Optimizing a Highly Stable Diode Laser for Spectroscopy and Atom Trapping John E. Sohl Caleb Z. Trammell Weber State University Ogden, UT

Overview Brief History What is an ECDL? Carl Wieman’s ECDL design Other ECDL designs Our ECDL design Results and current status

History Carl Wieman’s group, AJP papers: 1992: A narrow-band tunable diode laser system with grating feedback, and a saturated absorption spectrometer for Cs and Rb. 1992: A narrow-band tunable diode laser system with grating feedback, and a saturated absorption spectrometer for Cs and Rb. 1995: Inexpensive laser cooling and trapping experiment for undergraduate laboratories. 1995: Inexpensive laser cooling and trapping experiment for undergraduate laboratories. Nobel Prizes: 1997: Laser trapping 1997: Laser trapping 2001: BEC 2001: BEC 1999: NSF workshops

Current Status Numerous papers on improved laser design since ~1999. Moderate number of undergraduate laboratories doing saturated absorption. A few doing atomic trapping. Why? Not Easy and Laser Stability

Goal: Wavelength Stability These issues have been covered in our other paper today. Cavity size (mode spacing and  or  ) Thermal mass and stability Ease of construction and operation

Laser Gain Profiles From: S.J.H. Petra, 1998

Laser Design Extended Cavity Diode Laser – ECDL Feedback from the diffraction grating (G) forces the wavelength to a specific value.

Other Designs

Our Design Simple Easy to align and assemble Easy to build Inexpensive Low thermal mass Short cavity

Results and Current Status Laser has been built and is being tested. Earlier modifications have resulted in frequency stability of ~300 kHz (<1 part in ~10 8 ) for several hours at a time. (Wieman got 3.5 seconds.) Expecting factor of 3 improvement with new design. Should be operational in 2-3 days.