505nm and 480nm diode RESULTS

[Singlemode Laser]

Also, I've measure diodes for Singlemode Laser who works at the University of Berlin and the diodes I measured for him are very close to his spectroed measurements.

I can confirm this. I always calibrate my spectrometer with a measurement using a wavemeter with sub pm or 0.001nm accuracy. (I use the same diode I plan to measure and grating feedback to achieve sm operation that is needed for proper wavemeter operation.)

Without calibration the spectro can drift significantly over the timeframe of months. Moving and temperature cycles isually increase the drift or induce a "jump" in the measured wl.

Singlemode

 

[ultimatekaiser]

I wasn't aware these diodes started to come with internal protection. I have an older SB147EC91 and it runs at 300mA just fine (I know I'm pushing).

The diode doesn’t, the power supply I’m using does. If it detects a current surge that takes it higher than I allow, it shuts down the diode current source to keep it from popping. I had a hard limit of 200mA set.

I can confirm this. I always calibrate my spectrometer with a measurement using a wavemeter with sub pm or 0.001nm accuracy. (I use the same diode I plan to measure and grating feedback to achieve sm operation that is needed for proper wavemeter operation.)

Without calibration the spectro can drift significantly over the timeframe of months. Moving and temperature cycles isually increase the drift or induce a "jump" in the measured wl.

Singlemode

Yes. I mentioned this earlier.

 

[Zom-B]

When you do, ask for Norm Hoffer. He's a hell of a nice guy and was great to work with. I'll never forget him.

Every country has it's own Ocean Optics office, so it's hard to get Norm Hoffer at the dutch office. Our spectrometer (which was last calibrated 3 years ago!) had to be sent to Germany incidentally but the one organizing everything is still someone from the Dutch office. Our spectrometer (JAZ) will be reconfigured for ~390-1050nm instead of 190-1050. Those frigging things even need a new CCD sensor of the same type just because the anti-harmonics filter is built in to it or something. $$$

 

[paul1598419]

I'm certain you are right, but I meant for UK who is in the states as am I.

 

[ZRaffleticket]

Question for either Paul or Singlemode (or anyone with a really good spectro and these diodes)

Is the linewidth on these diodes really high? I just put the 480nm diode I have through a diffraction grating and I can make out (albeit barely) a gradient in color in the spots it produces far from the center. It's much more so a line than a spot when you get to the far edges... and there's a visible gradient in color, deeper blue toward the origin of the diffraction grating and lighter farther away from it:


No other lasers but these sharp diodes, at least that I have, do this.

 

[paul1598419]

Not nearly as wide as you are trying to say here. Really just a nm or two at the very most. If you are seeing a deeper blue color, it tends to indicate a shorter wavelength. Though I can't say what you are seeing. Direct diodes don't have extra lines like an argon or other ion lasers. I would have to see it myself to try to figure out what you are seeing. Maybe Singlemode might know off hand. The multi-line 532nm DPSS lasers I have are very close to the major line of 532nm. Not enough to see a difference in color.

 

[ZRaffleticket]

Some diodes do have multiple lines, the 485 also has a second strong line a bit above 480nm. I also had an old nich1a 473nm diode that was multiline 476/480. Hopefully singlemode can chime in then. Here's a better shot:



In person, it's roughly the same brightness across

 

[paul1598419]

Were these multimode diodes? It would be news to me that a single mode direct laser diode was capable of multi lines without some grating tuning or another way to shift its center wavelength. I have looked at the spectrum of many of these diodes and have yet to see an additional line.

 

[ZRaffleticket]

As far as I can tell they were all single mode

 

[Atomicrox]

Paul, there are single mode diodes with multiple lines. Many 980nm lasers do, and they have been verified by multiple people with spectrometers.

ZRaffleticket, what kind of grating are you using? Are you sure this isn't just a defect on it?

 

[ZRaffleticket]

I'm not sure actually. It's not areally good one I don't think, I've had it for a few years so I don't remember where I bought it...

It only does this on the new sharp diodes though. Doesn't do this on any of my other lasers (save the 485nm which has two distinct lines)

 

[Atomicrox]

I tried this with a crappy flexible plastic grating and a pocket spectroscope on 505nm and 532nm. With the plastic grating the 505nm spreads quite a bit while the 532nm maintains a small dot, but it seems like the distortion is due to the thick beam. With the spectroscope both show a single line.

 

[Zom-B]

ZRaffleticket, are you at just lasing threshold? Those lines look like what I see through my spectroscope with a 505nm diode. Your images are also quite noisy. With increasing current it starts like a smear (LED mode or what you'd see with COD). When threshold it hit, it starts lasing at the lowest (bluest) end of the line. As you pass threshold current, the wavelength swiftly increases to the nominal value.

 

[paul1598419]

Paul, there are single mode diodes with multiple lines. Many 980nm lasers do, and they have been verified by multiple people with spectrometers.

I guess I should have been more specific, but we were talking about VIS diodes. Multimode IR diodes do have many lines and especially large IR diodes used to pump SHG. That is a totally different example than this, however. It is not unusual to see it in single mode IR diodes, I would suspect.

 

[ZRaffleticket]

I'm far from threshold - I'm running at over double the recommended current. 275mA

ZRaffleticket, are you at just lasing threshold? Those lines look like what I see through my spectroscope with a 505nm diode. Your images are also quite noisy. With increasing current it starts like a smear (LED mode or what you'd see with COD). When threshold it hit, it starts lasing at the lowest (bluest) end of the line. As you pass threshold current, the wavelength swiftly increases to the nominal value.

 

[Zom-B]

I've been a fool. I have a hypothesis. I might be totally off though. But I want to see how this story unfolds before revealing it. To proof that my hypothesis won't be affected by future posts, I've encrypted it and will reveal the key later.

EnCt2a3b624bb5d719db809bb4518764cf7afab0e3fd4a3b624bb5d719db809bb4518L==Z=Tj=cQM
J+jr3JFqOsfYr8DYtzTAmi+MwfA92vHbOzgxFxaXkxooA94IjzKBKdGG5B5gK9LCdx99JHVgJ5WzGN7m
RklM/bJhvresZbfQKu246PS82iCBWn37T/iyZSW91X4yQry6S7kyxeFual/OT6sW30Ji/3p4fjj7Rh1T
l007L1RMX5hQuxsXe+1YTE8iFGNLW2opJO0Aj6RbvQsPPMhAotHDkSkYQCetnTKMXHgy8cZkMgc58HjS
4SJH4iqrJFFgvQDJKkHbdCWaXxWRRRShm4Ra4m8hRt5TbpF4XzOdpOs3JuvVpmo4/0nE3h0k0LxnKboP
2l5hq9n+qd8xuH4Nb2gasXIqxflkJ0BVQieRlSfkWuz80TdELS4CYoA==IwEmS

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