Birefringent phase demodulator: application to wave plate characterization

Abstract

The scope of this work is to present a phase demodulator that enables the recovery of temporal phase information contained in the phase difference between two signals with different polarizations. This demodulator is a polarization interferometer that may consist only of a uniaxial crystal slab and a polarizer sheet. The phase shift between two orthogonal components of the electric field is translated into space by means of birefringent crystals, which act as demodulators or phase analyzers with great robustness. The experimental scheme utilized is based on a simple conoscopic interference setup. Each portion of the space in which the interference pattern is projected contains not only the unknown temporal phase we want to recover, but also a phase shift due to the uniaxial crystal itself. The underlying idea is developing simultaneous phase shifting with uniaxial crystals. Thus, different phase recovery techniques can be applied in order to maximize their ability to track high-speed signals. Depending on the characteristics of the fringe pattern, it will permit phase recovery via different classical procedures. In order to prove the demodulator under different experimental and signal processing schemes, we employed it for wave plate characterization. The results obtained not only allow some wave plate features such as axes determination and retardance to be characterized, but also prove the working principle and capabilities of the demodulator.

A birefringent polarization modulator: Application to phase measurement in conoscopic interference patterns

“…Due to its simplicity and robustness, the preferable method to achieve this is grinding an interface before the crystal sample. [4][5][6]14,16 Some DUTs can have their first interface ground (at x = 0) but some samples can be severely damaged and a piece of ground glass must be interposed before the DUT. In order to simplify the analysis, we assume that the samples considered are uniform crystals.…”

“…(4)) and modifies the fringe pattern. 14,18 We follow the procedure indicated in Ref. 28 in order to recover the phase map of the DUT.…”

“…(2)). It should be noted that a calibration of the BPM 14 or a self-calibrating algorithm is needed. The interferograms of Figs.…”

“…[4][5][6][7][8][9] Furthermore, conoscopic techniques have several applications like multipurpose rangefinders, 10 surface inspection, 11 differential interference contrast microscopy, 12 visualization of polarization properties of optical vortex beams, 13 and waveplate characterization. 14 Accordingly, conoscopic fringe patterns are theoretically described with different levels of approximation by means of the phase shift introduced between the beams that propagate through a crystal sample. [15][16][17] However, the analysis techniques for conoscopic interference patterns described in the bibliography are generally based on very simple methods such as fringe counting or isochromates visualization.…”

Deformaciones de haces cilíndricos y cónicos al atravesar una placa plano-paralela de cristal uniaxial

“…En los últimos años hemos obtenido expresiones analíticas generales [12,13] que han permitido el desarrollo de polarímetros solares [14] e interferómetros para diagnóstico de plasma [15,16]. Asimismo, los estudios de patrones de interferencia conoscópicos [17] nos han permitido desarrollar moduladores y demoduladores de fase birrefringentes [18,19,20].…”