Optical Remote Control Research Articles

Toward laser-induced tuning of plasmonic response in high aspect ratio gold nanostructures

Abstract High aspect-ratio gold nanostructures sustain Fabry–Perot-like surface plasmon responses from infrared to visible light energies. We show that some resonances can be tuned by means of laser irradiation, where low energy modes stay unperturbed. After laser irradiation, gold nanowires’ tips are transformed into nanoparticles of various sizes joint to gold nanowires, producing high aspect-ratio half-dumbbells and dumbbells structures. The plasmonic behaviour of both the nanowires and the newly created nanostructures has been characterised by in-depth monochromated electron energy loss spectroscopy (EELS) developed in a transmission electron microscope (TEM) and state-of-the-art discrete dipole approximation (DDA) calculations. All these analyses serve as experimental proof of the selective tuning (or robustness) of the plasmonic modes of the nanostructures in a specific spectral range, which is of critical interest regarding applications for sensing devices, nano-sources or nanophotonic waveguide, as well as optical remote control.

Observation of giant persistent photoconductivity on vanadium dioxide thin film device

We report a giant persistent photoconductivity (GPPC) phenomenon in VO2 film device prepared on corning glass substrate. With a single pulse laser irradiation onto the device at bias voltages of 7 V and 8 V, the VO2 film makes an insulator-to-metal transition with a sharp increase of photo current. The photo current remained at a highly conductive state for long period, e.g. the photo current for VO2 device was decreased only ~1% in one day. The GPPC was found within the limit of critical voltages of the hysteresis loop in voltage vs current curve of the device. High speed time-current measurements on the device with a 20 ms single pulse laser irradiation revealed that the onset of abrupt photo current occurs in less than 1 ms time scale. The GPPC in VO2 device can contribute in realizing ultrafast optical remote control of advanced electronic devices i.e. optical memories, displays, and remote ultrafast switching devices.

Ultrasensitive graphene position-sensitive detector induced by synergistic effects of charge injection and interfacial gating

Abstract Position-sensitive detectors (PSDs) are essential components to the realization of displacement and vibration detection, optical remote control, robot vision, etc. The light sensitivity of PSDs is a crucial parameter, which determines the operating range or detection accuracy of the measurement systems. Here, we devise an ultrasensitive PSD based on graphene/Si hybrid structure by using the synergistic effect of charge injection and interfacial gating. Photogenerated carriers in Si are separated by the built-in electric field at the surface. Holes diffuse laterally in inversion layer and then inject into graphene to form photoresponse. Meanwhile, the electrons in bulk Si that move to the area under graphene cause a gating effect, thus introducing a high gain. With the benefit of synergistic effect, the detection limit power of our device can be pushed to pW level, which is reduced by two orders of magnitude compared to previously reported graphene based PSD. Furthermore, even for infrared light of 1064 nm, the PSD still retains position sensitivity to 1 nW weak light, as well as fast response speed at the μs level. This work provides the potential of graphene as a promising material for ultraweak light position sensitive detection.

Photothermal enhanced enzymatic activity of lipase covalently immobilized on functionalized Ti3C2TX nanosheets

The rational design of new supports is critical for modern enzyme immobilization for advanced biocatalysis. Meanwhile, utilizing the photothermal effect of the support to achieve optical remote control of enzymatic activity remains a huge challenge. MXene, owing to its rich surface functional groups, biological compatibility and excellent photothermal effect, is a promising support material to satisfy the above requirements. Herein, a facile method to covalently bond lipase onto the surface of Ti3C2TX nanosheets through the coordination interaction with aminosilane ligand spacers is reported. The enzymatic activities of immobilized lipase are tuned based on the photothermal properties of Ti3C2TX nanosheets by exposure to near-infrared (NIR) light. The immobilized lipase shows an enhanced catalytic activity for the hydrolysis of p-nitrophenylpalmitate (pNPP) after NIR irradiation. In addition, immobilized lipase exhibits good pH, thermal stability and reusability, which are important in practical uses of enzymes.

Optical pressure control with aperiodic nanostructured material

The electromagnetic force on matter depends on both the geometry and the material properties, and for a contiguous material with a periodic boundary condition, the pressure is a useful metric. We present a statistical method with example results that allows the evaluation of pressure in relation to a nanostructured material arrangement formed by populating pixels within a region one wavelength on a side. The two example materials considered are gold and silicon, both in a free-space background. We find that both the magnitude of the pressure and the direction can be regulated, depending on the geometry, and these effects are related to the specifics of the internal structure resonances. Control of positive and negative pressure can be understood as being due to the total field, a superposition of the incident and scattered fields, where the structure regulates the local scattered field and hence the pressure through an integral of the resulting force density. The statistical analysis provides physical insight into how to constrain the design framework for applications. The application space includes biophysics, where information is obtained about biomolecules from force and torque measurements, cavity optomechanics related to basic science and sensing, and optical remote control and actuation, where regulation of the magnitude and direction and the possibility of materials with multiple functionalities provide new opportunities.

