Schematic of laser system. The system consists of three external-cavity diode lasers. The reference laser serves as an optical frequency reference used to stabilize two high-power lasers. The frequency of the master laser is stabilized with respect to the reference laser through the use of an optical phase-locked loop. The slave laser is phased locked to the master laser by using another optical phase-locked loop.
Schematic of an optical phase-locked loop. An optical phase-locked loop consists of a master laser, a slave laser, a phase detector, and a loop filter.
Schematic of feedback electronics designed for the OPLL used to stabilize the frequency and phase of the master and slave lasers.
Measured beat-note signal between master and slave lasers. (a) Curve (i) shows the beat-note signal when only the relative frequency between the master and slave lasers is stabilized while curve (ii) shows the beat-note signal when the lasers are phase locked (resolution/video bandwidth=10 kHz). The effect of the OPLL is to narrow down the beat-note signal. (b) Expanded view around the narrow beat-note signal that is obtained with the OPLL (resolution/video bandwith.
Atomic configuration used for EIT measurements in .
EIT signal in . (a) shows the measured, curve (i), and calculated, curve (ii), transmission spectrum for the probe beam. The use of phase-locked lasers made it possible to obtain a contrast of 70%. The periodic structure in the transmission spectrum is due to discrete signal used in OPLL to compensate for the frequency scanning ramp. (b) shows the calculated absorption spectrum corresponding to the measured transmission spectrum. A reduction in the absorption coefficient of 92% was obtained.
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