Photons Of Different Wavelengths Research Articles

Carrier dynamic identification enables wavelength and intensity sensitivity in perovskite photodetectors

Deciphering the composite information within a light field through a single photodetector, without optical and mechanical structures, is challenging. The difficulty lies in extracting multi-dimensional optical information from a single dimension of photocurrent. Emerging photodetectors based on information reconstruction have potential, yet they only extract information contained in the photoresponse current amplitude (responsivity matrix), neglecting the hidden information in response edges driven by carrier dynamics. Herein, by adjusting the thickness of the absorption layer and the interface electric field strength in the perovskite photodiode, we extend the transport and relaxation time of carriers excited by photons of different wavelengths, maximizing the spectrum richness of the edge waveform in the light-dark transition process. For the first time, without the need for extra optical and electrical components, the reconstruction of two-dimensional information of light intensity and wavelength has been achieved. With the integration of machine learning algorithms into waveform data analysis, a wide operation spectrum range of 350–750 nm is available with a 100% accuracy rate. The restoration error has been lowered to less than 0.1% for light intensity. This work offers valuable insights for advancing perovskite applications in areas such as wavelength identification and spectrum imaging.

ШЛЯХИ ПОБУДОВИ ЕНЕРГОЕФЕКТИВНИХ СВІТЛОДІОДНИХ СИСТЕМ ФІТООСВІТЛЕННЯ

Lighting of plant crops (phytolighting) realized on the basis of LEDs has revolutionized the field of indoor agriculture and cultivation of crops in closed controlled environments due to the possibility of optimizing the spectral composition and high energy efficiency. The use of specialised quasi-monochromatic radiation allows the activation of specific photomorphogenic, biochemical or physiological responses in plants, while LED radiation of a specific spectral composition (e.g. UV radiation) allows the control of plant pests and diseases. The literature review indicates that there is a species- and cultivar-specific response of plants to light radiation of a particular spectral composition and that this response varies with the stage of plant development, the intensity of illumination, the duration of plant development and specific interactions with the environment. Based on the developed recommendations for the spectral composition of radiation intended for plant illumination, the requirements for the spectral composition of light for phytolighting systems were determined. The efficiency of LEDs with different spectral compositions for plant illumination and the most energy efficient LEDs for use in phytolighting systems were determined. Special software was developed to determine the photon radiation efficiency and it was determined for a wide range of LED light sources. The LEDs studied had photon efficiencies ranging from 3.78 μmol/J (quasi-monochromatic blue LEDs) to 5.46 μmol/J (quasi- monochromatic red LEDs). White LEDs, depending on their colour rendering index, had a photon spectral efficiency in the range of 4.62-4.79 μmol/J. Some modern white LEDs with a high colour rendering index have a photon spectral efficiency close to that of phytolighting based on special quasi-monochromatic LEDs, but their efficiency, taking into account the weighting factor of the use of photons of different wavelengths for photosynthesis, is much lower.

Frequency-domain Hong-Ou-Mandel interference in cold atoms with induced atomic coherence

Hong-Ou-Mandel (HOM) interference with two independent photons of different wavelengths is a primary tool for controlled transfer of quantum information across a hybrid quantum network such as the quantum internet, in which the diverse material nodes operate at different resonant frequencies. The key challenge of realizing two-photon interference in the frequency domain is the need for linear frequency conversion between spectrally distinct photons, which, in contrast to frequency mixing in nonlinear optical processes, is free from multiphoton noise arising in strong laser fields. Here, we present a linear HOM scheme based on a lossless three-wave mixing between two photons of different frequencies in the laser-controlled tripod-type atoms, where the parametric interaction between photons is triggered by the induced coherence between two metastable states of the atoms [S. Petrosyan et al., Phys. Rev. A 105, 052606 (2022)]. We give the general derivation of the HOM effect and examine it for two single-pulse photons and in the important case of time-bin encoded single photons, which are well protected from decoherence in optical fibers. We show that two-photon coincidence measurements display the HOM-type ``dip and peak'' fringes according to the number of time bins in the incident photon state, allowing full recovery of the original quantum information. An essential feature of our scheme is the neutrality of the HOM effect implementation to the polarization indistinguishability of photons, which makes our model flexible for use in hybrid quantum networks.

