Blog 8: Laser power dependence

Welcome back! I started thinking about how I would complete my project goal of calibrating the cryostat. After talking to Dr. Smallwood again, I unfortunately came to the conclusion that I could not do this very well. However, he suggested that one possible source for the temperature displayed being inaccurate would be if the laser is heating up the sample and the thermometer not registering it, so to test this, we could collect a set of data with the laser hitting the sample at different brightness or power. So, we inserted a laser power meter and using a tunable neutral density filter in front of the laser, we can adjust how much of the laser we let through. After we adjust we take out the meter to collect photoluminescence and we repeat to collect a range of data for different laser powers. I extracted all the fits again (see blog 3 if you want to see more of this process, though it was more successful this time), and I saw that the peak positions did not change at all.

My other parameters changed which makes sense since greater laser power excites more electrons and we get more photoluminescence, and I kind of observed the decrease in intensity as I was taking the data. Ultimately, I think we can conclude that the laser does not contribute to any significant temperature increase unaccounted for. This experiment was done with the HeNe laser I talked about last blog, so we will do temperature-dependence with this one next to compare with our HeCd data. Stay tuned!