Resonance Peak Wavelength Research Articles

High-Q Fabry⁻Pérot Micro-Cavities for High-Sensitivity Volume Refractometry.

This work reports a novel structure for a Fabry–Pérot micro cavity that combines the highest reported quality factor for an on-chip Fabry–Pérot resonator that exceeds 9800, and a very high sensitivity for an on-chip volume refractometer based on a Fabry–Pérot cavity that is about 1000 nm/refractive index unit (RIU). The structure consists of two cylindrical Bragg micromirrors that achieve confinement of the Gaussian beam in the plan parallel to the chip substrate, while for the perpendicular plan, external fiber rod lenses (FRLs) are placed in the optical path of the input and the output of the cavity. This novel structure overcomes number of the drawbacks presented in previous designs. The analyte is passed between the mirrors, enabling its detection from the resonance peak wavelengths of the transmission spectra. Mixtures of ethanol and deionized (DI)-water with different ratios are used as analytes with different refractive indices to exploit the device as a micro-opto-fluidic refractometer. The design criteria are detailed and the modeling is based on Gaussian-optics equations, which depicts a scenario closer to reality than the usually used ray-optics modeling.

Single nanoparticle trapping based on on-chip nanoslotted nanobeam cavities

Optical trapping techniques are of great interest since they have the advantage of enabling the direct handling of nanoparticles. Among various optical trapping systems, photonic crystal nanobeam cavities have attracted great attention for integrated on-chip trapping and manipulation. However, optical trapping with high efficiency and low input power is still a big challenge in nanobeam cavities because most of the light energy is confined within the solid dielectric region. To this end, by incorporating a nanoslotted structure into an ultracompact one-dimensional photonic crystal nanobeam cavity structure, we design a promising on-chip device with ultralarge trapping potential depth to enhance the optical trapping characteristic of the cavity. In this work, we first provide a systematic analysis of the optical trapping force for an airborne polystyrene (PS) nanoparticle trapped in a cavity model. Then, to validate the theoretical analysis, the numerical simulation proof is demonstrated in detail by using the three-dimensional finite element method. For trapping a PS nanoparticle of 10 nm radius within the air-slot, a maximum trapping force as high as 8.28 nN/mW and a depth of trapping potential as large as 1.15×105 kBT mW−1 are obtained, where kB is the Boltzmann constant and T is the system temperature. We estimate a lateral trapping stiffness of 167.17 pN·nm−1· mW−1 for a 10 nm radius PS nanoparticle along the cavity x-axis, more than two orders of magnitude higher than previously demonstrated on-chip, near field traps. Moreover, the threshold power for stable trapping as low as 0.087 μW is achieved. In addition, trapping of a single 25 nm radius PS nanoparticle causes a 0.6 nm redshift in peak wavelength. Thus, the proposed cavity device can be used to detect single nanoparticle trapping by monitoring the resonant peak wavelength shift. We believe that the architecture with features of an ultracompact footprint, high integrability with optical waveguides/circuits, and efficient trapping demonstrated here will provide a promising candidate for developing a lab-on-a-chip device with versatile functionalities.

Influence of intra-cavity loss on transmission characteristics of fiber Bragg grating Fabry–Perot cavity**Project supported by the National Natural Science Foundation of China (Grant Nos. 61405212, 61377062, 61405218, and 61775225) and Scientific Innovation Fund of Chinese Academy of Sciences (Grant No. CXJJ-17S010).

A theoretical model of the fiber Bragg grating Fabry–Perot (FBG-FP) transmission spectrum considering loss of FBG and intra-cavity fiber is presented. Several types of FBG-FPs are inscribed experimentally, and their spectra are measured. The results confirm that weak intra-cavity loss is enhanced at the resonance transmission peak, that is, loss of transmission peaks is observably larger than other wavelengths. For FBG-FPs with multi resonance peaks, when the resonance peak wavelength is closer to the Bragg wavelength, the more significant loss effect of resonance transmission peak is exhibited. The measured spectra are fitted with the presented theoretical model. The fitted coefficient of determinations are near 1, which proves the validity of the theoretical model. This study can be applied to measure FBG loss more accurately, without a reference light. It can play an important role in FBG and FBG-FP writing process optimization and application parameter optimization.