Quantum frequency conversion with coherent transfer of time-bin encoding

Time-bin encoding of photons offers a robust kind of long-distance quantum communication over lossy channels. The diversity of material nodes in quantum networks operating at natural frequencies requires coherent frequency and wave-form conversion of information-carrying photons to provide an efficient quantum interface with optical fibers and various quantum memories, which has been extensively studied. However, the quantum frequency conversion with transfer of time-bin encoding between single photons of different wavelengths has not yet been explored. In this paper, we present a method for efficiently exchanging time-bin encoding in the conversion process between two photons propagating in cold tripod atoms driven by a strong laser field. The latter is designed to slow down photons and suppress their absorption due to electromagnetically induced transparency. Photons interact parametrically through modified atomic coherence, which is utilized also to achieve equal group velocities of photons. We demonstrate the ability of our model to generate entanglement between distant atoms that equally share the original quantum information stored in the ground-state polarization qubits of both atoms. The proposed method for frequency conversion based on modified atomic coherence is promising because it can simplify the implementation of reliable and high-speed quantum communication protocols based on single-photon entanglement.

Radiation Driven Chemistry in Biomolecules—is (V)UV Involved in the Bioactivity of Argon Jet Plasmas?

Cold physical plasmas, especially noble gas driven plasma jets, emit considerable amounts of ultraviolet radiation (UV). Given that a noble gas channel is present, even the energetic vacuum UV can reach the treated target. The relevance of UV radiation for antimicrobial effects is generally accepted. It remains to be clarified if this radiation is relevant for other biomedical application of plasmas, e.g., in wound care or cancer remediation. In this work, the role of (vacuum) ultraviolet radiation generated by the argon plasma jet kINPen for cysteine modifications was investigated in aqueous solutions and porcine skin. To differentiate the effects of photons of different wavelength and complete plasma discharge, a micro chamber equipped with a MgF2, Suprasil, or Borosilicate glass window was used. In liquid phase, plasma-derived VUV radiation was effective and led to the formation of cysteine oxidation products and molecule breakdown products, yielding sulfite, sulfate, and hydrogen sulfide. At the boundary layer, the impact of VUV photons led to water molecule photolysis and formation of hydroxyl radicals and hydrogen peroxide. In addition, photolytic cleavage of the weak carbon-sulfur bond initiated the formation of sulfur oxy ions. In the intact skin model, protein thiol modification was rare even if a VUV transparent MgF2 window was used. Presumably, the plasma-derived VUV radiation played a limited role since reactions at the boundary layer are less frequent and the dense biomolecules layers block it effectively, inhibiting significant penetration. This result further emphasizes the safety of physical plasmas in biomedical applications.

PWO based electromagnetic calorimetry to operate at a low temperature

The degradation of the optical transmittance under ionising radiation of the scintillation crystal in the scintillation spectral range leads to the losses of the light output, which results in the deterioration of the energy resolution and limits the operation time of the calorimeter made of the scintillator. This effect is especially prominent for calorimeters operating at a low temperature. The use of a lead tungstate scintillation crystal PbWO4 in calorimetry at a low temperature in the range from –20 to –45 °C provides a threefold increase in its scintillation yield, which causes a significant improvement in the energy resolution in the range up to 10 MeV. Keep on this feature is critically important for hadron spectroscopy. However, as the temperature of the PbWO4 crystal is lowered, the rate of spontaneous relaxation of colour centers created under ionising radiation significantly slows down, which shifts the dynamic level of the induced absorption towards a higher value under long-term irradiation of high-energy physics experiments. A comparison is made of the spontaneous relaxation of induced absorption in the spectral region of scintillations with stimulated relaxation upon irradiation of samples by infrared photons of different wavelengths. It is shown that the relaxation of colour centers can be accelerated up to one thousand times. Thus, recovery stimulation allows fast and efficient in situ recovery of the crystal optical transmittance either at beam-off periods or online at data acquisition. The application can substantially improve or extend the running period of the PWO based calorimeters at low temperatures by keeping the radiation damage at a tolerable level.

Two-colour interferometry and switching through optomechanical dark mode excitation

Efficient switching and routing of photons of different wavelengths is a requirement for realizing a quantum internet. Multimode optomechanical systems can solve this technological challenge and enable studies of fundamental science involving widely separated wavelengths that are inaccessible to single-mode optomechanical systems. To this end, we demonstrate interference between two optomechanically induced transparency processes in a diamond on-chip cavity. This system allows us to directly observe the dynamics of an optomechanical dark mode that interferes photons at different wavelengths via their mutual coupling to a common mechanical resonance. This dark mode does not transfer energy to the dissipative mechanical reservoir and is predicted to enable quantum information processing applications that are insensitive to mechanical decoherence. Control of the dark mode is also utilized to demonstrate all-optical, two-colour switching and interference with light separated by over 5 THz in frequency.

