Application Of Laser Pulses Research Articles

SURG-49. INVESTIGATING LITT-BASED COMBINATION THERAPIES IN PRECLINICAL GLIOMA MODELS

Abstract BACKGROUND Laser interstitial thermal therapy (LITT) is a minimally invasive means of tumor cyto-destruction with the potential for additional clinical benefits, such as altering the blood-brain barrier or the brain tumor microenvironment (TME). Using a murine model of GBM, we utilized a clinically relevant laser ablation model to identify and exploit immune TME changes after LITT to generate therapies that improve mouse survival, with the potential for rapid clinical translation. METHODS Right frontal lobe implantation of the immune “cold” SB28 murine glioma cells were performed in C57BL/6J mice. Tumor location was verified by MRI followed by stereotactic insertion of a paired fiberoptic laser and thermocouple to perform real-time hyperthermic ablation with temperature monitoring. Pulsed laser application maintained a peri-lesional temperature of 44°C for 150-180 seconds. Following LITT (or sham surgery), spectral flow cytometry was used to profile the immune TME. Survival studies were performed using a combination of LITT and immune modulating therapies. RESULTS Laser ablation alone provided a survival benefit compared to sham surgery (median survival: 29 vs 22.5 days, P<0.0001) in in glioma-bearing mice. Survival studies combining LITT with anti-PD1 lacked a significant response in the SB28 model but showed some long-term survivors. Flow cytometry performed on brain tissue post-LITT days 3 and 7 demonstrated little to no change in CD4+/CD8+ T cell responses but did show an increase in neutrophils, which expressed TLR2 and 4. The TME showed negligible numbers of phagocytic cells with obvious tumor cell uptake post-LITT. Using these results, we generated strategies for LITT-based combination immune therapies. Survival studies are ongoing using combinations of LITT/anti-PD1 with neutrophil depletion, inhibition of anti-CD47, and addition of broad TLR2/4 agonists as a neutrophil stimulus. CONCLUSIONS A clinically relevant immunocompetent murine LITT model enables the generation of novel treatment strategies with potential for rapid clinical translation.

Deciphering the Nd3+ environment and energy-transfer mechanisms in thermally stable novel calcium aluminate glasses: elucidation of broadband high-gain performance for laser applications

Rare-earth-doped barium calcium aluminate (BCA) glasses, having extended infrared (IR) transmission (6 μm), are attractive materials for near IR (NIR) photonic applications. Nd2O3-doped BCA glasses display broadband emission at 1.07 µm, but they are limited, with poor glass-forming ability (GFA) and low emission cross sections. In the present study, four different barium zinc calcium aluminate (BZCA) glasses are synthesized with varied ZnO concentrations (from 9.5 to 24.5 mol%) and doped with 0.5 mol% Nd2O3 to decipher the effect on GFA and spectroscopic properties. The addition of ZnO enhances the GFA, and the NdBZCA20 glass shows the maximum GFA. Ultraviolet (UV)–visible (Vis)–NIR absorption spectra reveal a decreasing trend in the nephelauxetic effect, while J–O parameters, emission, and gain properties lead to no significant alteration with increasing ZnO, and the structure–properties correlation is established accordingly. However, the emission cross sections for all ZnO concentrations are found ∼4.5 × 10−20 cm2 accompanied by broadband emission (Δλ eff ∼ 40 nm), which ensures the potentiality of these glasses for low-threshold high-gain laser applications as well as ultrashort pulse laser applications. Furthermore, a thorough analysis of 1.06 µm emission as a function of Nd concentration in the BZCA20 glass is reported here. The emission spectra and decay time indicate that 0.5 mol% is the optimized doping concentration. Inokuti–Hirayama and Burshtein equations are adopted to study the decay kinetics and energy-transfer mechanisms, which confirm that the energy-transfer process due to cross-relaxation is dominant up to 0.5 mol% concentration, whereas, beyond that concentration, excitation energy migration via the hopping mechanism supersedes.

