9mm 808nm + crystal and no green?

[Danjoo]

Hi Guys,

After spend some time with Flashlights iam back in Lasers.

For a friend i have bought this green laser.
Its a "200mw" china build.
After a few minutes runtime it dies, i dont want to send to china.

I want to repair it.

After disassembling this, i found a 9 mm diode.
I buy another diode and try to rebuild the laser.

The diode is connected to the driver and running at around 350mw, measured by my Laserbee powermeter.

I tought when i replace the diode and put the original crystal on it i will see a green shine.
But nothing not a single bit green light beam visible.

Is the difference the Problem?

I dont have Datasheets or numbers to google for this diodes, maybe a experienced guy can tell me if I buy crap? Is it maybe a multimode or totall different beam angel right from the emitter?

Need some help Please?

Thanx in Advance


Daniel


The replacment diode looks complete different to the Original one:
The caned one is the replacment!

Is the difference the Problem?
Is this fixable?

 

[Tech_Junkie]

I would say it an alignment issue, and its not user friendly to fix. The diode could be a different type, ect.. I would have sent it back.

 

[photonaholic]

Try turning (rotate) the diode a little at a time, hope it helps.

 

[Danjoo]

Right now the original carrier of the crystal is direkt on the canned diode surface.

Ok maybe its not good mounted in the carrier.


Can someone tell me more about "different type" what you said.

Its the different type of beam angel its better to collimate bevor crystal?

thanx

Daniel

 

[photonaholic]

I am sorry Daniel, I am having just a little difficulty with our language barrier.

 

[Asherz]

Right now the original carrier of the crystal is direkt on the canned diode surface.

Ok maybe its not good mounted in the carrier.


Can someone tell me more about "different type" what you said.

Its the different type of beam angel its better to collimate bevor crystal?

thanx

Daniel

If I remember correctly, the polarization of the light from the diode is important, so as mentioned above rotate the diode a little at a time and see if you get any green light. Different diode shouldn't make a difference as long as it's outputting the same power and wavelength as the original.

 

[Tech_Junkie]

Well you are replacing an open can with a closed can. It might not work.

 

[Hemlock_Mike]

Also, Some 808 nM diodes purchased from ebay or other source may not be 808 nM but +/- 5 nM. The input must be real close to 808. Rotating the pump diode might help -- That is how most of us do it.

HMike

 

[Danjoo]

The crystal on the diode, direkt on the diodes face.

 

[Danjoo]

Many thanks, rotating and testing alot.

Now its running, way to less power, only 22 mw measured.

Its eventually better to collimate the ir bevor pumping in the crystal?


Daniel

 

[Hemlock_Mike]

Daniel ---

How did you measure the 350 mW output from the 808 pump diode? That's not enough for 200 mW of green considering conversion efficiency.
You need to supply some more info. What is the current to the 808 pump diode?
How are you measuring power?
I'm glad the info we provided here helped but now the fine tuning begins.
What is the new pump diode rated at for output?
Columinating before the crystal is done with exterior lenses or an FAC coating on the diode normally.
HMike

 

[Danjoo]

Hi Mike,

The Diode is rated @ 500mw 808nm supplier said.

The 350mw is just to find the right place for the crystal, i can get up to 700mw for short times. Then the driver and the diode get very fast quit hot.

All the outputs are measured with my laserbee.


The 22mw green beam is generated from the 350mw 808 radiation.


- I put the crystal set direkt on the diodes face.
The diode is the canned one:
did i miss a fast axis collimation lens?
Or is it on the diodes window as a fresnel style? I cant see something like that.

Many thanx for taking time for me

Daniel

 

[photonaholic]

You can delete it yourself, follow these steps.

 

[HIMNL9]

@Danjoo:

Probably, one of the facts that give you less power, is that the replacement is canned, so is loncer than the original one.

From your pics, it looks as the crystal holder, originally, was more low posed on the external ring, not on the diode), and now is more far from the chip (cause the can keep it higher) ..... with small crystals, some manufacturers, uses open can diodes on purpose, so they can keep the crystal more close to the diode chip (usually half millimeter or less), increasing the quantity of IR that the diode pump in the crystal .....

You must try with an open can diode, or try to decan the one that you have (but if you are not used to work with laser diodes and precision tools, this may be a risky operation, you may ent breaking the spare one) ..... also, the crystal must be not only rotated for get the correct polarization angle, but also centered (aligned) with the chip, for minimize the loss of IR.

And, ofcourse, the crystal faces must be clean (hope you have not touched them with fingers )

 

[ElektroFreak]

Your best bet is to use a simple collimating lens to focus the 808 (assuming your diode is 808 with a low tolerance) to a point just past the input surface of your crystals. Direct-coupling (placing the diode right next to the crystals) does work, but it's easier and more efficient if the 808nm light is focused into the crystals.

 

[jaycey]

Out of curiosity, how do you work with ir when you cant see the beam?

Digi cams?