Anti-Hermitian photodetector facilitating efficient subwavelength photon sorting

The ability to split an incident light beam into separate wavelength bands is central to a diverse set of optical applications, including imaging, biosensing, communication, photocatalysis, and photovoltaics. Entirely new opportunities are currently emerging with the recently demonstrated possibility to spectrally split light at a subwavelength scale with optical antennas. Unfortunately, such small structures offer limited spectral control and are hard to exploit in optoelectronic devices. Here, we overcome both challenges and demonstrate how within a single-layer metafilm one can laterally sort photons of different wavelengths below the free-space diffraction limit and extract a useful photocurrent. This chipscale demonstration of anti-Hermitian coupling between resonant photodetector elements also facilitates near-unity photon-sorting efficiencies, near-unity absorption, and a narrow spectral response (∼ 30 nm) for the different wavelength channels. This work opens up entirely new design paradigms for image sensors and energy harvesting systems in which the active elements both sort and detect photons.

Modeling and simulation of the influence of fractions of blue and red light on the growth of the microalga Scenedesmus quadricauda

Lighting conditions of microalgal cultures have great impact on the biomass composition and on the efficiency of energy usage. In this work, the green microalgae Scenedesmus quadricauda was grown in a laboratory scale photobioreactor irradiated with blue and red LEDs in different proportions. In order to ensure that the observed effects are caused by the light spectral composition and not by its intensity, different arrangements of LEDs were built so that they emit the same total number of photons per unit time and per unit volume of culture. The interaction between suspended algal cells and the radiation field within the culture has been modeled.The impact of the light distribution within the cultures on the growth rate rx, as well as on the amount of chlorophylls per unit biomass and on the efficiency of usage of photons, has been assessed. The effects of the alternative use of red and blue light were analyzed in previous studies [17,41]. In this work, experiments using irradiation light consisting in mixtures of these two colors in different proportions were carried out. From these experiments it can be concluded that the efficiency of light usage for the same intensity of light, is not the result of the independent contribution of each fraction of photons of different wavelength reaching the reactor, but instead these fractions interfere with each other in the absorption process.

Doubly Dressed Bosons: Exciton Polaritons in a Strong Terahertz Field.

We demonstrate the existence of a novel quasiparticle, an exciton in a semiconductor doubly dressed with two photons of different wavelengths: a near infrared cavity photon and terahertz (THz) photon, with the THz coupling strength approaching the ultrastrong coupling regime. This quasiparticle is composed of three different bosons, being a mixture of a matter-light quasiparticle. Our observations are confirmed by a detailed theoretical analysis, treating quantum mechanically all three bosonic fields. The doubly dressed quasiparticles retain the bosonic nature of their constituents, but their internal quantum structure strongly depends on the intensity of the applied terahertz field.

Cooling of isolated anthracene cations probed with photons of different wavelengths in the Mini-Ring.

We report on a direct measurement of the Internal Energy Distribution (IED) shift rate of an initially hot polycyclic aromatic hydrocarbon (PAH) molecular ensemble, anthracene cations (C14H10+). The ions were produced in an electron cyclotron resonance (ECR) ion source and stored in an electrostatic ion storage ring, the Mini-Ring. Laser pulses of two wavelengths were sent successively to merge the stored ion bunch at different storage times to enhance the neutral fragment yield due to fast laser induced dissociation. Using this technique, we have been able to determine directly the energy shift rate of the IED, without involving any theoretical simulation or any assumption on dissociation rates, cooling rates, or the initial IED. Theoretical energy shift rates have been estimated from the evolution of simulated IEDs by taking into account the effects of the unimolecular dissociation and two radiative decay mechanisms: the Poincaré fluorescence and the infrared vibrational emission. The comparison between the experimental results and the model provides new evidence of the important role of the Poincaré fluorescence in the overall cooling process of anthracene cations. Although in the short time range the commonly accepted intuition says that the cooling would result mostly from the dissociation of the hottest ions (depletion cooling), we demonstrate that the Poincaré fluorescence is the dominant contribution (about 85%) to the net cooling effect.

Chromatic Mechanical Response in 2-D Layered Transition Metal Dichalcogenide (TMDs) based Nanocomposites.

