Design and construction of a tunable 1014 nm ECDL to create rubidium-87 Rydberg states

We have designed and built a tunable ECDL to excite rubidium-87 atoms into high-lying Rydberg states as part of a three-photon transition. Our laser, based on a commercially available laser diode (LD), has a nominal linewidth of 1 MHz at 1014 nm with an available output power of 200 mW at a current of 400 mA. The beam is collimated using a NA = 0.55 aspheric lens to create a nearly circular Gaussian beam with a nominal 4 mm waist. The laser is tuned using a grating in the Littrow configuration with a subsequent tilt-cancelling mirror. We control the LD temperature using a closed-loop thermo-electric cooler. Our scheme uses 780 nm and 776 nm lasers to first drive the 5S-->5P-->5D atomic transitions. From here, the atoms will fluoresce to the 6P state. Following this, the nS and nD Rydberg states would be directly accessible with our laser.