Laser-induced Heating Effect Research Articles

Effect of Laser-Induced Heating of the Antiferromagnetic IrMn Layer on Generation of Terahertz Pulses in Co/WSe2-Based Spintronic Emitters

Effect of Laser-Induced Heating of the Antiferromagnetic IrMn Layer on Generation of Terahertz Pulses in Co/WSe2-Based Spintronic Emitters

Laser-Induced photothermal activation of multilayer MoS2 with spatially controlled catalytic activity

This study investigates the effects of high-power laser irradiation on multilayer MoS2, a promising material for catalysis, optoelectronics, and energy applications. In addition to previously reported sculpting of MoS2 layers, we discovered a novel effect of laser-induced photothermal heating that drives the chemical activation of MoS2. The photothermal effect was confirmed by temperature-dependent experiments, in situ temperature measurements with nanolocalized probes, and simulations. Remarkably, we observed the reduction of Ag+ ions on laser-irradiated MoS2 layers, forming plasmonic nanostructures without external stimuli such as photons or chemical reducing agents. We attribute this phenomenon to the significant defect density within the laser-carved region and the surrounding area induced by photothermal effects. Further functionalization of the laser-modified MoS2 with 4-nitrobenzenethiol self-assembled monolayers demonstrated a significant increase in photocatalytic activity, close to 100% yield compared to the negligible activity of pristine material. Our findings contribute to a deeper understanding of the light-induced modification of MoS2 properties and introduce a novel method for spatially controlling the chemical activation of MoS2. This advancement holds significant potential in developing high-performance 2D semiconductors as nano-engineered catalytic materials.

Intense femtosecond optical pulse shaping approaches to spatiotemporal control.

For studying any event, measurement can never be enough; "control" is required. This means mere passive tracking of the event is insufficient and being able to manipulate it is necessary. To maximize this capability to exert control and manipulate, both spatial and temporal domains need to be jointly accounted for, which has remained an intractable problem at microscopic scales. Simultaneous control of dynamics and position of an observable event requires a holistic combination of spatial and temporal control principles, which gives rise to the field of spatiotemporal control. For this, we present a novel femtosecond pulse-shaping approach. We explain how to achieve spatiotemporal control by spatially manipulating the system through trapping and subsequently or simultaneously exerting temporal control using shaped femtosecond pulses. By leveraging ultrafast femtosecond lasers, the prospect of having temporal control of molecular dynamics increases, and it becomes possible to circumvent the relaxation processes at microscopic timescales. Optical trapping is an exemplary demonstration of spatial control that results in the immobilization of microscopic objects with radiation pressure from a tightly focused laser beam. Conventional single-beam optical tweezers use continuous-wave (CW) lasers for achieving spatial control through photon fluxes, but these lack temporal control knobs. We use a femtosecond high repetition rate (HRR) pulsed laser to bypass this lack of dynamical control in the time domain for optical trapping studies. From a technological viewpoint, the high photon flux requirement of stable optical tweezers necessitates femtosecond pulse shaping at HRR, which has been a barrier until the recent Megahertz pulse shaping developments. Finally, recognizing the theoretical distinction between tweezers with femtosecond pulses and CW lasers is of paramount interest. Non-linear optical (NLO) interactions must be included prima facie to understand pulsed laser tweezers in areas where they excel, like the two-photon-fluorescence-based detection. We show that our theoretical model can holistically address the common drawback of all tweezers. We are able to mitigate the effects of laser-induced heating by balancing this with femtosecond laser-induced NLO effects. An interesting side-product of HRR femtosecond-laser-induced thermal lens is the development of femtosecond thermal lens spectroscopy (FTLS) and its ability to provide sensitive molecular detection.

