounts of my own.

SOooo....IMNSHO....we need to compare the 63193 to the P73 !! Both in the arena of PO - Slope efficiency and FF geometry.....and I agree with Jordan....Too bad that simple A-prism correction cannot be employed !! Cylindericals are much more demanding to work with...but....can eventually be dialed in !!

CDBEAM=======>

[planters]

CD,

I have to disagree with you as well, much as it pains me. If I remember correctly, the emitters of the P73 and G71 were directly measured by a member with an EM and the G71's emitter was only 70% as wide as the P73. Similar far field performance WITH IDENTICAL NEAR FIELD DIMENSIONS does not make a lot of sense.

Cylinders are not hard to dial in (the centration re the collimator is) and if the near field is measured as well as the far field then a pretty good estimate of divergence can be made. Using the 4mm lens from Optima makes the measurements and ratios easier, but they are not difficult.

At room temp, it looks to me as if Jordan's measurements show similar output for these two diodes up to about 1.4A where they both seem to top out. I think the lack of wings is significant with the Oclaro. Aside from the obvious improvement in beam quality and energy placement, it implies that there is indeed something different about the cavity in the Oclaro vs the two Mitsu diodes.

[CDBEAM]

CD,

I have to disagree with you as well, much as it pains me. If I remember correctly, the emitters of the P73 and G71 were directly measured by a member with an EM and the G71's emitter was only 70% as wide as the P73. Similar far field performance WITH IDENTICAL NEAR FIELD DIMENSIONS does not make a lot of sense.

Cylinders are not hard to dial in (the centration re the collimator is) and if the near field is measured as well as the far field then a pretty good estimate of divergence can be made. Using the 4mm lens from Optima makes the measurements and ratios easier, but they are not difficult.

At room temp, it looks to me as if Jordan's measurements show similar output for these two diodes up to about 1.4A where they both seem to top out. I think the lack of wings is significant with the Oclaro. Aside from the obvious improvement in beam quality and energy placement, it implies that there is indeed something different about the cavity in the Oclaro vs the two Mitsu diodes.

Mr.P,

It has been SOooo long ago....possibly the near field dimensions were not identical. Frankly....I tried so many different combinations....hard to keep it all straight....as I rethink my opinion !!!...and yes....if the emitter on the G71 is smaller....then divergence WILL be smaller with identical near field dimensions....the Laws of optics command this !!

As to the dial in process....well....with the style C-lens holder I have been using....it can be a bit more fidely....because the first lens/Plano concave sits in a channel....and is indexed back and forth...as one determines the optimal position. I suppose....with this lens epoxied to a movable base....things are more straight forward.

And....for the dial in for the Lens~LD....the centration is a pain.....BUT.....with the custom LD holder I have machined....there are three (3) 4-40 bolts that adjust the X-Y....Top, Left and Right....and the bottom location
is spring loaded. The entire back plate which applies spring tension to the diode is also spring loaded.....but....the springs are in pockets....which eventually give way to a hard clamp pressure....See Pic.

I designed this to make the centration easier...AND...with this unit the process is much easier....but....I must admit....I have gotten quite good at using the adjustable LD holder from LSP....and....while not as easy....it is ALOT smaller and surly less expensive !!...BUT...maybe not as precise ????

I also see less wing prominence on the Oclaro...and THAT is a good thing !!!....less garbage in...less garbage out !!!

CDBEAM=======>

[LaNeK779]

this is my contraption for centering the diode to the collimator

First, i focus the diode as best as i can to as far away as possible

then, knowing that dave's mount has the beam exit at 19mm height, i have marked a cross at 19mm height on a beam stop and i try to bring the spot to the "crosshair", which is dead center to opposite to where the diode emmits. I used a black metal to avoid much reflection. So the markings where i scrapped the paint are silver. This helps as the beams approaches center, because it hits the exposed metal and "lights up"

after centering, i re-check the focus far field. Sometimes i have to re-focus and re-center the diode a bit (which can be a pain). the diode centering definatly shifts a bit with focusing as can be seen here http://www.photonlexicon.com/forums/...1&d=1335137648

I am thinking of making a 1 -1,5 meter long such rig, just to get the centering even better (thanks to p1t8ull for the tip)



sometimes, if i want to check that the diode is dead parallel to the base plate, i expand the beam using a cyl lens and check against my markings

[planters]

I too have gotten better at using Dave's adjustable mounts. Leave the pins on the diode long and place longer than needed wires on them. With the added heat shrink tubing on each lead this set up produces a little "handle" that is easier to adjust. I later trim these wires to attach them to the Lasorb mounted on the top. I find rotating multiple diodes to the same exact angle to within 3 degrees more difficult, but amenable to the same free hand adjustment. This common rotation is critical to a small spot when using a common cylinder pair for multiple diodes.

I also find that the best alignment of the diode does not necessarily occur when the beam is gun-sighted to the diode mount as described by LaNeK. This is because these lenses, which are usually better than 1/100 lambda, are not necessarily mounted PERFECTLY in the center of the barrel. This is usually close,but sometimes the minor wings that show up above and below the main stripe will not be symmetrical unless the diode is shifted slightly up or down from this nominal starting position. I find the very smallest spot can be produced when the wings, all of them, are symmetrical.