Photonic Crystal Surface Emitting Lasers With Quantum Dot Active Region

GaAs-based InAs/InGaAs/GaAs quantum dot (QD) photonic crystal (PC) surface emitting lasers of 1.3 μm wavelength range are fabricated and room-temperature lasing emissions by optical pumping are demonstrated for the first time. Laser devices are characterized in terms of PC parameters and temperature-dependent measurements are also carried out. The impact of wavelength detuning between PC resonant wavelength and QD gain peak is manifested in the experiments. Moreover, simplified simulation reveals that etched PC depth plays an even more critical role in active region of QD compared to that of quantum well.

Investigation of plasmonic effects on the metal nanoparticle arrays for biosensor applications

Surface plasmon resonance (SPR) on the near field intensity of a two-dimensional (2-D) periodic arrays of bowtie-shape metal nanoparticle (MNP) pairs using the 3-D finite element method (FEM) for biosensor applications are investigated. The peak resonance wavelength can be shifted to red as the filling core media in bowtie-shape MNP pairs have been changed. The tunable and highly sensitive SPR modes are observed due to the hybridization SPR effects. Simulation results show that the peak resonance wavelength (λres) can be spread in the full wavelength range of 300-1600 nm when the tip edges and different filling media in structure are taken into account. The highly sensitive optical performances give us a qualitative idea of the geometrical and material properties of the periodic array of bowtie-shape MNP pairs on SPRs that can be as a promising candidate for plasmonic biosensor applications.

Plasmonic Sensing of Oncoproteins without Resonance Shift Using 3D Periodic Nanocavity in Nanocup Arrays

A sensor design and sensing method based on plasmonic–photonic interactions that occur when a nanocavity array is embedded in a 3D tapered nanocup plasmonic substrate are reported. This device enables highly sensitive detection of refractive index changes based on changes to the transmission peak intensity without shift in the resonance wavelength. Unlike conventional plasmonic sensors, there is a consistent and selective change in the transmission intensity at the resonance peak wavelength with no spectral shift. In addition, there are wavelength ranges that show no intensity change, which can be used as reference regions. The fabrication and characterization of the plasmonic nanocavity sensor are described and also advanced biosensing is demonstrated. Simulations are carried out to better understand the plasmon–photonic coupling mechanism. This nanocavity plasmonic sensor design has a limit of detection of 1 ng mL−1 (5 × 10−12m) for the cancer biomarker carcinoembryonic antigen (CEA), which is a significant improvement over current surface plasmon resonance systems, and a dynamic range that is clinically relevant for human CEA levels.

Plasmonic detection of mercury via amalgam formation on surface-immobilized single Au nanorods

Au nanorods were used as plasmonic transducers for investigation of mercury detection through a mechanism of amalgam formation at the nanorod surfaces. Marked scattering color transitions and associated blue shifts of the surface plasmon resonance peak wavelengths (λmax) were measured in individual nanorods by darkfield microscopy upon chemical reduction of Hg(II). Such changes were related to compositional changes occurring as a result of Hg–Au amalgam formation as well as morphological changes in the nanorods’ aspect ratios. The plot of λmax shifts vs. Hg(II) concentration showed a linear response in the 10–100 nM concentration range. The sensitivity of the system was ascribed to the narrow width of single nanorod scattering spectra, which allowed accurate determination of peak shifts. The system displayed good selectivity as the optical response obtained for mercury was one order of magnitude higher than the response obtained with competitor ions. Analysis of mercury content in river and tap water were also performed and highlighted both the potential and limitation of the developed method for real sensing applications.

Manipulating near field enhancement and optical spectrum in a pair-array of the cavity resonance based plasmonic nanoantennas

A 2D periodic pair-array of cavity resonance based (CRB) plasmonic nanoantennas (PNAs) on the tailoring near field enhancement and optical spectrum of surface plasmon resonance (SPR) modes is numerically investigated by using the finite element method. The CRBPNAs consist of a single cavity or double cavities in each antenna arm. Detailed physical explanations of the simulation results and consistent dependencies of the SPR features on the structural and material parameters of CRBPNAs are presented. Compared to the solid case of counterpart, the proposed CRBPNAs display outstanding SPR characteristics and tune the peak resonance wavelength by varying the outline thickness and the cavity material. In addition, the field enhancement and optical spectrum can be precisely controlled by cavity material and outline thickness in the broad band of ultraviolet, visible and near-infrared, resulting in increased sensitivity and supporting resonances with gaps and cavity surface plasmom as well as the high value of Q factors. We interpret the optical properties of the proposed CRBPNAs and show tuning and optimizing through choice of geometric and material parameters.

