Laser spectroscopy imaging technique coupled withnanomaterials for cancer diagnosis: A review

Laser spectroscopic imaging techniques have received tremendous attention in the-eld of cancer diagnosis due to their high sensitivity,high temporal resolution,and short acquisition time.However,the limited tissue penetration of the laser is still a challenge for the in vivo diagnosis of deep-seated lesions.Nanomaterials have been universally integrated with spectroscopic imaging techniques for deeper cancer diagnosis in vivo.The components,morphology,and sizes of nanomaterials are delicately designed,which could realize cancer diagnosis in vivo or in situ.Considering the enhanced signal emitting from the nanomaterials,we emphasized their combination with spectroscopic imaging techniques for cancer diagnosis,like the surface-enhanced Raman scattering(SERS),photoacoustic,fluorescence,and laser-induced breakdown spectroscopy(LIBS).Applications ofthe above spectroscopic techniques offer new prospectsfor cancer diagnosis.

Control and data acquisition system for collinear laser spectroscopy experiments

A control and data acquisition system was implemented for the recently developed collinear laser spectroscopy setup.This system is dedicated to data recording,storage,processing,monitoring of the beam intensity and energy,and visualization of various spectra.In comparison to the conventional resonance nuclear reaction system,the key technique is the precise synchronization of the detected counts with the actual scanning voltage(or probing laser frequency).The functions of the system were tested by measuring the hyperfine structure spectra of stable calcium(e.g.,^(40)Ca^(+))and radioactive potassium(e.g.,^(38)K)in the bunched and continuous modes,respectively.This system will be routinely applied and further improved in subsequent laser spectroscopy experiments on unstable isotopes at the Beijing Radioactive Ion-beam Facility(BRIF).

Commissioning of a high-resolution collinear laser spectroscopy apparatus with a laser ablation ion source

Collinear laser spectroscopy is a powerful tool for studying the nuclear spins,electromagnetic moments,and charge radii of exotic nuclei.To study the nuclear properties of unstable nuclei at the Beijing Radioactive Ion-beam Facility(BRIF)and the future High Intensity Heavy-ion Accelerator Facility(HIAF),we developed a collinear laser spectroscopy apparatus integrated with an offline laser ablation ion source and a laser system.The overall performance of this state-of-the-art technique was evaluated,and the system was commissioned using a bunched stable ion beam.The high-resolution optical spectra for the 4s ^(2)S_(1/2)→4p^(2)P_(3/2)(D2)ionic transition of ^(40;42;44;48)Ca isotopes were successfully measured.The extracted isotope shifts relative to ^(40)Ca showed excellent agreement with the literature values.This system is now ready for use at radioactive ion beam facilities such as the BRIF and paves the way for the further development of higher-sensitivity collinear resonance ionization spectroscopy techniques.

Cs 5D_(5/2)-6F 728 nm Laser Spectroscopy with Single Pumping Laser

The sub-Doppler absorption laser spectroscopy at 728 nm transition from the 5D5/2 state to the 6 F state of cesium with linewidth near 10 MHz is first experimentally performed with indirect pumping from the ground state 6S_(1/2)to the state 7P_(3/2)by a 455.5 nm diode laser.Using a 455.5 nm diode laser as an indirect pump laser,several excited states will be populated due to spontaneous decay from the 7P state.We first implement the sub-Doppler absorption laser spectroscopy at 728 nm from the 5D_(5/2)state to the 6F state when Cs atoms within thermal glass cell decay to the 5D_(5/2) state.Due to velocity transfer effect,the hyperfine structure of 5D_(5/2)shows a mixed and complicated pattern but very clear structure when the 455.5 nm pumping laser is counter-propagating(or co-propagating)with the 728 nm probing laser.

