Using resistive losses induced by optically excited surface plasmons has shown promise as a CMOS-compatible plasmonic light detector. Increased electron scattering introduced by surface plasmons in an applied current results in a measurable decrease in electrical conductance of a grating, allowing a purely electronic readout of surface plasmon excitation. Accordingly, because of its plasmonic nature, such a detector is dependent on both the wavelength and polarization of incident light with a response time limited by the surface plasmon lifetime. Our ultrafast measurements with electronic read-out indicate that the response time of this detector is on the order of 1ps. Thus such a detector would enable time-resolved biomedical applications such as real-time monitoring of protein structural dynamics for pharmacological applications and research.
Colloidal semiconductor nanoplatelets (NPLs) are quasi 2D-nanostructures that are grown and processed inexpensively using a solution based method and thus have recently attracted considerable attention. We observe two features in the photoluminescence spectrum, suggesting two possible recombination channels. Their intensity ratio varies with temperature and two distinct temperature regions are identified; a low temperature region (10K < T < 90K) and a high temperature region (90K < T < 200K). This ratio increases with increasing temperature, suggesting that one recombination channel involves holes that are weakly localized with a localization energy of 0.043meV. A possible origin of these localized states are energy-variations in the xy-plane of the nanoplatelet. The presence of positive photoluminescence circular polarization in the magnetically-doped core/multi-shell NPLs indicates a hole-dopant exchange interaction and therefore the incorporated magnetic Manganese ions act as a marker that determines the location of the localized hole states.1 Time-resolved measurements show two distinct timescales (τfast and τslow) that can be modeled using a rate equation model. We identify these timescales as closely related to the corresponding recombination times for the channels. The stronger hole localization of one of these channels leads to a decreased electron-hole wave function overlap and thus a decreased oscillator strength and an increased lifetime. We show that we can model and understand the magnetic interaction of doped 2D-colloidal nanoplatelets which opens a pathway to solution processable spin controllable light sources.
In this work, we take advantage of the resistive losses induced by plasmons excited at optical frequencies to design, fabricate and characterize a metal grating based CMOS-compatible light detector. A change of resistance is caused by increased electron scattering introduced by localized and delocalized surface plasmons in an applied current. We realize a spectral and polarization dependent detector that can be read out electronically. The optical response of the sensor can be tuned from the visible to IR regime by changing the geometry of the metal grating, which enables a variety of applications for an on-chip ultra-wideband plasmonic detector.
We studied the photoluminescence (PL)) from CdSe/CdMnS/CdS core/multi-shell colloidal nanoplatelets, a versatile platform to study the interplay of optical properties and nanomagnetism. The photoluminescence (PL) exhibits σ+ polarization in the applied magnetic field. Our measurement detects the presence of even a single magnetic monolayer shell. The PLL consists of a higher and a lower energy component; the latter exhibits a circular polarization peak. The time-resolved PL (trPL) shows a red shift as function of time delay. At early (later) times the trPL spectra coincide with the high (low) energy PL component. A model is proposed to interpret these results.