Ultrathin Pyroelectric Photodetector with Integrated Polarization-Sensing Metasurface.

An abundance of metallic metasurfaces have been realized with miniscule, intricate features capable of tailored scattering, reflection, and absorption; however, high losses through heat limit their use in optoelectronics. Here, codesign of a detector and a polarization-sensing metasurface overcomes this challenge by utilizing the heat generation for integrated pyroelectric detection of the incoming light polarization. Using a nanogap metasurface with asymmetric metallic elements, polarization-sensitive photodetection exhibits high extinction ratios up to 19 for orthogonally polarized light and allows extraction of Stokes parameters with <12% deviation from theoretical values.

Shortwave Infrared Photodetection with oCVD Polythiophene.

Shortwave infrared (SWIR, λ = 1-3 µm) photodetectors typically use compound semiconductors that are fabricated using high-temperature epitaxial growth and require active cooling. New technologies that overcome these constraints are the focus of intensive current research. Herein, oxidative chemical vapor deposition (oCVD) is used for the first time to create a room temperature, vapor-phase deposited SWIR photoconductive detector with a unique tangled wire film morphology that detects nW-level photons emitted from a 500 °C cavity blackbody radiator-a rarity for polymer systems.

Contribution of Sub-Gap States to Broadband Infrared Response in Organic Bulk Heterojunctions.

This work studied a series of infrared detectors comprised of organic bulk heterojunctions to explain the origin of their broadband spectral response from the visible to the infrared spanning 1 to 8 μm and the transition from photonic to bolometric operation. Through comparisons of the detector current and the sub-bandgap density of states, the mid- and long-wave infrared response was attributed to charge trap-and-release processes that impact thermal charge generation and the activation energy of charge mobility. We further demonstrate how the sub-bandgap characteristics, mobility activation energy, and effective bandgap are key design parameters for controlling the device temperature coefficient of resistance, which reached up to -7%/K, better than other thin-film materials such as amorphous silicon and vanadium oxide.

Broadband infrared photodetection using a narrow bandgap conjugated polymer.

Photodetection spanning the short-, mid-, and long-wave infrared (SWIR-LWIR) underpins modern science and technology. Devices using state-of-the-art narrow bandgap semiconductors require complex manufacturing, high costs, and cooling requirements that remain prohibitive for many applications. We report high-performance infrared photodetection from a donor-acceptor conjugated polymer with broadband SWIR-LWIR operation.

Ultrafast pyroelectric photodetection with on-chip spectral filters.

Thermal detectors, such as bolometric, pyroelectric and thermoelectric devices, are uniquely capable of sensing incident radiation for any electromagnetic frequency; however, the response times of practical devices are typically on the millisecond scale. By integrating a plasmonic metasurface with an aluminium nitride pyroelectric thin film, we demonstrate spectrally selective, room-temperature pyroelectric detectors from 660-2,000 nm with an instrument-limited 1.7 ns full width at half maximum and 700 ps rise time.

Triplet sensitization in an anionic poly(phenyleneethynylene) conjugated polyelectrolyte by cationic iridium complexes.

We describe a systematic study of triplet sensitization in a poly(phenyleneethynylene) conjugated polyelectrolyte (CPE) in methanol solution by using a series of three cationic iridium complexes with varying triplet energy. The cationic iridium complexes bind to the anionic CPE by ion-pairing, leading to singlet state quenching of the polymer, and allowing for efficient back-transfer of triplet excitation energy to the polymer. Efficient (amplified quenching) of the polymer's fluorescence is observed for each iridium complex, with Stern-Volmer quenching constants in excess of 10(5) M(-1).

Off-Resonant Two-Photon Absorption Cross-Section Enhancement of an Organic Chromophore on Gold Nanorods.

Surface-plasmon-initiated interference effects of polyelectrolyte-coated gold nanorods on the two-photon absorption of an organic chromophore were investigated. With polyelectrolyte bearing gold nanorods of 2,4,6 and 8 layers, the role of the plasmonic fields as function of distance on such effects was examined. An unusual distance dependence was found: enhancements in the two-photon cross-section were at a minimum at an intermediate distance, then rose again at a further distance.

Plasmonic enhancement of the two photon absorption cross section of an organic chromophore using polyelectrolyte-coated gold nanorods.

The effect of plasmonic enhancement on the two-photon absorption cross section of organic chromophores attached to polyelectrolyte-coated gold nanorods was investigated. The magnitudes of such enhancements were confirmed using single and two photon excitations of the chromophore molecules bound to polyelectrolyte-coated gold nanorods. By synthesizing two-, four-, six-, and eight-polyelectrolyte layer coated nanorods of a particular aspect ratio, the distance dependence of the evanescent electromagnetic field on molecular two-photon absorption was observed.