The ability to convert photons of different wavelengths directly into mechanical motion is of significant interest in many energy conversion and reconfigurable technologies. Here, using few layer 2H-MoS2 nanosheets, layer by layer process of nanocomposite fabrication, and strain engineering, we demonstrate a reversible and chromatic mechanical response in MoS2-nanocomposites between 405 nm to 808 nm with large stress release. The chromatic mechanical response originates from the d orbitals and is related to the strength of the direct exciton resonance A and B of the few layer 2H-MoS2 affecting optical absorption and subsequent mechanical response of the nanocomposite. Applying uniaxial tensile strains to the semiconducting few-layer 2H-MoS2 crystals in the nanocomposite resulted in spatially varying energy levels inside the nanocomposite that enhanced the broadband optical absorption up to 2.3 eV and subsequent mechanical response. The unique photomechanical response in 2H-MoS2 based nanocomposites is a result of the rich d electron physics not available to nanocomposites based on sp bonded graphene and carbon nanotubes, as well as nanocomposite based on metallic nanoparticles. The reversible strain dependent optical absorption suggest applications in broad range of energy conversion technologies that is not achievable using conventional thin film semiconductors.

Broadband, sensitive and spectrally distinctive SnS2 nanosheet/PbS colloidal quantum dot hybrid photodetector.

Photodetectors convert photons into current or voltage outputs and are thus widely used for spectroscopy, imaging and sensing. Traditional photodetectors generally show a consistent-polarity response to incident photons within their broadband responsive spectrum. Here we introduced a new type of photodetector employing SnS2 nanosheets sensitized with PbS colloidal quantum dots (CQDs) that are not only sensitive (~105 A W−1) and broadband (300–1000 nm) but also spectrally distinctive, that is, show distinctive (positive or negative) photoresponse toward incident photons of different wavelengths. A careful mechanism study revealed illumination-modulated Schottky contacts between SnS2 nanosheets and Au electrodes, altering the photoresponse polarity toward incident photons of different wavelengths. Finally, we applied our SnS2 nanosheet/PbS CQDs hybrid photodetector to differentiate the color temperature of emission from a series of white light-emitting diodes (LEDs), showcasing the unique application of our novel photodetectors.

Frequency conversion in silicon in the single photon regime.

Quantum communication networks require single photon frequency converters, whether to shift photons between wavelength channels, to shift photons to the operating wavelength of a quantum memory, or to shift photons of different wavelengths to be of the same wavelength, to enable a quantum interference. Here, we demonstrate frequency conversion of laser pulses attenuated to the single photon regime in an integrated silicon-on-insulator device using four-wave mixing Bragg scattering, with conversion efficiencies of up to 12%, or 32% after correcting for nonlinear loss created by the pump lasers. The frequency shift can be conveniently chosen by tuning of the pump frequencies. We demonstrate that such frequency conversion enables interference between photons at different frequencies.

Shifting wavelengths of ultraweak photon emissions from dying melanoma cells: their chemical enhancement and blocking are predicted by Cosic’s theory of resonant recognition model for macromolecules

During the first 24 h after removal from incubation, melanoma cells in culture displayed reliable increases in emissions of photons of specific wavelengths during discrete portions of this interval. Applications of specific filters revealed marked and protracted increases in infrared (950 nm) photons about 7 h after removal followed 3 h later by marked and protracted increases in near ultraviolet (370 nm) photon emissions. Specific wavelengths within the visible (400 to 800 nm) peaked 12 to 24 h later. Specific activators or inhibitors for specific wavelengths based upon Cosic's resonant recognition model elicited either enhancement or diminishment of photons at the specific wavelength as predicted. Inhibitors or activators predicted for other wavelengths, even within 10 nm, were less or not effective. There is now evidence for quantitative coupling between the wavelength of photon emissions and intrinsic cellular chemistry. The results are consistent with initial activation of signaling molecules associated with infrared followed about 3 h later by growth and protein-structural factors associated with ultraviolet. The greater-than-expected photon counts compared with raw measures through the various filters, which also function as reflective material to other photons, suggest that photons of different wavelengths might be self-stimulatory and could play a significant role in cell-to-cell communication.

Quantum dots as biophotonics tools.

This chapter provides a short review of quantum dots (QDs) physics, applications, and perspectives. The main advantage of QDs over bulk semiconductors is the fact that the size became a control parameter to tailor the optical properties of new materials. Size changes the confinement energy which alters the optical properties of the material, such as absorption, refractive index, and emission bands. Therefore, by using QDs one can make several kinds of optical devices. One of these devices transforms electrons into photons to apply them as active optical components in illumination and displays. Other devices enable the transformation of photons into electrons to produce QDs solar cells or photodetectors. At the biomedical interface, the application of QDs, which is the most important aspect in this book, is based on fluorescence, which essentially transforms photons into photons of different wavelengths. This chapter introduces important parameters for QDs' biophotonic applications such as photostability, excitation and emission profiles, and quantum efficiency. We also present the perspectives for the use of QDs in fluorescence lifetime imaging (FLIM) and Förster resonance energy transfer (FRET), so useful in modern microscopy, and how to take advantage of the usually unwanted blinking effect to perform super-resolution microscopy.