Growth and Characterization of Yb: CALYGLO Crystal for Ultrashort Pulse Laser Applications

Yb:CALYGLO crystals with a dopant concentration of 5 at.% were successfully grown using the Czochralski method. The crystal samples were extensively studied to analyze their structure, room temperature and low temperature spectra, and laser properties. The highest absorption cross-section at 977 nm was calculated to be 1.83 × 10−20 cm2 for σ polarization and 5.32 × 10−20 cm2 for π polarization. Similarly, the emission cross-section was determined to be 1.38 × 10−20 cm2 at 980 nm for σ polarization and 2.28 × 10−20 cm2 at 981 nm for π polarization, with a full width at half maximum (FWHM) of 50.3 nm and 89.5 nm, respectively. The fluorescence lifetime of the 5 at.% Yb:CALYGLO crystal at 2F5/2 was measured to be 1.10 ms. Additionally, gain cross-sections were calculated for different β values. In the continuous laser experiment, the crystal demonstrated a laser output of 20.15 W at 1057 nm, with a slope efficiency of 53.3%. These experimental findings indicate that the lattice of Y3+ in the crystal is partially replaced by Lu3+ and Gd3+, resulting in a broader spectrum. Consequently, this crystal shows promising potential as a gain medium for ultrashort pulse laser crystals.

Femtosecond pulsed laser technology and applications

This paper describes femtosecond pulsed laser technology and related applications. The focus is on two core femtosecond pulsed laser technologies: femtosecond pulsed laser generation and amplification. In the generation of femtosecond pulsed lasers, mode-locking techniques, Kerr-lens mode-locking, and semiconductor saturable absorber mirrors are presented; in the amplification of femtosecond pulsed lasers, chirped-pulse amplification and coherent synthesis techniques are presented. This paper analyses the applications of femtosecond pulsed lasers in both the biomedical and manufacturing sectors and gives the development trends as well as the challenges of femtosecond laser technology. Femtosecond lasers are now used in a wide range of applications. Femtosecond pulsed lasers will develop in the directions of high power, miniaturisation, intelligence and precision. Laser tweezers will become the new direction of development in the future.

The growth and spectroscopic properties of Yb:KNGM crystal: A promising ultrashort pulse laser material

Yb3+-doped mixed laser crystals are widely recognized as materials capable of generating ultrashort pulses and have garnered significant attention in recent times. In this study, we thoroughly examined the structure and spectroscopic properties of a novel mixed molybdate crystal, Yb:KNGM. Notably, we made detailed observations of an exceptionally broad absorption band with a full width at half maximum (FWHM) of 78 nm. The broad absorption band indicates that the commercially available InGaAs laser diode (LD) can be effectively utilized for high pumping efficiency purpose. The absorption and emission cross-section at 967 and 1014 nm were calculated to be 1.56 × 10−20 cm2 and 2.05 × 10−20 cm2, respectively. The FWHM of the emission band reaches a substantial range of 62 nm, making it highly conducive to the production of ultrashort pulse lasers. The bandgap (Eg) was fitted as 3.26 eV by Tauc formula. Positive gain cross-section can be achieved while the β is only higher than 0.2 and a large FWHM of 41 nm was discovered when β is 0.5. The aforementioned merits provide compelling evidence that Yb:KNGM crystal holds great promise as a laser crystal for the application of wild tunable and ultrashort pulse lasers pumped by LD.

All-Fiber Narrow-Bandwidth Mode-Locked Laser Based on Polarization-Dependent Helical Long-Period Grating

As a crucial component of nonlinear polarization rotation (NPR) mode locking, optical fiber gratings offer advantages such as polarization modulation capability, stability, fiber compatibility, and preparation maturity, making them a vital technological foundation for achieving NPR mode locking. Here, a polarization-maintaining fiber helical long-period grating (PMF-HLPG) was designed and fabricated as a polarizer using the CO2-laser direct-write technique to realize the NPR effect. A homemade fiber Bragg grating (FBG) was also introduced into the laser system to enable a narrow-bandwidth lasing output and wavelength tunability. Based on the PMF-HLPG and FBG mentioned above, an all-fiber mode-locked laser with a spectra bandwidth of 0.15 nm was constructed to generate stable short pulses with a fundamental repetition rate of 12.7122 MHz and a pulse duration of 30.08 ps. In particular, its signal-to-noise ratio is up to 84.5 dB, showing the high stability of the laser. Further, the operating wavelength of the laser can be tuned from 1559.65 nm to 1560.29 nm via heating the FBG while maintaining its mode-locked state with stability. The results indicate that the PMF-HLPG could be used as a polarizer to meet the NPR mechanism for ultrashort pulse laser applications in optical communication, optical sensing, and biomedical imaging.