Light-Induced Raman Spectra Oscillations and Macroscopic Propulsion of Graphene Bubbles

Atomically thin graphene bubbles can form on a flat substrate due to trapped substances between graphene and the substrate, providing an impressive case to study the intriguing properties of graphene with a nanoscale curvature. The energy balance between the van der Waals interaction of graphene to the substrate and the elastic energy required to deform graphene determines the shape, size, and internal pressure of the graphene bubble. In this work, light interference-induced Newton rings were clearly resolved not only in optical microscopy images but also in Raman spectroscopy maps of the graphene bubble, which originated from the optical standing waves formed in the graphene/SiO2/Si microcavity. Importantly, for the first time, such optical standing waves were directly visualized by imaging the spatial temperature distribution of laser-irradiated graphene bubbles through Raman scan mapping. Raman spectra oscillations can be explained by the laser-induced local heating effect and nonuniform temperature on the surface of the graphene bubble. Furthermore, with a higher laser power of illumination, a direct light propulsion of the bubble was observed on a macroscopic scale. The trajectory of the graphene bubble movement can be effectively manipulated by controlling the position and travel direction of the laser beam. These results offer an exciting opportunity to tune the optoelectronic properties of graphene and other two-dimensional materials at nanoscale confinement and to achieve the direct light manipulation of matter.

Laser-induced heating of polydimethylsiloxane-magnetite nanocomposites for hyperthermic inhibition of triple-negative breast cancer cell proliferation.

This paper presents the results of an experimental and computational study of the effects of laser-induced heating provided by magnetite nanocomposite structures that are being developed for the localized hyperthermic treatment of triple-negative breast cancer. Magnetite nanoparticle-reinforced polydimethylsiloxane (PDMS) nanocomposites were fabricated with weight percentages of 1%, 5%, and 10% magnetite nanoparticles. The nanocomposites were exposed to incident Near Infrared (NIR) laser beams with well-controlled powers. The laser-induced heating is explored in: (i) heating liquid media (deionized water and cell growth media [Leibovitz L15+]) to characterize the photothermal properties of the nanocomposites, (ii) in vitro experiments that explore the effects of localized heating on triple-negative breast cancer cells, and (iii) experiments in which the laser beams penetrate through chicken tissue to heat up nanocomposite samples embedded at different depths beneath the chicken skin. The resulting plasmonic laser-induced heating is explained using composite theories and heat transport models. The results show that the laser/nanocomposite interactions decrease the viability of triple-negative breast cancer cells (MDA-MB-231) at temperatures in the hyperthermia domain between 41 and 44°C. Laser irradiation did not cause any observed physical damage to the chicken tissue. The potential in vivo performance of the PDMS nanocomposites was also investigated using computational finite element models of the effects of laser/magnetite nanocomposite interactions on the temperatures and thermal doses experienced by tissues that surround the nanocomposite devices. The implications of the results are then discussed for the development of implantable nanocomposite devices for localized treatment of triple-negative breast cancer tissue via hyperthermia.

Measurement of Variations in Gas Refractive Index with 10-9 Resolution Using Laser Speckle.

Highly resolved determination of refractive index is vital in fields ranging from biosensing through to laser range finding. Laser speckle is known to be a sensitive probe of the properties of the light and the environment, but to date speckle-based refractive index measurements have been restricted to 10–6 resolution. In this work we identify a strategy to optimize the sensitivity of speckle to refractive index changes, namely, by maximizing the width of the distribution of optical path lengths in the medium. We show that this can be realized experimentally by encapsulating the medium of interest within an integrating sphere. While mitigating against laser-induced heating effects, we demonstrate that variations of the refractive index of air as small as 4.5 × 10–9 can be resolved with an uncertainty of 7 × 10–10. This is an improvement of 3 orders of magnitude when compared to previous speckle-based methods.

Sensing the Anti-Epileptic Drug Perampanel with Paper-Based Spinning SERS Substrates.

