A frequency reference based in VCSEL-driven dark line resonances in Cs vapor
John E. Kitching, N. Vukičević, Alexander S. Zibrov +4 more
Summary form only given. We report on recent experiments to use dark line coherent population trapping (CPT) resonances in cesium vapor as the basis for a compact frequency reference. The resonance is excited by directly modulating the injection current of a VCSEL at one-half the ground state hyperfine transition of Cs (4.6 GHz) to produce RF sidebands on the optical carrier. The laser output is then passed through a room-temperature cell containing Cs at its vapor pressure together with 8.7 kPa of Neon buffer gas and the transmitted optical power is detected in a photodiode. When the laser carrier is tuned half way between the two hyperfine components of the D/sub 2/ line at 852 nm, and the RF modulation frequency is adjusted to be equal to one-half the hyperfine splitting, the absorption of the sidebands through the cell is slightly reduced due to the CPT effect. As the RF frequency is scanned over the resonance, lock-in detection is used to produce a /spl sim/1 kHz wide dispersive error signal which is in turn used to stabilize the modulation frequency. The narrow signal is the result of the buffer gas, which reduces the time-of-flight broadening of the transition.
Quantum Electronics and Laser Science Conference•May 7, 2000•1 citation