Fig. 1
a Energy transfer process in…
Fig. 1
a Energy transfer process in Stokes (left) and anti-Stokes (right) Raman scattering, in…
Fig. 1a Energy transfer process in Stokes (left) and anti-Stokes (right) Raman scattering, in both scattering processes, the lifetime of the excited state is probabilistic and spontaneous. In Stokes Raman scattering, the initial (ro-)vibrational energy |i〉 of the scattering material is less than that of the final state |f〉, the scattered light has less energy than the pump light. In anti-Stokes scattering, the initial (ro-)vibrational energy |i〉 of the scattering medium is greater than that of the final state |f〉, the scattered light has more energy than the pump light. b Coherent anti-Stokes Raman scattering (CARS). CARS is a four-wave mixing process of pump, Stokes, probe and anti-Stokes light in which the emission of anti-Stokes light is coherently induced through an intermediate (ro-)vibrational energy state population inversion. c Surface-enhanced Raman scattering (SERS). The incident pump light induces a surface plasmon resonance. The resultant enhancement of the oscillatory electro-magnetic (EM) field strength (shown in blue) on the surface intensifies the light-matter interaction and consequently increases the intensity of the Raman scattered light. d Tip-enhanced Raman scattering (TERS). The incident pump light induces a tip-surface plasmon resonance associated with the plasmonically active tip. The resultant enhancement of the oscillatory EM field strength (shown in blue) is localised to the vicinity of the tip apex. The lighting rod effect (illustrated by curved black arrows) intensifies the light-matter interaction in the tip region and provides high-resolution (beyond the diffraction limit of light) Raman imaging. a, b adapted from [1]. c adapted from [111]. d adapted from [112]
Fig. 2
a Energy level diagram of…
Fig. 2
a Energy level diagram of stimulated Raman scattering (SRS). SRS is the induced…
Fig. 2a Energy level diagram of stimulated Raman scattering (SRS). SRS is the induced emission of Stokes light by the coherent interaction of the pump and Stokes light with the material. Unlike spontaneous Raman scattering where the lifetime of the state |r〉 and the energy of the final state |f〉 are probabilistic, in SRS, the (ro-)vibration of the molecule or lattice is coherently driven by the difference frequency of the pump and Stokes light. b Comparison of spontaneous Raman scattering and SRS of bulk and droplet ethanol. The spontaneous measurements were performed in a cuvette (bulk ethanol). The SRS measurements were performed in a droplet of ethanol which acted as an optical resonator for the Stokes light. b reproduced with permission from the OSA [114]
Fig. 3
a Typical confocal Raman spectroscopy…
Fig. 3
a Typical confocal Raman spectroscopy setup. The pump laser is spatially filtered through…
Fig. 3a Typical confocal Raman spectroscopy setup. The pump laser is spatially filtered through a pinhole. The back-scattered Raman light is spatially filtered and spectrally filtered through a notch filter. The Raman light is analysed by a spectrometer and a charge-coupled device (CCD). Hyperspectral images are obtained by raster scanning the sample. b Typical CARS setup. Two laser sources provide the pump and Stokes light and are synchronised through a picosecond path difference mirror setup. In this setup, the incident light is focused through an optically transmissive sample substrate. Both the forward scattered light (F-CARS) and epi-scattered light (E-CARS) are spectrally filtered by band-pass filters and are subsequently detected by two avalanche photodiodes. CARS images are obtained by raster scanning the sample. c Typical SERS setup. The pump laser is coupled into a dark-field microscope in which the Raman light is edge-filtered and detected through a monochromator and EMCCD. The white-light source and dark-field mask provides the means for dark-field spectroscopy. The dark-field spectra of each plasmonically active nanoparticle are recorded through a secondary spectrometer (top right in c). An imaging CCD camera is used to automatically find and centre each nanoparticle. d Typical TERS setup. The pump laser light is spatially filtered and passed through a half-wave plate. The evanescent mask ensures that only high numerical aperture (NA) pump light is incident on the sample such that total internal reflection occurs at the substrate-sample interface. This ensures that the tip apex is only illuminated by the evanescent light to achieve nanoconcentrated light in the vicinity of the tip. The reflected Raman light is filtered by an apertured mask (to remove any residual large NA pump light) and a notch filter. The Raman light is analysed by a spectrometer and a CCD. Hyperspectral images are obtained by raster scanning the sample. F, filter; M, mirror; RL, Raman light; CCD, charge-coupled device; PH, pinhole; BE, beam expander; D-BS, dichroic beam splitter; OBJ, Large numerical aperture (NA) lens; EMCCD, electron-multiplying charge-coupled device. a adapted from [162]. b adapted from [116]. c adapted from [85]. d adapted from [86]
