Variable Optical Attenuation Using Stretchable Polymers

In this study, optical attenuation capability of a polymeric slab is investigated. The structure is composed of a stretchable polymer slab (PMMA is chosen for that study); sliding blocks that are used for properly tilting the slab; idler pulleys (two pieces, placed diagonally); and adjustment sockets (two pieces, placed diagonally) for precise arrangement of the slab’s tilt angle. Optical response of the dielectric slab could be modified using strain/stress capability of PMMA layer and hence, the output intensity as well as intensity ratio of p-/s-polarizations is controlled via proposed attenuator system thanks to the tilting effect and the possible multilevel reflections/transmissions inside the polymeric slab. Especially reaching towards the polarizing (Brewster) angle, the difference in the calculated total transmittance between both polarizations becomes maximum. In the case of PMMA slab, the value of Brewster angle equals $\theta_{brew}\tan^{-1}\left(\frac{n_{t}}{n_{i}}\right)=56^{\circ}$. Corresponding intensity of the output beam for p- (s-)polarization increases (decreases) from $T_{tot}=0.93(0.93)$ to 1.0(0.76) within the interval $\theta_{i}=[0^{\circ}-\theta_{brew}]$. In the range of $\theta_{i}=[\theta_{brew}-90^{\circ}]$; however, total transmittance value decreases from $T_{tot}=1.0(0.76)$ to $T_{tot}=0(0)$ for p-(s-)polarization. The intensity ratio is another critical parameter defined as $\Gamma=T_{tot}^{(s-)}/T_{tot}^{(p-)}$, which shows a falling tendency to the increase of $\theta_{i}$. The intensity ratio equals $\Gamma=0.76$ in the case of Brewster angle and it is higher than $\Gamma \gt 0.5$ in the interval of $\theta_{i}=[0^{\circ}-79.4^{\circ}]$. It can be deduced from the theoretical calculations that the output power division could be controlled by adjusting the tilt angle of the PMMA slab and a variable power attenuation could be achieved via the proposed stretchable optical device.