The applications of SERS in therapeutic drug monitoring, or other fields of analytical chemistry, require the availability of sensitive sensors and experimental approaches that can be implemented in affordable ways. In this contribution, we show the production of cost-effective SERS sensors obtained by depositing Lee-Meisel Ag colloids on filter paper either by natural sedimentation or centrifugation. We have characterized the morphological and plasmonic features of the sensors by optical microscopy, SEM, and UV-Vis spectroscopy. Such sensors can be used to quantify by SERS the anti-epileptic drug Perampanel (in the concentration range 1 × 10−4–5 × 10−6 M) by spinning them during the micro-Raman measurements on the top of a custom device obtained from spare part hard disk drives. This approach minimizes laser-induced heating effects and allows averaging over the spatial non-uniformity of the sensor.

Near-infrared emitting Nd3+-Yb3+ codoped Y2O3 nanocrystals for highly sensitive optical thermometry

Rare earth ions activated nanomaterials have been extensively considered as promising candidates for optical thermometry due to their unique photoluminescence characteristics. Nevertheless, thermally coupled levels-based thermometers are suffering from low sensitivity because of the restriction of small energy gap. Herein, the phonon-assisted energy transfer from Yb3+ to Nd3+ in Y2O3 nanoparticles, which makes the near infrared emissions of Nd3+ and Yb3+ ions respond to temperature inversely, is utilized to achieve sensitive temperature measurement via the ratiometric method. When pumped by 980 nm continuous wave laser, the multizone thermometry is performed owing to the different dependence of energy transfer on the temperature. The maximum relative sensitivities achieved in the temperature ranges of 423–773 K and 303–333 K are both approximately 2.3% K−1, which are superior to most previously reported luminescence-based temperature sensors. In addition, it is found that the measurement sensitivity is significantly influenced by the laser-induced heating effect especially at relatively low temperatures. Under the excitation of 980 nm square wave laser, the relative sensitivity is enhanced from 2.3% to 2.9% K−1 in the physiological temperature region. These findings can provide an effective pathway to improving the thermometric behavior and expanding the application of luminescence temperature sensing in various fields.

Formation of a Calcium Phosphate Layer with Immobilized Cobalt Chromite Nanoparticles on Cobalt−Chromium Alloy by a Laser-Assisted Biomimetic Process

The biocompatibility and osteoconductivity of metallic biomaterials can be achieved by calcium phosphate (CaP) coating. We recently developed a laser-assisted biomimetic (LAB) process for rapid and area-specific CaP coating on several materials. In the present study, the LAB process was applied to cobalt–chromium (Co−Cr) alloy, a metallic biomaterial widely used in orthopedic and dental applications. The LAB process was conducted by irradiation of unfocused pulsed laser light onto the substrate immersed in supersaturated CaP solution. The LAB-processed substrate formed CaP on the irradiated surface within only 5 min and was coated with a micron-thick CaP layer within 30 min by the effects of laser-induced surface modification and heating. Ultrastructural analysis with transmission electron microscopy revealed that the resultant CaP layer was integrated with the underlying substrate through two intermediate layers, an upper chromium oxide layer and a lower Co-rich (Cr-deficient) alloy layer. The CaP layer was loaded with a large number of cobalt chromite (CoCr2O4) nanoparticles. The results obtained offer new insights into the mechanism of CaP coating in the LAB process and future applications of LAB-processed Co−Cr alloys.

Laser assisted microfluidic membrane evaporator for sample crystallization separation

Microfluidic devices for sample crystallization separation plays crucially important role in various on-chip analytical and testing scenes. Evaporation-based microfluidic crystallization technology is one of the most important methods for on-chip sample enrichment and crystallization separation. However, the solvent evaporation process in closed chip device is severely limited by poor vapor transportation, unstable interfacial behaviors and low evaporation rate. Aiming to address these issues, here we designed a microfluidic membrane evaporator for fast continuous flow sample crystallization separation. In this design, laser induced heating effect was employed to trigger the evaporation of the solvent, gas-permeable hydrophobic polytetrafluoroethylene membrane was used to stabilize the gas-liquid interface and provide vapor pathways during the evaporation process. Effects of laser power, solution flow rate and sample concentration on the crystallization separation performance was investigated. Results indicates the designed microfluidic membrane evaporator has good crystallization separation performance under different operation conditions, which can be further applied to different types of microfluidic systems and platforms for on-chip analysis and testing.