Fig. 4
a i Smooth metallic (silver;…
Fig. 4
a i Smooth metallic (silver; Ag) film-coated dielectric (silicon-dioxide; SiO 2 ) atomic…
Fig. 4a i Smooth metallic (silver; Ag) film-coated dielectric (silicon-dioxide; SiO2) atomic force microscope (AFM) tip. a ii SEM image of a Ag-coated AFM tip. After Ag coating by thermal evaporation, a thin granular Ag layer is deposited onto the tip. b i, Rough Ag-nanoparticle-coated SiO2 AFM tip. b ii SEM image of rough Ag-grain-coated SiO2 AFM tip formed during the thermal evaporation process. c i Single Ag nanoparticle attached to the apex of a SiO2 AFM tip. c ii SEM image of an AFM tip after photoreduction to selectively fabricate an Ag nanoparticle at the tip apex. d i Ag-coated SiO2 AFM tip with a focused ion beam (FIB) milled gap. d ii SEM image of antenna fabricated by FIB milling of annular ring and subsequent Ag thermal evaporation from under the tip. The mushroom shape shadows the annular ring from Ag coating. e i Illustration of side illumination TERS for surface plasmon polariton (SPP) nanofocusing. OBJ, objective. e ii Schematic of the tip structure for SPP nanofocusing which is composed of a SiO2 pyramidal structure (AFM tip) and a Ag film on the surface. The incident light is coupled to the surface by the FIB-fabricated grating nanostructure. e iii SEM image of a Ag-coated SiO2 tip with a FIB-fabricated grating structure. a i, b i and ii, c i reproduced from Ref. [198] with permission from The Royal Society of Chemistry. (ref.). a ii reprinted with permission from [86]. c ii Reprinted from [199] with permission from IOP. d i Adapted from [200]. d ii Reprinted from [200] with permission from IOP. e i Adapted from [201]. e ii and iii reproduced from Ref. [201] with permission from The Royal Society of Chemistry
Fig. 5
a Spontaneous Stokes and anti-Stokes…
Fig. 5
a Spontaneous Stokes and anti-Stokes Raman spectrum of carbon tetrachloride (liquid) excited by…
Fig. 5a Spontaneous Stokes and anti-Stokes Raman spectrum of carbon tetrachloride (liquid) excited by an argon ion laser, ν ~ p =20487 cm−1. The spectrum is presented according to recommendations of the International Union of Pure and Applied Chemistry. b i Raman spectra of thin multi-layer (nL) and bulk MoS2 films. The solid line for the 2 L spectrum is a double Voigt fit through data (circles for 2L, solid lines for the remainder). b ii Frequencies of E 2 g 1 and A1g Raman modes (left vertical axis) and their difference (right vertical axis) as a function of the number of layers. b iii, iv spatial maps (23 μm × 10 μm) of Raman frequency of E 2 g 1 (iii) and A1g (iv) from a sample of thin MoS2 films deposited on a SiO2/Si substrate. b v Atomic displacements of the four Raman-active modes and one infrared-active mode (E1u) in the unit cell of the bulk MoS2 crystal as viewed along the [1000] direction. c Microscopic image of nebulised ammonium sulphate aerosol particles on: i, Klarite; iii, silicon wafer. ii, iv Raman mapping image of sample (i) and (iii), respectively. d i Pseudo colour broadband CARS image of tumour and normal brain tissue, with nuclei highlighted in blue, lipid content in red and red blood cells in green. d ii Broadband CARS image and axial scan (below) with nuclei highlighted in blue and lipid content in red. d iii Broadband CARS image with nuclei highlighted in blue, lipid content in red and CH3 stretch–CH2 stretch in green. NB, normal brain; T, tumour cells; RBC, red blood cells; L, lipid bodies; WM, white matter. d iv Single-pixel spectra. e Raman thermography measurements across the active region of a high electron mobility transistor on SiC substrate with both E2 and A1 (LO) phonons considered to compensate for thermal stress. Device temperature rise determined using either E2 or A1 (LO) phonon mode alone (neglecting thermal stress) is shown in the top left insert. f (left) illustration of the manipulation of a straight isolated carbon nanotube (CNT) lying on a glass substrate by the sharp apex of an AFM tip. f (right) two-dimensional image of a CNT constructed by colour-coding the frequency position of the G+ vibrational mode in TERS spectra. The colour variation shows the strain distribution along the CNT at high-spatial resolution. a reproduced with permissions from [1]. b Adapted with permission from [217]. c Reprinted with permission from [96]. d Reprinted by permission from [167]. e Reprinted from [218]. f Reprinted by permission from [219].
