UBC Undergraduate Research

Stabilized Reference Cavity and Laser Lock Cavers, Andrew; Gao, Tenny; Lam, Rudy


The “Stabilized Reference Cavity and Laser Lock” project is intended to produce a laser which is locked to a cavity in order to produce a significantly smaller bandwidth (or, in optical terms, “linewidth”) than the laser could normally achieve. The project was undertaken by Tenny Gao, Rudy Lam, and Andrew Cavers between September 26 2011 and January 10 2012. The overall goal of the project was to couple light from an 899-21 titanium sapphire ring laser (Ti:Sapph) into a cavity and use the transmission intensity through the cavity as error feedback to lock the laser to a specific frequency. The overarching tasks required to reach this goal were to assemble the Ti:Sapph laser, characterize the cavity, and test the quality of the laser lock. The deliverables of the project were: 1. Buying or building control electronics which allow the Ti:Sapph to be controlled by a user and by a feedback signal from a cavity. Deliverable A was found to be unnecessary, as a control electronics box (or "lockbox") was provided by the sponsor to control the laser. It was later found that this lockbox was broken in some way and required repair. 2. Assembling and bringing the disassembled 899-21 laser in the sponsor's lab into narrowband lasing. This deliverable was unattainable because although the 479 group brought the 899-21 laser into broadband lasing, the component required for narrowband lasing (the inter-cavity assembly, or ICA) could not be mounted into the laser and allowed to lase at the same time. The team ultimately resorted to locking another, identical Ti:Sapph laser in the sponsor's lab. 3. Locking the titanium sapphire ring laser onto a cavity, which in turn must be locked onto a frequency comb laser. Deliverable C was found to be impossible without replacing the initial cavity selection with a more stable cavity. The cavity the 479 group attempted to lock to was found to drift as quickly as 100 MHz a minute, endlessly. 4. Using an acousto-optic modulator to further correct the signal of the cavity-locked laser, using feedback from the cavity. Deliverable C was impossible to even initiate without Deliverable B complete. 5. Optionally, decreasing the line width of the laser further. This could be done by designing a new cavity to produce a more sensitive error signal and then adjusting the elements which rely on the cavity to control the laser‟s line width so that they can accept the new signal. Obviously, this deliverable was not reached by the 479 team. All of the components for the project, other than the titanium-sapphire ring laser, will need to be purchased by the ENPH 479 group from outside vendors. The group will rely on the budget of the sponsor‟s (Dr Kirk Madison) lab.

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