Determination of Gum Arabic (<i>Acacia nilotica</i>) Constituents Using Laser Induced Breakdown Spectroscopy

In this work, Laser Induced Breakdown Spectroscopy (LIBS) was used to determine the constituent of Gum Arabic (Acacia nilotica) collected from five different locations in Sudan. Gum samples were irradiated with 80 mJ pulse energy of Nd-YAG laser (1064 nm) and Atomic spectra Database was used for the spectral analysis of the plasma emitted from these samples. It was found that the samples contain the elements C, O, H, S, N, P, Na, Mg, Ca, Fe, Cr, Mn, Co with different amounts. Some elements like (Ti, Br, Ar, Th, Kr, Sc and Pr) are recorded here for the first time.

Influence of the position relationship between gas–liquid interface and laser focus on plasma evolution characteristics in jet LIBS technology

In order to understand the characteristics of breakdown process,plasma evolution and spectral emission in liquid jets laser-induced breakdown spectroscopy methods under the influence of the position variation between laser focus and gas–liquid interface,this work takes the plasma generated by laser-induced liquid jets as the object of study and discusses the changes in the spatial and temporal evolution characteristics and spectral radiation of the plasma when the position parameters between the laser focal point and the gas–liquid interface are different.The initial breakdown position is always between the front interface and the focus when the laser focus moves along the vertical direction of the interface,forming a phenomenon like’interface effect’.The relationship between laser pulse energy and breakdown probability exhibits a law similar to a‘hysteresis curve’in the study of breakdown threshold.In this work,plasma with smaller size,rounder shape,stronger radiation,higher temperature,and higher density can be produced when the focus position is in the liquid column 0.2 mm away from the front interface.Simultaneously,the spectral signal intensity and signal-to-back ratio of the characteristic peaks of target elements in water reach maximum values,and the spectral signal becomes more stable(relative standard deviation value reaches 2%).The Ca element’s ion radiation at 393.366 nm and atomic radiation at 422.673 nm are studied using narrow-band filtering imaging and time-space resolution spectroscopy.The findings demonstrate that the laws of ion and atomic radiation are not perfectly consistent in space and time.

Single-mode GaSb-based laterally coupled distributed-feedback laser for CO_(2)gas detection

We report on a GaSb-based laterally coupled distributed feedback(LC-DFB)laser with Cr gratings operating at 2004 nm for CO_(2)detection application.Butterfly packaged with single-mode fiber pigtailed,the laser diode operates in the continuous-wave mode in a temperature range from-10℃to 60℃,with a maximum output power of 2 mW and a maximum side-mode suppression ratio over 30 dB.Wavelength-modulated absorption spectroscopy of CO_(2)demonstrates the applicability of the LC-DFB laser to tunable diode laser absorption spectroscopy.Furthermore,the diode junction temperature,which is measured by using the wavelength shift method,exhibits a maximum value of 17℃in the single-mode operation range.

High-Resolution Stark Spectroscopy of Ba Highly-Excited States by Diode Laser Technique

High-resolution atomic-beam laser spectroscopy has been performed to study Stark effect of Ba atom. Stark spectra have been observed at various electric fields for Ba highly excited states. The scalar polarizability of the transition from 6s5d3D2 to 5d6p3F3 at 728.0 nm and the tensor polarizability of the 3F3 level have been determined for the first time, to be αs = -89.8 (12) kHz/(kV/cm)2 and αt = -133.7 (20) kHz/(kV/cm)2, respectively.

Measurements of argon metastable density using the tunable diode laser absorption spectroscopy in Ar and Ar/O2

