  In this work, we present a comprehensive and comparative analysis of two
detection modalities, i.e., polarization rotation and absorption measurement of
light, for a double resonance alignment based optical magnetometer (DRAM). We
derive algebraic expressions for magnetometry signals based on multipole
moments description. Experiments are carried out using a room-temperature
paraffin-coated Caesium vapour cell and measuring either the polarization
rotation or absorption of the transmitted laser light. A detailed experimental
analysis of the resonance spectra is performed to validate the theoretical
findings for various input parameters. The results signify the use of a single
isotropic relaxation rate thus simplifying the data analysis for optimization
of the DRAM. The sensitivity measurements are performed and reveal that the
polarization rotation detection mode yields larger signals and better
sensitivity than absorption measurement of light.
