Building an Interference Filter Laser for Laser Cooling

Producing a stable Bose–Einstein condensate requires cooling atoms to microkelvin temperatures using precisely tuned laser light. At the University of San Diego, we are building a rubidium-87 ultracold atom apparatus that requires lasers tuned near 780 nm. Commercial laser systems exist, but are often too expensive for undergraduate research and teaching labs. Instead, we have built our own cost-effective, reliable, and acoustically robust interference filter-stabilized external cavity diode lasers, along with the associated control electronics. These lasers incorporate a cat-eye lens arrangement for external cavity feedback, an interference filter for precise mode selection, a temperature-controlled aluminum cavity, and a protection circuit for diode longevity. We characterize our system through rubidium spectroscopy, demonstrating its suitability for Doppler cooling experiments. This work is supported by the NSF, Grant No. PHY-2427154.