Densities of Ar metastable states 1s_5 and 1s_3 are measured by using the tunable diode laser absorption spectroscopy(TDLAS) in Ar and Ar/O2 mixture dual-frequency capacitively coupled plasma(DF-CCP). We investigate the effects of high-frequency(HF, 60 MHz) power, low-frequency(LF, 2 MHz) power, and working pressure on the density of Ar metastable states for three different gas components(0%, 5%, and 10% oxygen mixed in argon). The dependence of Ar metastable state density on the oxygen content is also studied at different working pressures. It is found that densities of Ar metastable states in discharges with different gas components exhibit different behaviors as HF power increases. With the increase of HF power, the metastable density increases rapidly at the initial stage, and then tends to be saturated at a higher HF power. With a small fraction(5% or 10%) of oxygen added in argon plasma, a similar change of the Ar metastable density with HF power can be observed, but the metastable density is saturated at a higher HF power than in the pure argon discharge. In the DF-CCP, the metastable density is found to be higher than in a single frequency discharge, and has weak dependence on LF power. As working pressure increases, the metastable state density first increases and then decreases,and the pressure value, at which the density maximum occurs, decreases with oxygen content increasing. Besides, adding a small fraction of oxygen into argon plasma will significantly dwindle the metastable state density as a result of quenching loss by oxygen molecules.

Evaluation of gases'molecular abundance ratio by fiber-optic laser-induced breakdown spectroscopy with a metal-assisted method

A metal-assisted method is proposed for the evaluation of gases’molecular abundance ratio in fiber-optic laser-induced breakdown spectroscopy(FO-LIBS).This method can reduce the laser ablation energy and make gas composition identification possible.The principle comes from the collision between the detected gases and the plasma produced by the laser ablation of the metal substrate.The interparticle collision in the plasma plume leads to gas molecules dissociating and sparking,which can be used to determine the gas composition.The quantitative relationship between spectral line intensity and molecular abundance ratio was developed over a large molecular abundance ratio range.The influence of laser ablation energy and substrate material on gas quantitative calibration measurement is also analyzed.The proposed metal-assisted method makes the measurement of gases’molecular abundance ratios possible with an FO-LIBS system.

Aqueous ruthenium detection by microwave-assisted laser-induced breakdown spectroscopy

Aqueous ruthenium was detected in real-time under ambient conditions using microwaveassisted laser-induced breakdown spectroscopy(MW-LIBS).A 10 mJ laser energy and 750 W microwave power were directed at an open liquid jet sample of ruthenium.It was observed that,for liquid flow,the coupling efficiency between the microwave and the laser-induced plasma was limited to 43%.The improvement in the ruthenium’s signal-to-noise ratio with MW-LIBS,with respect to LIBS,was 76-fold.Based on MW-LIBS,the limit of detection for aqueous ruthenium was determined to be 957±84 ppb.

Detection of Nitric Oxide with Faraday Rotation Spectroscopy at 5.33μm

We report the development of a static magnetic eld Faraday rotation spectrometer for NO detection.A 5.33μm continuous-wave quantum cascade laser was used as the probing laser.Line absorption at 1875.81 cm^−1(2Π3=2Q(3/2),v=1←0)was chosen for the detection.By using a Chernin type multipass cell,a detection precision of 1.15 ppbv(1σ,1s)was achieved with an absorption pathlength of 108 m.This value was reduced to 0.43 ppbv by increasing the data-acquisition time to 15 s.

Laser induced fluorescence diagnostic for velocity distribution functions:applications,physics,methods and developments

With more than 30 years of development,laser-induced fluorescence(LIF)is becoming an increasingly common diagnostic to measure ion and neutral velocity distribution functions in different fields of studies in plasma science including Hall thrusters,linear devices,plasma processing,and basic plasma physical processes.In this paper,technical methods used in the LIF diagnostic,including modulation,collection optics,and wavelength calibration techniques are reviewed in detail.A few basic physical processes along with applications and future development associated with the LIF diagnostics are also reviewed.