Numerical modeling of laser-induced heating effect in optical thermometry

The laser-induced heating effect leads to obvious inaccuracy in optical thermometry, since this heating effect adjusts the fluorescence intensity ratio from two adjacent thermally coupled energy levels, and is difficult to measure with some equipment. It is necessary to accurately evaluate this heating effect and understand its formation mechanism. To overcome this problem, a 3D heat transfer model was developed by using finite element methods. Three physical processes are considered in this work: energy absorption from CW or pulsed lasers, heat conduction inside the matrix materials and heat transfer to the ambient air. It was found that the heating effect induced by lasers is dependent on the pump power and the spot radii of the lasers. Higher laser power and a narrower laser spot led to greater heat energy, resulting in higher temperatures. A fairly high temperature increment of 25.60 K was observed when a CW laser was used as an excitation source. The excitation modes of the laser also affect the heating effect. The thermal effect was suppressed by using a pulsed laser due to its shorter interaction time; however, it still cannot be ignored in the application of optical temperature sensors.

Dependence of the luminescent properties of thermostabilized upconversion NaYF4:Yb, Er particles on the excitation power and temperature

The excitation power dependence of upconversion luminescence intensity and temperature sensing characteristics are investigated in the NaYF4 : Er3 + , Yb3 + @ SiO2 particles synthesized in-house using a hydrothermal method. The effect of laser-induced heating of the upconversion particles is shown, which introduces distortions in the measured power and temperature dependences of the upconversion luminescence. We propose a technique for calibrating the temperature dependence of upconversion particle luminescence, which should improve the accuracy of temperature measurements. The technique is based on the stabilization of upconversion particles temperature, which provides the suppression of laser-induced heating of upconversion particles.

Upconversion photoluminescence and dual-mode temperature sensing properties of PIN-PMN-PT:Er3+ ceramic

Er3+ doped PIN-PMN-PT (PIN-PMN-PT:Er3+) ceramic was synthesized by two step columbite precursor method. The structure and morphology of products are characterized by X-Ray diffraction (XRD) and scanning electron microscopy (SEM). It is demonstrated that the ceramic has the perovskite structure and grain size in the range of 3 μm–5 μm. Under excitation of 980 nm diode laser, obvious green and red emission bands were detected. According to the power dependent upconversion emission and energy level diagram, the possible energy transfer process was proposed. The optical temperature sensing properties were studied based on fluorescence intensity ratios (FIRs) from thermal coupled energy levels (TCELs) 2H11/2,4S3/2 and thermal linked red emission stark sublevels 4F9/2(1), 4F9/2(2) of Er3+ ions. respectively. The absolute sensitivity reaches maximum value of 0.0035 K−1 at 360 K corresponding to TCELs and 0.0025 K−1 at 327 K corresponding to stark sublevels in the measurement temperature range. The incident near-infrared laser induced heating effects were investigated. It is found that the pump power induced heating effect can be neglected in the range of 110 mW–460 mW. These results demonstrated that PIN-PMN-PT:Er3+ ceramic is a potential material for application in optical temperature sensing and this research pave the way for further developing ceramic based dual-mode FIR thermometry technique.

Comprehensive Study on the Combined Effect of Laser-Induced Heating and Laser Power Dependence on Luminescence Ratiometric Thermometry.

