Event Title

Advanced Cold Molecule Electric Dipole Moment Experiment Automatic Laser Locking System

Session Number

Project ID: PHYS 23

Advisor(s)

Collin Diver; Northwestern University

Discipline

Physical Science

Start Date

19-4-2023 9:35 AM

End Date

9-4-2023 9:50 AM

Abstract

The Advanced Cold Molecule Electron (ACME) Electric Dipole Moment (EDM) experiment seeks to place a more precise upper limit on the electron EDM than its predecessors. Part of this increased precision will result from using an External Cavity Diode Laser (ECDL). The Standard Model predicts an electron EDM that is too small to measure with current precision. The experiment will search for energy shifts in certain molecular states of a cryogenically cooled, laser-ablated beam of thorium monoxide in an electric field. These energy shifts would indicate the presence of a large electron EDM.

The experiment relies on optical mechanisms that transform lasers into stable, useful forms. Our investigation focuses on creating a system to automatically lock the frequencies of the experiment’s lasers to a stable cavity, so they will interact correctly with the molecular beam. To do this, we implement the Pound-Drever-Hall (PDH) technique to generate an error signal from laser frequencies near the cavity resonances. The LabView program serves as a feedback loop that periodically analyzes the current PDH error signal, determines the new correct frequency offset, and re-locks the laser with that new offset. This way, we minimize the frequency drift of the lasers over time.

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Apr 19th, 9:35 AM Apr 9th, 9:50 AM

Advanced Cold Molecule Electric Dipole Moment Experiment Automatic Laser Locking System

The Advanced Cold Molecule Electron (ACME) Electric Dipole Moment (EDM) experiment seeks to place a more precise upper limit on the electron EDM than its predecessors. Part of this increased precision will result from using an External Cavity Diode Laser (ECDL). The Standard Model predicts an electron EDM that is too small to measure with current precision. The experiment will search for energy shifts in certain molecular states of a cryogenically cooled, laser-ablated beam of thorium monoxide in an electric field. These energy shifts would indicate the presence of a large electron EDM.

The experiment relies on optical mechanisms that transform lasers into stable, useful forms. Our investigation focuses on creating a system to automatically lock the frequencies of the experiment’s lasers to a stable cavity, so they will interact correctly with the molecular beam. To do this, we implement the Pound-Drever-Hall (PDH) technique to generate an error signal from laser frequencies near the cavity resonances. The LabView program serves as a feedback loop that periodically analyzes the current PDH error signal, determines the new correct frequency offset, and re-locks the laser with that new offset. This way, we minimize the frequency drift of the lasers over time.