Plasmonic spectrum on 1D and 2D periodic arrays of rod-shape metal nanoparticle pairs with different core patterns for biosensor and solar cell applications

Simulations of surface plasmon resonance (SPR) on the near field intensity and absorption spectra of one-dimensional (1D) and two-dimensional (2D) periodic arrays of rod-shape metal nanoparticle (MNP) pairs using the finite element method (FEM) and taking into account the different core patterns for biosensor and solar cell applications are investigated. A tunable optical spectrum corresponding to the transverse SPR modes is observed. The peak resonance wavelength (λres) can be shifted to red as the core patterns in rod-shape MNPs have been changed. We find that the 2D periodic array of core–shell MNP pairs (case 2) exhibit a red shifted SPR that can be tuned the gap enhancement and absorption efficiency simultaneously over an extended wavelength range. The tunable optical performances give us a qualitative idea of the geometrical properties of the periodic array of rod-shape MNP pairs on SPRs that can be as a promising candidate for plasmonic biosensor and solar cell applications.

Size and Concentration Analysis of Gold Nanoparticles With Ultraviolet-Visible Spectroscopy

Spherical gold nanoparticles (GNPs) are synthesized by Turkevich Method and PEL 35 UV-VIS spectrophotometer recorded the wavelength and absorption of the Surface Plasmon Resonance (SPR) peak. The diameter and concentration of solute GNPs are calculated. The concentration of GNPs is done with Beer’s law. The average diameter of GNPs is done via the ratio of SPR peak to the absorbance at 450 nm. The diameters are compared to SEM scan of synthesized GNPs and Sigma-Aldrich values.

Low-Threshold and High Intensity Random Lasing Enhanced by MnCl₂.

Energy transfer is known to have a significant influence on random lasers. However, the study about the effect of energy transfer between metallic salt and dye molecules on random lasers is still lacking at present. Here, we investigate random lasing actions in Pyrromethene-597 (PM597), PM597-doped MnCl2 (manganese (II) chloride), PM597-doped polymer-dispersed liquid crystal (PDLC) and PM597-doped PDLC with MnCl2 capillary systems. We find that random lasing of the systems with MnCl2 exhibits lower threshold, higher intensity, sharper peak and variable resonance wavelength in comparison with the systems without MnCl2. This behavior is closely related to the decrease of fluorescence quenching effect and the enhancement of local field induced by energy transfer between MnCl2 and PM597. Red-shift of wavelength is observed with increasing dosage concentration of MnCl2 in the PM597-doped PDLC with MnCl2 system. Through the analysis of single-shot emission spectra of PM597-doped PDLC without and with MnCl2 systems, the role of MnCl2 in the coupling of lasing modes is confirmed. Lengths of laser oscillation cavities of the PM597-doped PDLC without and with MnCl2 systems are calculated by a power Fourier transform (PFT) analysis of their emission spectra. It well accounts for the effect of MnCl2 on the variation of the oscillation cavity.

Photonic crystal waveguide-based biosensor for detection of diseases

A biosensor is a device that is used to detect the analytes or molecules of a sample by means of a binding mechanism. A two-dimensional photonic crystal waveguide-based biosensor is designed with a diamond-shaped ring resonator and two waveguides: a bus waveguide and a drop waveguide. The sensing mechanism is based on change in refractive index of the analytes, leading to a shift in the peak resonant wavelength. This mechanism can be used in the field of biomedical treatment where different body fluids such as blood, tears, saliva, or urine can be used as the analyte in which different components of the fluid can be detected. It can also be used to differentiate between the cell lines of a normal and an unhealthy human being. Average value of quality factor for this device comes out to be 1082.2063. For different analytes used, the device exhibits enhanced sensitivity and, hence, it is useful for the detection of diseases.