DIFFERENCES OF LEPTONIC AND HADRONIC RADIATION PRODUCTION IN FLARING BLAZARS

In order to distinguish the leptonic from the hadronic origin of the non-thermal emission of a flaring blazar, we present a semi-analytical model that describes the temporal development of the emergent particles (i.e., photons and neutrinos) based on their leptonic and hadronic origins, respectively. The approach starts with the transport equation of the injected relativistic particles and takes spatial diffusion and continuous energy losses into account. On the one hand, a relativistic electron pick-up is considered, which leads to synchrotron, as well as external Compton emission; and on the other hand, a relativistic proton pick-up, which results in high-energy photons and neutrinos by inelastic proton-proton collisions. The temporal development of the emergent photon and neutrino intensities of blazar flares in hadronic and leptonic interaction scenarios are calculated, given useful predictions of flare durations and time lags between photons of different wavelength and high-energy neutrinos.

Time lags of flaring AGN

In order to distinguish the leptonic from the hadronic origin of the non-thermal emission of a flaring AGN we present a semi-analytical model that describes the temporal development of the emergent particles (i.e. photons and neutrinos) based on their leptonic and hadronic origin respectively. The approach starts with the transport equation of the injected relativistic particles and takes spatial diffusion and continuous energy losses into account. On the one hand, a relativistic electron pick-up is considered, that leads to synchrotron, as well as external Compton emission and on the other hand, a relativistic proton pick-up, which results in high energy photons and neutrinos by inelastic proton-proton collisions. The paper ends up in the temporal development of the emergent photon and neutrino intensities of AGN flares in hadronic and leptonic interaction scenarios and gives useful predictions of flare durations and time lags between photons of different wavelength and high energy neutrinos.

SU‐C‐211‐05: Improved Target Localization with Integrated X‐Ray/bioluminescent Tomography

Purpose: Bioluminescence tomography (BLT) is a promising approach to guide focal irradiation of pre‐palpable tumors in small animals, but is limited in resolution. In this study, we investigate the use of x‐ray and diffuse optical tomography tomography to provide spatial and optical information about the object to improve BLT reconstruction. Methods: In a 3‐step approach, x‐ray CBCT is used first to provide the anatomic spatial information about the object. Secondly, photons of different wavelengths are transmitted through the object for detection by a CCD camera. The optical properties of the anatomic regions are then found by solutions of the diffuse optical tomography problem. In the final step, the anatomic and optical “priors” are employed in BLT reconstruction, where optical filters are used again to extract the multi‐spectral information required to derive the position and power of the internal source. The approach was tested in an experimental setup where a 1.5 mm diameter (dia) optical fiber light source was inserted at 5 different lateral positions in a 12 mm dia optical heterogeneity within a 25 mm dia cylindrical tissue‐mimicking phantom. The reconstructed positions and powers were compared with the known inputs. Results: The average error in locating the source centroid was 0.13 mm, range 0.3 mm to 0 mm. The average error in source power estimations was 9%, range 14% to −1%. The results are an improvement over commercial systems that typically have an average localization uncertainty of 1 mm and error in power estimation of more than 20%. Conclusions: The spatial and spectral prior information provided by x‐ray CT and diffuse optical tomography improves the accuracy of BLT. Integrated x‐ray/BL tomographic capability on board new small animal radiation research systems can contribute significantly to accurate biological targeting in realistic animal models.J Wong has a sponsored research agreement with Xstrahl Ltd on small animal radiation research.

Glycerol-Bonded 3C-SiC Nanocrystal Solid Films Exhibiting Broad and Stable Violet to Blue-Green Emission

We have produced glycerol-bonded 3C-SiC nanocrystal (NC) films, which when excited by photons of different wavelengths, produce strong and tunable violet to blue-green (360-540 nm) emission as a result of the quantum confinement effects rendered by the 3C-SiC NCs. The emission is so intense that the emission spots are visible to the naked eyes. The light emission is very stable and even after storing in air for more than six months, no intensity degradation can be observed. X-ray photoelectron spectroscopy and absorption fine structure measurements indicate that the Si-terminated NC surfaces are completely bonded to glycerol molecules. Calculations of geometry optimization and electron structures based on the density functional theory for 3C-SiC NCs with attached glycerol molecules show that these molecules are bonded on the NCs causing strong surface structural change, while the isolated levels in the conduction band of the bare 3C-SiC NCs are replaced with quasi-continuous bands that provide continuous tunability of the emitted light by changing the frequencies of exciting laser. As an application, we demonstrate the potential of using 3C-SiC NCs to fabricate full-color emitting solid films by incorporating porous silicon.