Plasmonic Metasurface-Enabled Differential Photodetectors for Broadband Optical Polarization Characterization

Abstract

The polarization state of an optical field is central to applications in optical communications, imaging and data storage as well as furthering our understanding of biological and physical systems. Here we demonstrate two silicon photodetectors integrated with aluminum nanoantennas capable of distinguishing orthogonal states of either linearly or circularly polarised light with no additional filters. The localised plasmon resonances of the antennas lead to selective screening of the underlying silicon from light with a particular polarization state. The planar device, fully compatible with conventional CMOS fabrication methods, incorporates antennas sensitive to orthogonal states of polarization into two back-to-back Schottky photodetectors to produce a differential electrical signal that changes sign as the polarization of an incident optical beam changes from one basis state to the orthogonal state. The non-null response of the devices to each of the basis states expands the potential utility of the photodetectors while improving precision. Each device is wrapped into a spiral footprint to provide compatibility with the circular profile of conventional optical beams and has an overall diameter of 50 µm. The sensitivity of these devices is demonstrated experimentally 1 over a wavelength range from 500 to 800 nm establishing their potential for integration into a wide range of optical systems.

Fundamental limits of hot carrier injection from metal in nanoplasmonics

“…Let us now establish the efficiency of the hot electron injection, To estimate the transport efficiency we first introduce the mean free path of hot carriers, Note that this definition is different from the mean free path distribution in the Drude transport theory as it involves only EE scattering, since, as mentioned above, the collisions with phonons or defects do not affect the energy of hot carriers. Then we can introduce the "surface proximity factor" ( ) (20) where R is the distance to the surface and averaging is done over the solid angle. Obviously for small nanoparticles with dimension less than mfp L the proximity factor approaches unity.…”

“…It is the realization that loss in plasmonics is inevitable that has prompted a significant part of plasmonic community to re-examine the issue and shift the focus of their efforts from the futile battle to reduce the absorption in metals to the quest for creative use of that absorption [16,17], which in fact should not be thought of as an irretrievable loss but rather as the transfer of energy from plasmons first to the single particle excitations in metal (electron-hole pairs) and then to the lattice vibrations. If the absorbed energy can be recaptured on one of the stages before the equilibrium with the surroundings is achieved, it can be put into productive use as has been indeed demonstrated by a number of groups [6,[18][19][20]. The stage at which the absorbed energy can be captured with the least effort is obviously just after the energy has been transferred to the lattice (which in general is far less than a picosecond).…”

Hot carriers generated by plasmons: where are they generated and where do they go from there?

“…More recently the attention has been drawn to the all-together different class of applications, where the absorption is a positive, rather than deleterious, factor -such as plasmonic Schottky photo-detectors [6][7][8] and light harvesting [9,10]. In these applications the incoming photons excite surface plasmons, either propagating or localized, and the rapid decay of plasmons causes excitation of hot carriers which, once they reach the metal surface, can produce a photo-current in photodetectors [6][7][8], or initiate a chemical reaction in photo catalysis [11]. In order to understand the operation and evaluate the performance of these plasmon-assisted schemes, it is important not to know not only the rate with which plasmons decay but the distribution of energies and momentum of the hot carriers excited in the process.…”

“…In order to understand the operation and evaluate the performance of these plasmon-assisted schemes, it is important not to know not only the rate with which plasmons decay but the distribution of energies and momentum of the hot carriers excited in the process. As a general example consider a plasmonic Schottky detector [6][7][8] shown in Fig. 1.…”

Integrated on-chip silicon plasmonic four quadrant detector for near infrared light

“…14,15 On the other hand, SPPs also provide interesting electronic features such as light detection and electrical signal guiding. [16][17][18][19][20] These combinations of optical and electrical capabilities are inherent in the case of plasmons because the metal-dielectric interface is used.…”