Luminescence ratiometric thermometry, on the basis of nonthermally linked states of lanthanides, became a hot research issue recently because of its several attractive features. Here, the 5F4,5S2/5F5–5I8 transitions of Ho3+ embedded in calcium tungstate host are taken as an example to show the influence of laser pump power on this temperature detection technology. The luminescence intensity ratio between the 5F4,5S2/5F5–5I8 upconversion emission lines was found to respond monotonously to the temperature between 303 and 603 K and could be fitted well with the use of an empirical function. It suggested that this ratio might be suitable for temperature measurement. However, at 303 K, the temperature readout derived from this ratio decreased from 303 to 248 K on increasing the laser pump power from 35 to 205 mW (the irradiated spot’s area: ca. 2 mm2). This uncommon phenomenon differs from the conventional laser-induced heating effect. With the help of the Boltzmann distribution based on the two Stark components of the 5F5 state of Ho3+, the laser-induced heating was calculated to be ca. 20 K when the excitation power was 205 mW. Thus, this suggested that there should be a mechanism responsible for the gradually decreasing temperature readout. It was then confirmed that this mechanism was the different dependences for the 5F4,5S2/5F5–5I8 transitions on laser pump power, which was much stronger than the laser-induced heating effect. A calibration method to eliminate the influence of laser power dependence on luminescence ratiometric thermometry was then proposed.

Raman microspectroscopy of PuO2 particulate aggregates

Raman microspectroscopy is a useful technique with the capability to infer local physical properties of materials such as crystalline order. Crystalline order and morphology of plutonium dioxide (PuO2) grains and aggregates are known to be sensitive to the initial production conditions and represent the baseline for understanding subsequent signatures. PuO2 samples were synthesized and then characterized by scanning electron microscopy prior to Raman analysis. A total of nine laser excitation wavelengths (785, 633, 561, 514, 488, 457, 405, 325 and 244 nm) were evaluated to maximize signal and minimize fluorescence, with 514 nm selected for most subsequent work. The effect of laser-induced heating and annealing on the Raman spectra were investigated with a 514 nm laser beam. The ratio of the Stokes and anti-Stokes band intensities was used to estimate the temperature during the laser-induced heating process. The band position and the band full-width at half-maximum (FWHM) were used to track the degree of sample annealing at an estimated temperature. The Raman spectra showed that laser-induced annealing resulted in significant enhancement of the intensity for most spectral bands. Similarly, the FWHM of most bands decreased with increasing annealing temperature. The largest Raman shift of the T2g band for an annealed sample was measured at 480 cm−1. A new, sharp band at 1047 cm−1 emerged during the material annealing process and the intensity grew proportional to the intensity of the T2g band. Crystal Field Theory computational analysis suggests the 1047 cm−1 band is the long sought Γ1 → Γ4 electronic transition proposed by several researchers. The data acquired in this work helps to explain the variability in band position and FWHM reported in the literature, including the assignment of new weak bands associated with Raman resonance and Raman electronic transitions.

Influence of excitation power and doping concentration on the upconversion emission and optical temperature sensing behavior of Er3+: BaGd2(MoO4)4 phosphors

Generally, the effects of excitation power and dopant concentration on the optical temperature sensing behaviors of rare earth (RE) doped materials based on the fluorescence intensity ratio (FIR) technique are disregarded. In this paper, Er3+: BaGd2(MoO4)4 phosphors with different concentrations were fabricated by the high temperature solid-state reaction method. The results show that the variation of FIR (2H11/2/4S3/2) with excitation power is not only related to the laser-induced heating effect, but also the diverse power-dependences of 2H11/2 and 4S3/2 levels. Consequently, the temperature calibration curves change at different excitation power densities. When the calibration curve obtained at a low power density is applied to estimate the temperature of the object excited at a high power density, a large overestimate of the temperature rise induced by the optical heating effect can be caused. Besides, the temperature sensing sensitivity depends on the Er3+ doping concentration, which increases first with concentration to a maximum and then reduces. The maximal absolute sensitivity is ~110.5 × 10−4 K−1 in 5mol% Er3+: BaGd2(MoO4)4 phosphor, which is among the highest values of RE ions doped phosphors based on thermally coupled levels recorded before.

