Abstracts - Dipartimento di Elettronica Applicata
Abstracts - Dipartimento di Elettronica Applicata
Abstracts - Dipartimento di Elettronica Applicata
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Meta 2010 & FEM 2010 – Rome, 13-15 December 2010<br />
Optical performances of micron-sized CMOS<br />
image sensors using metallic planar lenses<br />
Rino Marinelli and Elia Palange<br />
Università degli Stu<strong>di</strong> dell’Aquila, <strong>Dipartimento</strong> <strong>di</strong> Ingegneria Elettrica e<br />
dell’Informazione<br />
L’Aquila, Italy – E-mail: rino.marinelli@univaq.it<br />
CMOS image sensors equipped with metallic planar lenses have been<br />
designed and simulated by CST Microwave Stu<strong>di</strong>o. The increase of the spatial<br />
resolution of CMOS image sensors implies the reduction of their pixel<br />
<strong>di</strong>mensions. It has been demonstrated that for pixel size smaller than 1.4 μm,<br />
<strong>di</strong>ffraction effects become so significant to prevent the microlens from acting<br />
as a focusing element [1]. The research of <strong>di</strong>fferent focusing components is, at<br />
present, a challenge for a further size reduction of the image sensor pixel.<br />
Recently, planar lenses based on aperio<strong>di</strong>c nanoslit arrays on metal films<br />
allowed subwavelength focusing [2]. In this communication, we will report on<br />
the design and simulation of micron-sized planar lenses simply formed by<br />
circular holes in a metallic layer. We will show that the proposed <strong>di</strong>ffracting<br />
lenses with a lightpipe integrated in each pixel [3], make them suitable to<br />
replace the conventional microlenses in the CMOS image sensors and are<br />
compatible with their fabrication process.<br />
In Fig. 1 we show the CMOS image sensor model used for the simulations, the<br />
resulting pattern focusing and light confinement at �=633 nm and, finally, the<br />
normalized optical and cross-talk efficiency versus the pixel size.<br />
a) b) c)<br />
Figure 1 – a) The model of a 1.75 µm single pixel: gold layer is holed, 1.1µm in <strong>di</strong>ameter. b)<br />
The z-component of the Poyting vector at λ=633 nm. c) Normalized optical and cross-talk<br />
efficiency calculated for 4 pixel model versus pixel size at 1.75-1.4-1.2-1 µm.<br />
References<br />
[1] Y. Huo, C. C. Fesenmaier, and P. B. Catrysse, “Microlens performance limits in sub-2μm<br />
pixel CMOS image sensor”, Opt. Express, 18, 5861-5872, 2010.<br />
[2] L. Verslegers, P. B. Catrysse, Z. Yu, J. S. White, E. S. Barnard, M. L. Brongersma, and S.<br />
Fan, “Planar lenses based on nanoscale slit arrays in a metal film”, Nanoletters, 9, 235-<br />
238, 2009.<br />
[3] C. C. Fesenmaier, Y. Huo and P. B. Catrysse, “Optical confinement methods for<br />
continued scaling of CMOS image sensor pixels”, Opt. Express, 16, 20457-20470, 2008.<br />
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