Three-dimensionalization via control of laser-structuring parameters for high energy and high power lithium-ion battery under various operating con ditions

Laser-structuring is an effective method to promote ion diffusion and improve the performance of lithium-ion battery(LIB)electrodes.In this work,the effects of laser structuring parameters(groove pitch and depth)on the fundamental characteristics of LIB electrode,such as interfacial area,internal resistances,material loss and electrochemical performance,are investigated,LiNi_(0.5)Co_(0.2)Mn_(0.3)O_(2) cathodes were structured by a femtosecond laser by varying groove depth and pitch,which resulted in a material loss of 5%-14%and an increase of 140%-260%in the in terfacial area between electrode surface and electrolyte.It is shown that the importance of groove depth and pitch on the electrochemical performance(specific capacity and areal discharge capacity)of laser-structured electrode varies with current rates.Groove pitch is more im porta nt at low current rate but groove depth is at high curre nt rate.From the mapping of lithium concentration within the electrodes of varying groove depth and pitch by laser-induced breakdown spectroscopy,it is verified that the groove functions as a diffusion path for lithium ions.The ionic,electronic,and charge transfer resistances measured with symmetric and half cells showed that these internal resistances are differently affected by laser structuring parameters and the changes in porosity,ionic diffusion and electronic pathways.It is demonstrated that the laser structuring parameters for maximum electrode performance and minimum capacity loss should be determined in consideration of the main operating conditions of LIBs.

Monitoring the Laser Ablation Process of Paint Layers by PILA Technique

The spectrum analysis obtained by Fast Fourier Transform of the Photoacoustic In-duced by Laser Ablation (PILA) during laser assisted paints removal process is de-scribed, in order to identify the presence of paint components on a metallic surface, optimize the ablation rate and propose the method as a cleaning process monitoring. The process was carried out using a low-cost experimental setup which includes a burst-mode Nd:YAG laser, an electret microphone, an audio amplifier device and an oscilloscope, to record the acoustic pulse and analyze it. The samples surface mor-phology was characterized by Optical Microscopy and Optical Coherence Tomography (OCT) before and after irradiation to visualize the formation of craters. As additional monitoring technique, the Laser Induced Breakdown Spectroscopy (LIBS) was used. The potential of the analysis for qualitative monitoring of coating removal was demonstrated due to the coincidence of the information provided by LIBS and PILA techniques.

Temporal and spatial dynamics of optical emission from laser ablation of the first wall materials of fusion device

Laser-induced breakdown spectroscopy(LIBS) has been developed to in situ diagnose the chemical compositions of the first wall in the EAST tokamak. However, the dynamics of optical emission of the key plasma-facing materials, such as tungsten, molybdenum and graphite have not been investigated in a laser produced plasma(LPP) under vacuum. In this work, the temporal and spatial dynamics of optical emission were investigated using the spectrometer with ICCD.Plasma was produced by an Nd:YAG laser(1064 nm) with pulse duration of 6 ns. The results showed that the typical lifetime of LPP is less than 1.4 μs, and the lifetime of ions is shorter than atoms at ~10^(-6)mbar. Temporal features of optical emission showed that the optimized delay times for collecting spectra are from 100 to 400 ns which depended on the corresponding species. For spatial distribution, the maximum LIBS spectral intensity in plasma plume is obtained in the region from 1.5 to 3.0 mm above the sample surface. Moreover, the plasma expansion velocity involving the different species in a multicomponent system was measured for obtaining the proper timing(gate delay time and gate width) of the maximum emission intensity and for understanding the plasma expansion mechanism. The order of expansion velocities for various species is V_C^+> V_H> V_(Si)^+> V_(Li)> V_(Mo)> V_W.These results could be attributed to the plasma sheath acceleration and mass effect. In addition, an optimum signal-to-background ratio was investigated by varying both delay time and detecting position.