Fig. 6
a Comparison of conventional and…
Fig. 6
a Comparison of conventional and fast-polarisation SRS on multi-lamellar lipid vesicles (MLVs). a…
Fig. 6a Comparison of conventional and fast-polarisation SRS on multi-lamellar lipid vesicles (MLVs). a i–iii the composite images show absolute local molecular order (S2) and mean molecular orientation (φ2) values represented as coloured sticks. a i (top) Conventional polarisation SRS on a MLV using step angles of 5° (acquisition time 112 s); the total measured intensity (a0) is represented as a grey-scaled background. a i (bottom), fast-polarisation SRS on the same MLV (acquisition time 1 s); the acousto-optic modulation (AOM) is shown as a grey-scaled background. a ii Fast-polarisation dynamics SRS images of lipid order in a MLV taken at different times of the observation sequence shown; the AOM is shown as a grey-scaled background. Zoomed regions at the upper part of the MLV contour show no change in lipid order during the measurement over tens of seconds. a iii Fast-polarisation dynamics of lipid order in a thin lipid membrane. Coloured sticks show S2 and φ2 and the grey-scale background shows the AOM amplitude. b i SRS flow cytometry (SRS-FC) setup. b ii Colour-coded constrained principle component analysis (CPCA) scatter plot of SRS-FC spectra from mixed PMMA (red), PS (blue) and PCL (green) beads. The principle components (PC 1 and PC 2) are distinguished subpopulations of mixed polymer beads according to the distinct Raman spectra. Data were acquired in 6 s using a bead mixture with a concentration of 2% solids. The beads were 10 μm in diameter. b iii (left) Colour-coded CPCA scatter plot from SRS-FC analysis of lipid amount in 3T3-L1 cells with principle components differentiated through quantification of distinct chemical compositions inside single cells. Data were acquired in 3 s. b iii (right) SRS images of the two 3T3-L1 cell types. c i Illustration of the generation and amplification of a new orbital angular momentum (OAM) laser in a configuration with no initial OAM using a Hermite-Gaussian (TEM) laser. c ii, iii Simulation of the generation and amplification of a new OAM mode from initial configurations with no net OAM. c ii The initial seed TEM modes in x- and y-directions (top and bottom, respectively). c iii The new OAM mode electric field components at z = 3.5 mm in x- and y-directions (top and bottom, respectively). The new mode is linearly polarised in the x- and y-directions with l1x = l1y = − 1 from an initial seed polarised in the x-direction with a TEM01 mode and in the y-direction with a TEM10 mode that is π/2 out of phase with respect to the TEM01 mode polarised in x. The pump is a Gaussian laser polarised at 45°. Projections in the (x,y) plane (blue-white-red) show the normalised vector potential (ϕ0) field envelope of the new OAM mode at the longitudinal slice where the laser intensity is maximum. The envelope of the 3D laser intensity is also shown in blue-green-red colours and normalised vector potential isosurfaces in blue and red. The values of the laser vector potential illustrated by the isosurfaces are shown in c (ii) and c (iii). a reproduced with permission from the OSA [259]. b reproduced with permission from the OSA [260]. c Adapted from [46] and licenced under CC BY 4.0.
Fig. 7
a Simultaneous two-colour CARS imaging…
Fig. 7
a Simultaneous two-colour CARS imaging with real-time nonresonant background subtraction from a mouse…
Fig. 7a Simultaneous two-colour CARS imaging with real-time nonresonant background subtraction from a mouse tissue sample at a surface depth of 45 μm. a i CARS image acquired at 2940 cm−1 (CH3 stretching vibration). a ii Off-resonance background CARS image at 2770 cm−1. a iii Background-free image of (i) at 2940 cm-1 after subtraction of the nonresonant background (ii). b Multi-lamellar lipid vesicle (MLV) imaged with conventional (i) and symmetry-resolved CARS (SR-CARS) at 1133 cm-1 (ii) and (iii). ii The incident circularly polarised pump, Stokes, probe and anti-Stokes light have co-rotating handedness (mF = 0). iii the incident circularly polarised pump, probe and anti-Stokes light have co-rotating handedness and the Stokes light has counter rotating handedness (mF = 2). c High-speed polarisation-resolved CARS image sequence on a MLV moving over the sample surface taken at different times of the observation sequence shown as a composite image of S2 and φ2 as coloured sticks and with the acousto-optic modulation (AOM) as a grey background. a reproduced with permission from the OSA [278]. b Adapted from [289] and licenced under CC BY 4.0. c reproduced with permission from the OSA [259].
Fig. 8
a i Illustration of tip-enhanced…
Fig. 8
a i Illustration of tip-enhanced dual-wavelength nanofocused CARS on a multi-walled carbon nanotube…
Fig. 8a i Illustration of tip-enhanced dual-wavelength nanofocused CARS on a multi-walled carbon nanotube (MWCNT). a ii Energy diagram for ω-CARS and 2ω-CARS. When the difference frequency between pump and Stokes light matches the vibrational mode of the molecule, it is resonantly excited. When ω and 2ω-probe light is simultaneously incident within the dephasing time, ω- and 2ω-CARS photons are respectively generated. b i Simultaneous topographical 2ω-CARS imaging of a MWCNT. b ii Composite image of three 2ω-CARS images of the MWCNT using the 2ω-CARS spectrum from D- (red), G- (blue) and 2D- (green) bands. Reprinted with permission from [155]
RetroSearch is an open source project built by @garambo | Open a GitHub Issue
Search and Browse the WWW like it's 1997 | Search results from DuckDuckGo
HTML:
3.2
| Encoding:
UTF-8
| Version:
0.7.3