Investigation on laser-induced heating in NaYbF4:Er3+ for accurate photo-thermal conversion with temperature feedback

The laser-induced local heating effect under the irradiation of 980 nm near-infrared laser was investigated in NaYbF4:Er3+ with the upconversion emission intensity ratio of Er3+ as a real-time temperature probe. Under the excitation power density of 9.1 W/cm2 the temperature of the irradiated sample can increase from room temperature to about 580 K in 5 s, indicating that NaYbF4:Er3+ could be an efficient heat source for accurate photo-thermal conversion with temperature feedback, which may be applied in photo-thermal therapy, drug release, etc. The result also shows that the dependence of upconversion emission intensity of Er3+ ions on power density of pump laser is time-related, the saturation of upconversion emission is very obvious for steady state irradiation while the saturation is not observed at the beginning of irradiation, implying that the saturation of upconversion emission is mainly caused by the thermal quenching at high temperature induced by laser irradiation with high power density.

Up-conversion luminescence, temperature sensing properties and laser-induced heating effect of Er3+/Yb3+ co-doped YNbO4 phosphors under 1550 nm excitation

YNbO4 phosphors with various Er3+ and Yb3+ concentrations were synthesized via a traditional high-temperature solid-state reaction method. Their crystal structure was investigated by means of X-ray diffraction (XRD) and Rietveld refinements, and it was confirmed that the obtained samples exist in monoclinic phase. The Er3+ and Yb3+ concentration-dependent up-conversion (UC) luminescence was studied under 1550 nm excitation. By inspecting the dependence of UC intensity on the laser working current, it was found that four-photon and three-photon population processes were co-existent for generating the green UC emissions in the samples with higher Yb3+ concentrations. In addition, it was observed that the temperature sensing properties of YNbO4: Er3+/Yb3+ phosphors were sensitive to both Er3+ and Yb3+ doping concentrations. Furthermore, based on the obtained temperature response of the UC luminescence phosphors, 1550 nm laser-irradiation-induced thermal effect was studied, and it was discovered that the sample temperature was very sensitive to the doping concentrations of Er3+ and Yb3+ and the excitation power.

Dependence of optical temperature sensing and photo-thermal conversion on particle size and excitation wavelength in β-NaYF4:Yb3+, Er3+ nanoparticles

Hexagonal-phase NaYF4:Yb3+, Er3+ upconversion nanoparticles (UCNPs) have been widely studied as temperature sensors and photothermal nanomaterials in bioscience. In this work, β-NaYF4:Yb3+, Er3+ UCNPs were synthesized via a thermal decomposition method. Particle size and excitation wavelength dependent temperature sensing properties were studied according to the temperature dependent emission spectra and fluorescence intensity ratio (FIR) technique. It was found that particle sizes (21.6 nm and 64.3 nm) and excitation wavelengths (980 nm and 1550 nm) almost have no effect on the temperature sensing properties of β-NaYF4:Yb3+, Er3+ UCNPs. In addition, the laser-induced heating effect on the samples with different sizes under different excitation wavelengths were also investigated. It was deduced that the sample temperature was very sensitive to the laser excitation density, excitation wavelength and particle size. The samples reached higher temperature with higher laser excitation density and shorter excitation wavelength. With the same excitation wavelength and excitation density, the larger particle size of β-NaYF4:Yb3+, Er3+ UCNPs (63.4 nm) generated much more heat than that of the smaller UCNPs (21.6 nm).

The beam coherence simulation of 1-dimensional nano-scale photocathode under high power laser irradiation

1-dimensional (1D) nano-scale photocathode with back-illumination is a promising technology for producing highly coherent electrons which may allow us to realize 4-dimensional space-time analysis of atomic structures. By simulation, we evaluated the coherence of electrons generated from gold cathode by taking into account laser-induced heating effect. The laser irradiation conditions for different cathode thickness were derived from 1D-Two Temperature Model (TTM). We also investigated the coherence of the beam by beam tracking simulation including conventional extracting electric field. Our result indicates that the beam coherence at the acceleration electron where the sample to measure is located is not sensitive to the initial beam coherence on the cathode surface.