High sensitivity plasmonic biosensor based on nanoimprinted quasi 3D nanosquares for cell detection

Quasi three-dimensional (3D) plasmonic nanostructures consisting of Au nanosquares on top of SU-8 nanopillars and Au nanoholes on the bottom were developed and fabricated using nanoimprint lithography with simultaneous thermal and UV exposure. These 3D plasmonic nanostructures were used to detect cell concentration of lung cancer A549 cells, retinal pigment epithelial (RPE) cells, and breast cancer MCF-7 cells. Nanoimprint technology has the advantage of producing high uniformity plasmonic nanostructures for such biosensors. Multiple resonance modes were observed in these quasi 3D plasmonic nanostructures. The hybrid coupling of localized surface plasmon resonances and Fabry–Perot cavity modes in the quasi 3D nanostructures resulted in high sensitivity of 496 nm/refractive index unit. The plasmonic resonance peak wavelength and sensitivity could be tuned by varying the Au thickness. Resonance peak shifts for different cells at the same concentration were distinct due to their different cell area and confluency. The cell concentration detection limit covered a large range of 5 × 102 to 1 × 107 cells ml−1 with these new plasmonic nanostructures. They also provide a large resonance peak shift of 51 nm for as little as 0.08 cells mm−2 of RPE cells for high sensitivity cell detection.

Relation between Silver Nanoparticle Formation Rate and Antioxidant Capacity of Aqueous Plant Leaf Extracts

Correlation between the antioxidant capacity and silver nanoparticle formation rates of pomegranate (Punica granatum), quince (Cydonia oblonga), chestnut (Castanea sativa), fig (Ficus carica), walnut (Juglans cinerea), black mulberry (Morus nigra), and white mulberry (Morus alba) leaf extracts is investigated at a fixed illumination. Silver nanoparticles formed in all plant leaf extracts possess round shapes with average particle size of 15 to 25 nm, whereas corresponding surface plasmon resonance peak wavelengths vary between 422 nm and 451 nm. Cupric reducing antioxidant capacity technique is used as a reference method to determine total antioxidant capacity of the plant leaf extracts. Integrated absorbance over the plasmon resonance peaks exhibits better linear relation with antioxidant capacities of various plant leaf extracts compared to peak absorbance values, with correlation coefficient values of 0.9333 and 0.7221, respectively.

Magnetic Response Property of Magnetic Fluid Photonic Crystal Microcavity

A kind of microcavity using magnetic fluid photonic crystal was presented,and its forming process was explained theoretically. Then the sensing property was studied,and the transmission characteristic was computed. The magnetic response properties of the proposed structure with the thickness of 6 μm and 0. 94 μm were analyzed respectively. It was found that the central wavelength of resonance peak would be blue-shifted about 4. 130 μm and 0. 076 μm.The maximum sensitivity was 243 nm / m T and 3. 8 nm / m T respectively. The sensor system exhibited the advantages of easy tuning,simple formation and high sensitivity,which would provide a newidea for optical sensor.

Optical properties and microstructure of Au nanorods via seed solution amount variation synthesized by seed-mediated growth method

The effect of seed solution amount variation on the aspect ratio and microstructure of gold nanorods (GNRs) using a seed-mediated method has been studied. The ultraviolet–visible (UV–Vis) absorption spectra for all samples shows that the wavelength of transverse surface plasmon resonance (TSPR) peak appeared at around 534 ± 10 nm regardless of the amount of seed solution used. The wavelength of longitudinal surface plasmon resonance (LSPR) of GNRs increased from 750 to 812 nm with seed solution amount being raised from 40 to 320 μl. Then, the wavelength of GNRs slightly decreased from 812 to 789 nm when the seed solution amount increased from 320 to 800 μl. The aspect ratio (AR) value measured from TEM images increased from 3.32 ± 0.07 to 4.03 ± 0.08 when the seed solution amount increased from 40 to 320 μl. Then, the AR value slightly decreased from 4.03 ± 0.08 to 3.95 ± 0.08 when the seed solution amount increased from 320 to 800 μl. The synthesized product of gold nanoparticles included spheres, nanorods and rhombus-shaped particles. The results of NBED and EDS revealed that the rhombus-shaped nanoparticles were bimetallic, containing gold and silver.