Nonlinear-Compensation High-Uniformity Pulsed Bessel Beam in the Transparent Material

Ultrashort pulse Bessel beams have gained attention for their ability to process high aspect ratio structures with precision drilling and cutting. However, focusing the beam inside transparent materials can lead to local stretching or compression due to material-air interface mismatch and nonlinear absorption, causing issues with uniformity of focus and processing depth. In this study, we propose a nonlinear compensation scheme for femtosecond pulsed Bessel beam stretching that modulates the optical phase of the pulse beam ring, achieving high-uniformity longitudinal distribution. This scheme enabled the creation of a highly uniform damaged structure measuring 540 μm in length and with a width standard deviation of only 145 nm inside fused silica. Our findings offer a new solution for ultrashort pulse laser applications in high aspect ratio drilling and fast precision cutting of transparent materials.

Optical and luminescence studies of Nd3+ doped phosphate glasses for pulsed laser applications

A series of glass with appropriate chemical compositions (60-x) P2O5 + 20 Bi2O3 + 10 SrF2 + 10 Na2 CO3 + x Nd2O3, (x = 0.1, 0.5, 1.0, 1.5, and 2.0% by mole) were prepared by using the melt quenching technique. The glass phase structure was confirmed by using X-ray diffraction technique. The structural analysis using FTIR technique it reveals characteristic bonding vibrations and different functional group in the glass matrix. The elements present in the fabricated glass sample was analyzed by using EADX spectrum. J-O intensity parameters Ω2, Ω4, and Ω6for the currently being researched PBNSNd10 glass have values of 9.80 × 10-20 cm2, 3.305 × 10-20 cm2, and 5.576 × 10-20 cm2 sequentially. The J-O parameters shows a trend of Ω2 > Ω6 > Ω4. The near infrared emission spectra recorded with 808 nm laser diode excitation for various concentrations of neodymium ions show the emission intensity is highest for the 4F3/2 → 4I11/2 transition at 1056 nm. The measured decay times 4F3/2 level decreased with increasing Nd2O3 ions because of concentration quenching effect. The obtained results in present study have been compared with previous results obtained for Nd2O3 doped glasses.

Pulsed thulium laser blood vessel haemostasis as an alternative to bipolar forceps during neurosurgical tumour resection

Due to wavelength-specific water absorption, infrared lasers like the thulium laser emitting at 1940 nm wavelength proved to be suitable for coagulation in neurosurgery. Commonly bipolar forceps used for intraoperative haemostasis can cause mechanical and thermal tissue damage, whilst thulium laser can provide a tissue-gentle haemostasis through non-contact coagulation. The aim of this work is a less-damaging blood vessel coagulation by pulsed thulium laser radiation in comparison to standard bipolar forceps haemostasis. Ex vivo porcine blood vessels in brain tissue (0.34 ± 0.20 mm diameter) were irradiated in non-contact with a thulium laser in pulsed mode (1940 nm wavelength, 15 W power, 100–500 ms pulse duration), with a CO2 gas flow provided simultaneously at the distal fibre tip (5 L/min). In comparison, a bipolar forceps was used at various power levels (20–60 W). Tissue coagulation and ablation were evaluated by white light images and vessel occlusion was visualised by optical coherence tomography (OCT) B-scans at a wavelength of 1060 nm. Coagulation efficiency was calculated by means of the quotient of the difference between the coagulation and ablation radius to the coagulation radius. Pulsed laser application achieved blood vessel occlusion rate of 92% at low pulse duration of 200 ms with no occurrence of ablation (coagulation efficiency 100%). Bipolar forceps showed an occlusion rate of 100%, however resulted in tissue ablation. Tissue ablation depth with laser application is limited to 40 μm and by a factor of 10 less traumatising than with bipolar forceps. Pulsed thulium laser radiation achieved blood vessel haemostasis up to 0.3 mm in diameter without tissue ablation and has proven to be a tissue-gentle method compared to bipolar forceps.

