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David Notebook: Difference between revisions
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==Daily Log==
'''8/25/14'''
I decided to go with the Moglabs wavemeter. We'll be modulating a signal from a pulsed laser sent through a crystal to further broaden the output. Zach had previously worked with this and had some spectrum data from it. I wrote a python program to calculate the broadened spectrum which took <math>10^{-6}</math> of each spectral component and shifted it up and down by 89.6 THz. The resulting spectrum should have a few tens of nWs total average power in the 640-840 nm range, which is where we'd first like to examine since we can use the same optics we already have. Moglabs says they can build us a custom wavemeter with enough sensitivity so that it should be able to measure this whole range at a resolution of ~1nm. It won't be ready until November, but there's a fair amount of setup to do in the meantime. '''Upload data tomorrow'''
We're wrapping up the experiment using 780 as the independent mixing beam. Now that we have it working pretty well, we want to plot pump power vs 633 power at the optimal pressure I found, and measure the transmitted pump and stokes beams at each pump power. Josh and I have been trying to do this on 8/22 and today, but have been having some locking/alignment issues. Today the 1064 current driver was fluctuating more than usual and even the setpoint values for temperature and current limit were fluctuating. Something seems to be wrong and we need to contact Vescent. We switched to the 1555 driver, which fixed the fluctuations, although it did not seem to improve performance. We tried switching the slow locking circuit to control the cavity piezo rather than the laser piezo. Josh said they had previously had a better lock doing this, but we did found it to be worse and ultimately switched back. We eventually got the pump locking again, although poorly, and got some 633 generation, although low power. It's hard to say what's wrong. Some days it just doesn't work very well, so hopefully it will be better tomorrow. Ideally we'd want to take all the data in the same morning or afternoon to reduce random fluctuations.
We want to make sure we're measuring 633 power and transmitted pump and stokes all at the same locking mode. It's hard to guarantee this unless we can measure them at the same time. We put in a flip mirror on the 780 side where the 1064 and 1555 reflect off the dichroic mirror. The beams then go to a prism and we will set up two power meters. So the plan is to get a good lock and measure 633, then quickly flip the mirror and record the 1064 and 1555 power values simultaneously.
'''8/13/14'''
The next step for the experiment will be to try to modulate a broadband signal. I'm looking if there's a cheapish wavemeter or spectrum analyzer option with high sensitivity, since we'd need to be able to look at a broad output rather than a narrow beam.
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