We present a method for calibrating polarimeters that uses a set of well-characterized reference polarizations
and makes no assumptions about the optics contained in the polarimeter other than their linearity. The
method requires that a matrix be constructed that contains the data acquired for each of the reference polarization
states and that this matrix be pseudo-inverted. Since this matrix is usually singular, we improve the
method by performing the pseudo-inversion by singular value decomposition, keeping only the four largest
singular values. We demonstrate the calibration technique using an imaging polarimeter based upon liquid
crystal variable retarders and with light emitting diode (LED) illumination centered at 472 nm, 525 nm, and
630 nm. We generate the reference polarizations by an unpolarized source, a single polarizer, and a Fresnel
rhomb. This method is particularly useful when calibrations are performed on field-grade instruments at a
centrally maintained facility and when a traceability chain needs to be maintained.
Polarized light imaging has been used in the past for skin-cancer edge detection from skin lesions. In the standard
imaging modality, the source, detector, and sample are usually aligned in the same plane, and the effect of the air-skin
boundary is minimized using a glass slide with an index matching fluid. In this study, we investigate polarized light
imaging of skin surfaces using a novel instrument that enables out-of-plane illumination. Stokes vector images are
acquired for any one of sixteen different illumination directions and used to study the effect of skin roughness as well as
surface and subsurface scattering. We show that the effect of skin roughness can be minimized or enhanced, depending
upon the incident direction and polarization. In the former case, the need for a glass slide with an index matching fluid
can be reduced. In the latter, surface topography can be more clearly discerned.
We present a novel spectro-polarimetric instrument based on hemispherical backscattering for the assessment
of superficial skin lesions. The system is capable of capturing polarized light images non-invasively.
The effect of the rough skin backscattering is eliminated with the use of out-of-plane illumination. A glass
slide with an index matching fluid, commonly used in polarized light imaging, is no longer necessary. The
system is composed of sixteen polarized light sources that provide red, green, or blue illumination. The light
sources are distributed on a hemispherical shell, and each source produces a collimated beam incident on the
center of the hemisphere. A Stokes vector imaging system is mounted on the shell at an oblique angle to the
sample normal and consists of a 12-bit scientific camera, two liquid crystal variable retarders, and a fixed polarizer.
Stokes vector images of light scattered towards the camera direction are generated for each source. A
useful decomposition of the Stokes vector is presented. Examples of images generated by the system are presented.
Semiconductor Optical Amplifiers (SOAs) are of central interest as multifunctional, easy-to-integrate components for the development of future optoelectronic systems. Their dependence upon the incoming light polarization is a well-known, but still debated, issue in the context of emerging optical telecommunication networks, fueling the need for a detailed polarimetric characterization of such structures.
In this paper, we present what we believe to be the first systematic polarimetric analysis within the frame of the Mueller-Stokes formalism of an integrated InP/InGaAsP SOA around 1550 nm. The challenge stems from the amplifying, active, spectrally broadband and nonlinear nature of the component. For the sake of our study, we have developed a highly sensitive, free-space, polarimetric set-up, with the additional experimental challenge induced by the spatial constraints of a guided-wave device, most notably in terms of light injection. Physical phenomena (intrinsic noise contribution of internal sources, carrier saturation due in particular to Amplified Spontaneous Emission, modal birefringence for index and gain...) responsible for the polarization dependence of the amplification process are identified, and discussion of the data highlights the need for an extended matrix formalism taking explicitly internal sources into account.
Polarimetry technique allows one to study the changes induced by a physical system in the polarisation of electromagnetic waves. As its optical response is greatly affected by the polarisation state and wavelength of the incident light, a class of powerful polarimeters has been developed to measure the polarimetric response of a sample over a wide spectral band. Such a device, therefore, allows one to greatly increase the number of data about the sample of concern. The polarimeter of that sort we developed and implemented is operating with a pulse source. Moreover, by running a novel and theoretical model to describe the compensated waveplates used we focused on the reduction of systematic errors. This model takes into consideration the elliptical birefringence of each rotating device. In doing so, the precision currently given for the Mueller matrix elements is drastically improved. Simulations enabled us, first, to determine the measurement error on each element of the Mueller matrix without a sample and, second, to adopt a method of calibration. Experimental results and corrections highlight the interest of taking elliptical birefringence and dichroism into account. This calibration procedure led us to develop a compensated-waveplate characterisation bench. Then, a statistical study allowed us to greatly reduce and quantify the residual errors inherent in a measurement.