Wavelength-selective absorptance in GaAs, InP and InAs nanowire arrays

The absorptance in vertical nanowire (nw) arrays is a result of three optical phenomena: radial mode resonances, near-field evanescent wave coupling, and Fabry–Perot (F–P) modes. The contribution of these optical phenomena to GaAs, InP and InAs nw absorptance was simulated using the finite element method. The study compared the absorptance between finite and semi-infinite nw lengths with varying geometrical parameters, including the nw diameter, length and array period. Simulation results showed that the resonance peak wavelength of the HE11 and HE12 radial modes linearly red-shifted with increasing nw diameter. The absorptance and spectral width of the resonance peaks increased as the nw length increased, with an absorptance plateau for very long nws that depended on diameter and period. Near-field coupling between neighboring nws was observed to increase with decreasing period. The effect of F–P modes was more pronounced for shorter nws, with a significant enhancement of HE12 over HE11 absorptance. Engineering of nw arrays to take advantage of these optical phenomena for multi-spectral photodetector applications is discussed.

The Discovery of Plasmon Resonance in Germanide Nanowires Grown on Cu Foil

Free-standing and single-crystalline Cu3Ge nanowires (NWs) were synthesized by a vapor-phase deposition method on the Cu foil. The NWs are grown along the [010] direction via a vapor–solid mechanism. The localized surface plasmon resonance of individual NWs on a Si substrate is investigated using the dark-field scattering spectroscopy. The resonance peak wavelength for NWs with different diameters is observed, which ranges from 500 to 550 nm. This study proves the existence and provides an insight for understanding the LSPR property of free-standing Cu3Ge NWs.

Aspect ratio control of Au nanorods via covariation of the total amount of HAuCl4 and ascorbic acid

Controlling the aspect ratio (AR) of gold nanorods (GNRs) via covariation of the total concentrations of HAuCl4 ([HAuCl4]) and ascorbic acid ([AA]) has been studied. Characteristics of GNRs were examined by transmission electron microscopy (TEM) and ultraviolet–visible (UV–vis) absorption spectrophotometry. TEM results showed that single crystalline GNRs grew along an elongated growth direction of [100]. TEM results also revealed that the quantity of plate shaped and nearly spherical nanoparticles increased as the total amount of [HAuCl4] and [AA] decreased. The AR value measured from TEM images decreased from 4.74 to 2.41 as the total amount of [HAuCl4] and [AA] was increased from 0.305 to 2.44mM. The UV–vis absorption spectra of all samples showed that the wavelength of transverse surface plasmon resonance (TSPR) peak appeared at around 530nm for all samples. The wavelength of longitudinal surface plasmon resonance (LSPR) peak increased from 640 to 894nm as the total amount of [HAuCl4] and [AA] decreased from 2.44 to 0.305mM. The wavelength of LSPR peak shows a red-shifted effect except when the total amount of [HAuCl4] and [AA] was 0.122mM.

Optical Properties of Pure and Alloyed Silver-Copper Nanoparticles Embedded and Coupled in Dielectric Matrixes

In this study by using the boundary element method, influence of various parameters on the response to electromagnetic radiation for pure and alloyed silver-copper was investigated. The results demonstrate decreasing interparticle gap from 20nm to 1nm for silver coupled nanoparticles leads to shifting the wavelength of optical extinction peak from 362nm to 393nm. Decreasing interparticle gap from 20nm to 1nm for Cu coupled nanoparticles leads to shifting the wavelength of optical extinction peak from 323nm to 336nm. By an increase in the medium refractive index of 1 to 2 the peak of optical extinction for a coupled Cu nanoparticles with 1nm gap distance the wavelength of plasmon resonance peak shifted from 336nm to 366nm and longitudinal plasmon resonance peak shifted from 498nm to 559nm. By changing the composition of an alloy of copper and silver nanoparticles with diameter of 10nm in dielectric matrix with refractive index 1.3 the wavelength of plasmon resonance peak shifted from 378nm for pure silver nanoparticles to 530nm for pure copper nanoparticles. In addition for Cu-Ag alloy coupled nanoparticles with 1nm interparticle gap, the wavelength of resonance peak shifted from 420nm for pure silver nanoparticles to 544nm for pure copper nanoparticles. In the case of embedded nanoparticles for coupled silver nanoparticles with 6nm gap distance, the wavelength of resonance peak shifted from 396nm to 409nm, and for coupled silver nanoparticles with 2nm gap distance, the wavelength of resonance peak shifted from 414nm to 430nm. Furthermore for coupled Cu nanoparticles with 2nm gap distance, the wavelength of resonance peak shifted from 575nm to 582nm. The results could be employed for plasmatic sensor design and fabrication.