VCSEL Laser Source for CPT Atomic Clock Program

Vertical-Cavity-Surface-Emitting Lasers (VCSELs) are a key component in the development and ultimate commercialization of a new class of atomic clocks, the coherent-population-trapping (CPT)passive rubidium standard. Each of the available classes of VCSEL devices offer certain advantages and disadvantages for the CPT clock application. The proposed investigation will determine the optimum configuration(s) and attempt to develop reliable sources of supply. The laser characteristics of particular interest are optical power, threshold current, modulation bandwidth, relative-intensity noise (RIN) and optical linewidth. Optical power is of major interest as CPT performance is a function of the applied optical intensity. Threshold current levels affect the efficiency of the laser and, in turn the overall power consumption of the clock. RIN and optical linewidth contribute to the CPT signal-to-noise and the short-term stability, Allan Variance. Modulation bandwidth determines the efficiency with which the required optical sidebands can be generated. These interrelated characteristics will be measured and compared for each of the available VCSEL fabrication technologies in order to select an optimum approach for CPT clock applications.