Single-cell analysis reveals microbial spore responses to microwave radiation

To determine the effects of microwave radiation at the molecular level as well as on the germination,growth and morphology of dry spores at the single-cell level.Dry Bacillus aryabhattai MCCC 1K02966 spores were microwave-treated at different powers and characterized using single-cell optical technology.As determined by laser tweezers Raman spectroscopy,the Ca^(2+)-dipicolinic acid content increased and nucleic acid denaturation occurred in response to microwave treatment.Livecell microscopy revealed that the germination and growth rates decreased as the microwave power increased.With respect to morphology,atomic force microscopy(AFM)demonstrated that spores became wrinkled and rough after microwave treatment.Furthermore,spores became smaller as the microwave power increased.Microwave treatment can damage DNA,and high-power microwaves can inhibit the germination of spores and reduce spore volumes.These results provide a new perspective on the responses of living single cells to microwave radiation and demonstrate the application of various new techniques for analyses of microorganisms at the single-cell level.

Absorption Line Profile Recovery Based on TDLS and MEMS Micro-Mirror for Photoacoustic Gas Sensing

A novel and efficient absorption line recovery technique is presented.A micro-electromechanical systems(MEMS) mirror driven by an electrothermal actuator is used to generate laser intensity modulation through the mirror reflection.Tunable diode laser spectroscopy(TDLS) and photoacoustic spectroscopy(PAS) are used to recover the target absorption line profile which is compared with the theoretical Voigt profile.The target gas is 0.01% acetylene(C2H2) in a nitrogen host gas.The laser diode wavelength is swept across the P17 absorption line of acetylene at 1 535.4 nm by a current ramp,and an erbium-doped fibre amplifier(EDFA) is used to enhance the optical intensity and increase the signal-to-noise ratio(SNR).A SNR of about 35 is obtained with 100 mW laser power from the EDFA.Good agreement is achieved between the experimental results and the theoretical simulation for the P17 absorption line profile.

The Puzzle of the La I Lines 6520.644 A and 6519.869 A

The strong La line 6520.644 ? is present in a Fourier Transform Spectrum (signal to noise ratio of 240), but its wavelength in commonly used tables (e.g. [1]) is given as 6520.770 ?, while in [2] the wavelength is given as 6520.74 ?, unclassified, with the remark “h” (hazy). The line could not be classified using known energy levels of the La atom (La I) and its first ion (La II). It appears as a single broadened peak. By a combination of laser optogalvanic spectroscopy, laser-induced fluorescence and Doppler-reduced saturation spectroscopy we could introduce a new even parity La I energy level, 35449.041 cm -1, J = 13/2, with hyperfine (hf) constants A = ?8.0(5) MHz, B = 10(10) MHz. For a second, up to now unknown neighbouring La I line (wavelength 6519.869 ?) we introduced another even parity energy level involved in the formation of the line, 41207.994 cm?-1, J = 13/2, A = 91.6(5) MHz, B = 170(50) MHz. We tried also to explain why in old tables the wavelength given was so different.

In situ measurement on nonuniform velocity distributionin external detonation exhaust flow by analysis ofspectrum features using TDLAS

Instantaneous and precise velocity sensing is a critical part of research on detonation mechanism and flow evolution.This paper presents a novel multi-projection tunable diode laser absorption spectroscopy solution,to provide a real-time and reliable measurement of velocity distribution in detonation exhaust flow with obvious nonuniformity.Relations are established between overlapped spectrums along probing beams and Gauss velocity distribution phantom according to the frequency shifts and tiny variations in components of light-of-sight absorbance profiles at low frequencies analyzed by the fast Fourier transform.With simulated optical measurement using H2O feature at 7185.6 cm-1 carried out on a phantom generated using a simulation of two-phase detonation by a two-fluid model,this method demonstrates a satisfying performance on recovery of velocity distribution profiles in supersonic flow even with a noise equivalent absorbance up to 2×10^(-3).This method is applied to the analysis of rapidly decreasing velocity during a complete working cycle in the external flow field of an air-gasoline detonation tube operating at 25 Hz,and results show the velocity in the core flow field would be much larger than the arithmetic average from traditional tunable diode laser doppler velocimetry.This proposed velocity distribution sensor would reconstruct nonuniform velocity distribution of high-speed flow in low cost and simple operations,which broadens the possibility for applications in research on the formation and propagation of external flow filed of detonation tube.