[Daniel, Sander, Torrey]

We wanted to see if we could lock our michaelson in the lab using the frequency of the laser. However, the external modulation ports on the turnkey laser we have has an input voltage requirement of +/- 5V. The manual says this modulates the current at 2 mA/V. The graphs on thorlabs say changing the current by ~20mA should correspond to changing the wavelength of the laser light by order 10 pm. If our interferometer has interference fringes lambda/2 = 775 nm apart and we can only modulate by about 10 pm maximum, we will never be able to lock a michaelson using the laser frequency alone.

We were able to inject a 150 kHz signal into the AC modulation port of the laser and can directly read that out on a PD, but only by blocking one of the arms of the michaelson, suggesting this is purely modulating the amplitude and not frequency. We also tried using the temperature unsuccessfully, which does not have specs online of its mA/V response.