Figure 5.

Measurement setup. Two integrated cesium cells C1 and C2 (in the center of the magnetic shielding), the optical elements (lenses (L) for beam collimating, linear polarizers (P) and quarter-wave plates (λ/4) for the creation of circularly polarized light), and photodiodes (PD) for signal detection are located inside a shielding barrel with Helmholtz coils (not shown) for B₀ and B₁ field generation. The pump laser beam (amplified by a tapered amplifier (TA) and tuned by an intensity modulator (IM)) as well as the heating laser beam (not shown) are both fed into the shielding barrel via optical fibers. The pump power reference value (calibrated to those at the cells) is split off by a glass plate (G) and measured with a power meter (PM). The two PD currents (amplified by trans-impedance amplifiers (I/U)) and their difference deliver the actual measurement signals. The B₁ field is provided by a voltage-controlled oscillator (VCO). The different directions of B₀ and B₁ field in the M_x, Light-Narrowing (LN), and LSD-Mz mode are sketched separately. For M_x and LN only channel 1 is used with lock-in amplifier (LIA) signal processing, for LSD-Mz the difference of the signals from channel 1 and 2 is used.