Fundamental Scaling Laws in Nanophotonics

Abstract

The success of information technology has clearly demonstrated that miniaturization often leads to unprecedented performance, and unanticipated applications. This hypothesis of “smaller-is-better” has motivated optical engineers to build various nanophotonic devices, although an understanding leading to fundamental scaling behavior for this new class of devices is missing. Here we analyze scaling laws for optoelectronic devices operating at micro and nanometer length-scale. We show that optoelectronic device performance scales non-monotonically with device length due to the various device tradeoffs, and analyze how both optical and electrical constrains influence device power consumption and operating speed. Specifically, we investigate the direct influence of scaling on the performance of four classes of photonic devices, namely laser sources, electro-optic modulators, photodetectors, and all-optical switches based on three types of optical resonators; microring, Fabry-Perot cavity, and plasmonic metal nanoparticle. Results show that while microrings and Fabry-Perot cavities can outperform plasmonic cavities at larger length-scales, they stop working when the device length drops below 100 nanometers, due to insufficient functionality such as feedback (laser), index-modulation (modulator), absorption (detector) or field density (optical switch). Our results provide a detailed understanding of the limits of nanophotonics, towards establishing an opto-electronics roadmap, akin to the International Technology Roadmap for Semiconductors.

Active material, optical mode and cavity impact on nanoscale electro-optic modulation performance

“…The effect of a cavity for a modulator can be compared to a linear device (e.g. MZ, EAM), and one can reach the following qualitative results: the cavity (i) allows for more compact device designs, (ii) increases modulation sensitivity, (iii) however, limits modulation speeds and spectral bandwidth, and (iv) allows for a reduction in power consumption [48]. Next, we discuss some of these qualitatively.…”

“…We note that broader gap dimensions lead to higher order modes, lower optical confinement, and hence lower ER. This value (20 nm) can be understood from two aspects both relating to the fact that metallic confinement beyond 20 nm is not favorable: (a) the skin depth of plasmons at telecom wavelengths is about 20-30 nm, and (b) the Purcell factor reduces dramatically beyond 10 nm small plasmonic cavities due to high losses and field leakage [48]. Our results indeed confirm a modal confinement to the gap and a high field strength (peak |E| 2 ), which is 4600 times higher compared to the bulk case ( Figure 2H′).…”

“…light absorption in the cavity, and α pen denotes the metallic loss due to field penetration into the mirrors. κ D and κ m are the extinction coefficients of dielectric and metal materials, respectively, δ s is the penetration or skin depth of the metal at a corresponding frequency of the trapped light at which the field magnitude drops to 1/e of the surface value and is given by , and ε 0 is the vacuum permittivity [48]. κ m is high for metals, i.e.…”

“…For the FP cavity an established formula for analytical manipulations exists to aid our approach [48].…”

Introduction

“…Another take on the scaling rules for optical switching with nanophotonics and generally concentrating on resonant nanophotonic structures can be found in [7].…”