Optical remote control of a single charge qubit

Both the electron transport-based qubits, implemented through double quantum dots, and the sources of indistinguishable single-photons like self-assembled quantum dots are strong candidates for the implementation of quantum technologies, such as quantum computers and quantum repeaters. Here, we demonstrate a reliable way of coupling these two types of qubits, uncovering the possibility of controlling and reading out the population of the double quantum dot via optical excitation. It is also showed that, in spite of the decoherence mechanisms affecting the qubits, the entanglement between them is achievable and, consequently, the implementation of the suggested system in quantum technologies is feasible.

Self-powered wireless optical transmission of mechanical agitation signals

The ubiquitous sensors have accelerated the realization of Internet of Things (IoT) but also raised challenges to the current overcrowding radio frequency (RF) based communications. The optical wireless communication (OWC) that utilizes the wide optic bandwidth can well solve the spectrum crisis and is an appealing complementary solution to the IoT applications. However, the additional direct current (DC) power supply and complicated modulating and power management circuits may limit the large-scale deployment of OWC systems. In this paper, by integrating with triboelectric nanogenerators (TENGs), the light-emitting diode (LED) could be directly transformed into a wireless transmitter that conveys the information associated with mechanical stimuli without additional power supply. With the customized TENG devices and the help of advanced image processing and machine learning techniques, three demonstrations with functions of optical remote control, pressure sensing, and security authentication, were demonstrated. The concept and results in this paper may greatly broaden the application of IoT through the integration of OWC and TENG.

Optical Control of Endogenous Proteins with a Photoswitchable Conditional Subunit Reveals a Role for TREK1 in GABAB Signaling

Selective ligands are lacking for many neuronal signaling proteins. Photoswitched tethered ligands (PTLs) have enabled fast and reversible control of specific proteins containing a PTL anchoring site and have been used to remote control overexpressed proteins. We report here a scheme for optical remote control of native proteins usinga "photoswitchable conditional subunit" (PCS), which contains the PTL anchoring site as well as a mutation that prevents it from reaching the plasma membrane. In cells lacking native subunits for the protein, the PCS remains nonfunctional internally. However, in cells expressing native subunits, the native subunit and PCS coassemble, traffic to the plasma membrane, and place the native protein under optical control provided by the coassembled PCS. We apply this approach to the TREK1 potassium channel, which lacks selective, reversible blockers. We find that TREK1, typically considered to be a leak channel, contributes to the hippocampal GABA(B) response.

Optically driven fluid flow along arbitrary microscale patterns using thermoviscous expansion

We show how fluid can be moved by a laser scanning microscope. Selected parts of a fluid film are pumped along the path of a moving warm spot which is generated by the repetitive motion of an infrared laser focus. With this technique, we remotely drive arbitrary two-dimensional fluid flow patterns with a resolution of 2μm. Pump speeds of 150μm∕s are reached in water with a maximal temperature increase in the local spot of 10K. Various experiments confirm that the fluid motion results from the dynamic thermal expansion in a gradient of viscosity. The viscosity in the spot is reduced by its enhanced temperature. This leads to a broken symmetry between thermal expansion and thermal contraction in the front and the wake of the spot. As result the fluid moves opposite to the spot direction due to both the asymmetric thermal expansion in the spot front and the asymmetric thermal contraction in its wake. We derive an analytical expression for the fluid speed from the Navier–Stokes equations. Its predictions are experimentally confirmed without fitting parameters under a number of different conditions. In water, this nonlinearity leads to a fluid step of <100nm for each passage of the spot. Since the spot movement can be repeated in the kilohertz regime, fluid speeds can exceed 100μm∕s. Using this technique, we pump nanoparticles over millimeters through a gel. An all-optical creation of a dilution series of DNA and biomolecules by aliquotation and mixing is demonstrated for fluids sandwiched between untreated and unstructured, disposable microscope cover slips. The shown optical remote control of fluid flow expands the microfluidic paradigm into previously inaccessible regimes of tiny volumes, closed flow paths, fast switching between flow patterns, and remote fluid control under extreme fluid conditions.

Controlling neural circuits with light

Two light-sensitive proteins from unicellular organisms have been harnessed to rapidly activate or silence neurons. This optical remote control allows precise, millisecond control of neural circuits.

Remote optically-tunable transimpedance amplifiers for quantum well diodes

In a previous paper [1] we discussed the advantages in using linear optical transmission systems based on quantum well diodes in modern high energy physics experiments. In this paper, after a short summary of the quantum well theory, the electronics section of the above optical transmission system is presented. In particular the basic configuration of a transimpedance amplifier and the arrangement of an optical remote control system for the amplifier gain and bandwidth tuning are discussed.