550
M. Saini et al.
2.1.4 Depolarizer
A depolarizer is a wedge-shaped birefringent crystal which is used to convert a
partially polarized light coming from a light source into truly unpolarized (i.e.
completely random) light [3, 15]. In fact, when partially polarized light is incident
at different places of a wedge-shaped birefringent crystal then due to progressive
variation in the thickness of the crystal, a progressive phase-difference is generated
which leads to unpolarized light.
2.2 Different Types of Ellipsometry Measuring Techniques
As it is explained earlier that the basic principle of ellipsometry is to detect the
change in the polarization state upon reflection or transmission from the specimen.
For instance, s- and p-polarized light are incident on a specimen at the Brewster angle
and by measuring the change in the polarization state of light, the optical constant and
film thickness of the specimen can be precisely obtained. Ellipsometry instruments
can be classified in various configurations on the basis of the orientations of optical
elements in ellipsometry [3] viz. rotating-compensator ellipsometry (RCE), rotatinganalyzer ellipsometry (RAE), phase-modulation ellipsometry, etc. Basically, Stokes
vectors are measured by ellipsometry, albeit, Stokes vectors measured with each
configuration of ellipsometry are different and it leads to a variation in the error
involved in a measurement. Some of the configurations of ellipsometry setup are
briefly described in the following sections.
2.2.1 Rotating-Analyzer Ellipsometry (RAE)
In this configuration of ellipsometry setup, there is a source of light followed by a
polarizer on the light incident side, however, a continuously rotating analyzer and
a light detector are situated on the reflection side [3]. When rotating analyzer gets
a desired rotation position, polarized light starts to scan the specimen. In addition,
RAE with compensator can measure all the Stokes vectors in two measurements
with different compensator settings. On the other hand, RAE does not show any
wavelength dependence (i.e. achromatic).
2.2.2 Rotating-Compensator Ellipsometry (RCE)
Rotating-compensator ellipsometry has a source of light followed by a polarizer
at incident side whereas a rotating compensator, non-rotating analyzer, and a light
detector are situated at the reflection side [3]. This configuration of ellipsometry
M. Saini et al.
2.1.4 Depolarizer
A depolarizer is a wedge-shaped birefringent crystal which is used to convert a
partially polarized light coming from a light source into truly unpolarized (i.e.
completely random) light [3, 15]. In fact, when partially polarized light is incident
at different places of a wedge-shaped birefringent crystal then due to progressive
variation in the thickness of the crystal, a progressive phase-difference is generated
which leads to unpolarized light.
2.2 Different Types of Ellipsometry Measuring Techniques
As it is explained earlier that the basic principle of ellipsometry is to detect the
change in the polarization state upon reflection or transmission from the specimen.
For instance, s- and p-polarized light are incident on a specimen at the Brewster angle
and by measuring the change in the polarization state of light, the optical constant and
film thickness of the specimen can be precisely obtained. Ellipsometry instruments
can be classified in various configurations on the basis of the orientations of optical
elements in ellipsometry [3] viz. rotating-compensator ellipsometry (RCE), rotatinganalyzer ellipsometry (RAE), phase-modulation ellipsometry, etc. Basically, Stokes
vectors are measured by ellipsometry, albeit, Stokes vectors measured with each
configuration of ellipsometry are different and it leads to a variation in the error
involved in a measurement. Some of the configurations of ellipsometry setup are
briefly described in the following sections.
2.2.1 Rotating-Analyzer Ellipsometry (RAE)
In this configuration of ellipsometry setup, there is a source of light followed by a
polarizer on the light incident side, however, a continuously rotating analyzer and
a light detector are situated on the reflection side [3]. When rotating analyzer gets
a desired rotation position, polarized light starts to scan the specimen. In addition,
RAE with compensator can measure all the Stokes vectors in two measurements
with different compensator settings. On the other hand, RAE does not show any
wavelength dependence (i.e. achromatic).
2.2.2 Rotating-Compensator Ellipsometry (RCE)
Rotating-compensator ellipsometry has a source of light followed by a polarizer
at incident side whereas a rotating compensator, non-rotating analyzer, and a light
detector are situated at the reflection side [3]. This configuration of ellipsometry