| 시설장비 설명 |
Mueller matrix ellipsometers (MMEs) are known to be less affected by noise if the compensators have a 132° phase shift between the slow and fast axis. This paper reports on the design and characterization of two custom-made achromatic compensators with minimal deviation from 132° retardation as a function of wavelength. The compensators are based on the dual Fresnel rhomb geometry. One pair was made of CaF2 and the other of fused silica. These materials were selected due to their extended transparency range and optical quality. The CaF2 compensators were experimentally characterized in the 450-8000 nm range, whereas the less IR-transparent fused silica prisms were characterized between 450 and 1900 nm. Both kinds of retarders possessed the necessary properties needed for a broad-band achromatic Mueller matrix ellipsometer, since they were both shown to give well-conditioned system matrices within the measured wavelength regions. Specifically, the condition number for the dual prisms used as a Polarization State Generator (PSG) or Analyzer (PSA) was determined to be in the range 1.73-1.96, close to the optimal 31/2 value. Simulations of the optimal retarder configuration in terms of incidence angles and rotation angles are presented and discussed. From literature values of the optical constants it is shown that the compensators perform well at ultraviolet wavelengths down to approximately 150 nm. |
