This research covers the development and application of multiple low- noise high-bandwidth lockboxes to position the mirrors of four cascaded optical cavities using piezo actuators for frequency...Show moreThis research covers the development and application of multiple low- noise high-bandwidth lockboxes to position the mirrors of four cascaded optical cavities using piezo actuators for frequency locking with a preci- sion of 40 Hz. The design and fabrication of a custom printed circuit board that hosts two ARM-based microcontrollers for signal processing are elucidated. By measuring the impedance of the piezo actuators over a large range of frequencies, we found several electromechanical resonances ranging from a few kHz to a main resonance at 80 − 100 kHz. It was found that these resonances greatly impact the ability to lock the cavity to the laser source and thereby impose bandwidth limitation on the feedback. By avoiding excitation of such resonances by reducing the feedback bandwidth to below the first prominent resonance at 2.5 kHz, we were able to achieve a high quality lock of a single optical cavity. Using a reduced bandwidth of 250 Hz and a reduced modulation frequency of 1.9 kHz, we demonstrated the locking of four cascaded cavities and achieved an optical transmission of T ≈ 40%, limited mostly by optical alignment. Finally, we show an initial lock freeze procedure for three cascaded cavities in which 90% of the transmission during the locked state is retained for a period of 4.9 seconds, while providing no feedback on the piezos.Show less
In this thesis, we characterize and test a new MiM cavity for use in the Bouwmeester Optomechanics group. The cavity seems stable over time, though alignment offers some issues. The tip/tilt...Show moreIn this thesis, we characterize and test a new MiM cavity for use in the Bouwmeester Optomechanics group. The cavity seems stable over time, though alignment offers some issues. The tip/tilt alignment of the membrane was achieved to within 700 arcs eventually however. We also explore the use of finesse measurements to determine the absorbance of our membranes. We conclude that optical ring down measurements are preferable in our system and suspect that the PSG4 membranes have higher absorbance as compared to later generations. We present a scheme to determine the thermal gradient of our membrane in-situ, without any modifications required to the principle of the system. We do find, however, that the measurement is very sensitive to drift of the laser detuning. Finally, we explore the observed short term drift in our mechanical mode frequencies. We suspect the thermal expansion of some part of the system of adding additional strain to the membranes, and in doing so raising their mode frequencies, though the exact pathway remains unclear.Show less