Glossary of Terms

\(\delta\): Induced retardation by the PEM
\(\omega\): Principal resonant frequency of the photoelastic crystal, for SolPol at 47 kHz
A: Peak modulation amplitude, for SolPol equals to 2.4048
ADC: Analog-to-Digital converter
CP: Circular Polarization
EQ3 SynScan: The current astronomical mount of SolPol
FOV: field-of-view
I_dark: The voltage measured by the instrument during dark measurement sequences
Lock-in: The SR830 DSP Lock-in Amplifier
LP: Linear Polarization
ND filter: Neutral Density filter
NOA: National Observatory of Athens
PANGEA: PANhellenic GEophysical observatory of Antikythera
PEM: Photoelastic Modulator
rms: root mean square
SolPol: Solar Polarimeter
SZA: Solar Zenith angle
TI: Total Intensity
UH: University of Hertfordshire

Definitions of Key Polarimetry Concepts

Birefringence: The optical property of a material having a refractive index that depends on the polarization and propagation direction of light. Light rays with perpendicular polarizations propagate one in the direction of the optical axis (ordinary beam) and the other on the direction imposed by the material (extraordinary beam).
Dichroic extinction: Extinction by aligned grains of dust, which causes starlight polarization. Light with its polarization vector lying along the projected long axis of the grain is absorbed more than light of the orthogonal polarization.
Dichroism: See Dichroic Extinction
DOCP: Degree of Circular Polarization, defined as the square root of the normalized V Stokes parameter
DOLP: Degree of Linear Polarization, defined as the square root of the normalized Q plus the normalized U Stokes parameters
Forward scattering: Light scattering towards the direct direction, aka at zero degrees
I: The first Stokes parameter (I), denotes the total light intensity
Mueller matrix: A 4x4 scattering matrix containing the linear relationship between polarization states of the incident light beam and the emerging light beam after passing through polarizing elements. Technique employed in Mueller polarimeters. when they obtain all the matrix elements.
Q: The second Stokes parameter (Q), denotes linearly polarized light state at 0 and 90 degrees
Stokes vector: Vector describing the complete light polarization state as [I,Q,U,V], at either point of the optical path.
U: The third Stokes parameter (U), denotes linearly polarized light at 45 and -45 degrees
V: The fourth Stokes parameter (V), denotes circularly polarized light