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FrozenGate by Avery

405nm pointer meets Spectrometer

I

ix551

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Aug 27, 2010
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Hello there.

I recently got access to some of my campus' laser instruments for a second time.

The first time I could, I brought my 445 build to measure its power, but it LED'ed on me that same day, it was a little embarrassing :(

This time I went with my DX 405nm pointer link and a LOC diode.

NOTE: the batteries on the 405 were far from being full at the time of the experiments

I couldn't help but notice this little fellow:
358dh0x.jpg


After a lot of time setting the software and aligning the beam with my professor, we got these results:
166anbs.jpg


A stands for wavelength (nm)
I'm not really sure about B.

The Spectrometer's software also threw a huge and VERY detailed list of nm values with "B" values next to them, from 405.4 all the way to 534.4.
I'll post the relevant nm range:

406.35 - 20.027
406.39 - 30.63
406.43 - 35.027
406.47 - 50.63
406.51 - 78.027
406.55 - 152.63
406.59 - 269.027
406.63 - 415.63
406.67 - 636.027
406.71 - 904.63
406.75 - 1277.027
406.79 - 1727.63
406.83 - 2199.027
406.87 - 2836.63
406.91 - 3260.027
406.95 - 3509.63
406.99 - 4033.027
407.03 - 4285.63
407.07 - 4529.027
407.11 - 5350.63
407.15 - 6544.027
407.19 - 7923.63
407.22 - 9509.026
407.26 - 10037.631
407.30 - 9208.026
407.34 - 8220.631
407.38 - 7465.027
407.42 - 6420.63
407.46 - 4805.027
407.50 - 2994.63
407.54 - 1637.027
407.58 - 826.63
407.62 - 401.027
407.66 - 181.63
407.70 - 79.027
407.74 - 24.63
407.78 - 2.027

IMO it seems that the laser wavelength is really ~407.25 instead of the 405 DX advertises.

I also attempted to measure the output power with a nice little Spectra-Physics 407A. Youtube vid here.

After several measurements the pointer only gave ~24mw, I knew it was because of the AAA batteries, which weren't anywhere near full, so I tried to power the pointer with a lab PSU, trying very carefully to set the output voltage to 3v, but the PSU gave a ~11v spike and burned the laser.

I really need to learn how to use those PSU's this is the 3rd laser I've burned this way ...the cheapest one of them :(

I want to buy a new 445 diode and perform the same tests soon, I need some money first tho.
 





Die tolerance and wavelength shifting with heat accounts for your 407. If you get 4 more, you'd probably have 5 different wavelengths.

The 405 ebay pointer I have is 403nm.
The two PHRs I have are 407.5nm and 409.5nm
The 400mW O-like I have is 410nm.
 
Cyparagon said:
Die tolerance and wavelength shifting with heat accounts for your 407. If you get 4 more, you'd probably have 5 different wavelengths
Click to expand...

The temperature change does not shift a violet laser's wavelength much (compared to red lasers) One of my was operating at 414 nm :whistle:
 
But they still shift a bit ..... and also, the manufacturers themselves usually indicates the possible wavelenghts with a discrete shift (tolerance) possible ..... like the 445, that are indicated on the datasheets as 440/455nm tolerance range .....
 
My BDR-205 peaked at 408nm. Diode lasers are not known for their particularly narrow bandwidth.

If it were an HeNe, a "l" is all you should expect on that graph.
 
^Not unless the meter is worth 5-6 figures. It depends on how good the spectrometer is and how zoomed in the table is. All laser types show a similar distribution on mine.
 
Is the wavelength shifting also dependent on the current given to the diode? Assuming an almost perfect heatsinking system is being used so temperature remains the same
 
So you're saying if a diode was 405nm at 20mA and ambient, it would be 411nm at 0.5A while actively cooled? With all respect, that sounds like total BS.

I've got a PHR here that would be easy to test. Are these numbers of yours similar with a 100mW violet?
 
Cyparagon said:
So you're saying if a diode was 405nm at 20mA and ambient, it would be 411nm at 0.5A while actively cooled?
Click to expand...

During the measurement it was exactly like that: started with ~407@50mA and shifted to ~410@400mA. Other interesting result was the bandwidth increased from 0.4 nm to 1 nm. The temperature was held constant of the laser mount.

Cyparagon said:
Are these numbers of yours similar with a 100mW violet?
Click to expand...

Most likely.

My numbers are not out of the blues. Friend Google extracted 0.04 nm/K for violet lasers. A book cites 0.03 nm/mA for a F-P edge emitting lasers, and a figure is in google books Zappe Laser diode microsystems.
 
Alright, I just tested it. As I switch between 40mA and 120mA, the wavelength does change, but by less than 1nm. I'll assume it was not due to heat since I doubt the die can heat and cool within the half second it takes my spectrometer to respond to the change in current.

so (407.5nm-406.5nm)/(120mA-40mA) ≈ 0.01nm/mA, which is quite a ways from 0.04nm/mA.

lazeristasUVISIR said:
During the measurement it was exactly like that: started with ~407@50mA and shifted to ~410@400mA.
Click to expand...
Even your tests showed (410nm-407nm)/(400mA-50mA ) ≈ 0.01 nm/mA
 
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