CrPS4 Nanoflakes as Stable Direct-Band-Gap 2D Materials for Ultrafast Pulse Laser Applications

Two-dimensional (2D) materials have attracted considerable attention due to their potential for generating ultrafast pulsed lasers. Unfortunately, the poor stability of most layered 2D materials under air exposure leads to increased fabrication costs; this has limited their development for practical applications. In this paper, we describe the successful preparation of a novel, air-stable, and broadband saturable absorber (SA), the metal thiophosphate CrPS4, using a simple and cost-effective liquid exfoliation method. The van der Waals crystal structure of CrPS4 consists of chains of CrS6 units interconnected by phosphorus. In this study, we calculated the electronic band structures of CrPS4, revealing a direct band gap. The nonlinear saturable absorption properties, which were investigated using the P-scan technique at 1550 nm, revealed that CrPS4-SA had a modulation depth of 12.2% and a saturation intensity of 463 MW/cm2. Integration of the CrPS4-SA into Yb-doped fiber and Er-doped fiber laser cavities led to mode-locking for the first time, resulting in the shortest pulse durations of 298 ps and 500 fs at 1 and 1.5 µm, respectively. These results indicate that CrPS4 has great potential for broadband ultrafast photonic applications and could be developed into an excellent candidate for SA devices, providing new directions in the search for stable SA materials and for their design.

Electro-optic fs pulsed laser deflection in KTN crystals using UV illumination.

UV-illuminated, paraelectric-phased potassium tantalate niobate (KTN) single crystals mitigate the beam deformation effects of femtosecond pulsed lasers in KTN deflectors. UV light illumination can control the amount of trapped charge present and minimize domain inversion in KTN deflectors, owing to its generated electron-hole pairs. This enables high beam quality deflection of fs pulsed lasers, with access to larger deflection angles, deflection speeds, and modulation switching ratios. These results enable the use of KTN deflectors in many fs pulsed laser applications and hasten the advancement of fs applications that require these deflection qualities.

Preparation and pulsed fiber laser applications of emerging nanostructured materials

This review provides recent advances of preparation and pulsed fiber laser applications of emerging nanostructured materials. The preparation methods and applications of these materials as the saturable absorbers in pulsed fiber lasers are provided.

Dynamic Characteristics and Application of Pulsed CO2 Laser Induced Liquid Micro‐Jet

Dynamic Characteristics and Application of Pulsed CO2 Laser Induced Liquid Micro‐Jet

High-Current Operation of Racetrack-Shaped LTD Using SiC-MOSFETs for Pulsed Laser Applications

Pulsed power is widely used for the excitation of pulsed lasers, especially the ultraviolet excimer lasers. Experiments have been carried out to demonstrate the excitation of KrF excimer laser by using pulsed power generator based on linear transformer driver (LTD) <xref ref-type="bibr" rid="ref1" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">[1]</xref> . In this article, the LTD system has been upgraded by replacing the semiconductor switches with silicon carbide (SiC) devices in order to increase the output current and by reshaping the output interface so that it fits better with the geometry of the laser chamber. For excimer laser application, the output current and its rise time are very important issues. These are the focus points of the system design and performance analysis for this study. The experimental test system is described in detail and the results are presented with discussions on potential applications.

Giant saturation absorption of tungsten trioxide film prepared based on the seedless layer hydrothermal method

Nonlinear materials have gained wide interest as saturable absorbers and pulse compression for pulsed laser applications due to their unique optical properties. This work investigates the third-order nonlinear phenomenon of tungsten trioxide (WO3) thin films. The giant nonlinear absorption and nonlinear refractive index of WO3 thin films were characterized by Z-scan method at 800 nm. We experimentally observed the giant saturable absorption (SA) and nonlinear refractive index of WO3 thin films prepared by the seedless layer hydrothermal method, with SA coefficient being as high as –2.59 × 105 cm⋅GW−1. The SA coefficient is at least one order of magnitude larger than those of the conventional semiconductors. The nonlinear refractive index n 2 of WO3 film has been observed for the first time in recent studies and the corresponding coefficient can be up to 1.793 cm2⋅GW−1. The large third-order nonlinear optical (NLO) response enables WO3 thin films to be promising candidates for optoelectronic and photonic applications in the near-infrared domain.

Ambient-stable MXene with superior performance suitable for widespread applications

MXenes, as attractive two-dimensional materials, have shown extraordinary potential for applications, however, their instability severely limits further research and applications on a large-scale and industrial level. Here, we overcome the environmental instability of MXene-Ti3C2Tx by an optimized synthetic route, including the synthesis of high-quality MAX phase (Ti3AlC2) and the post-treatment of Ti3C2Tx. The optimized Ti3C2Tx (O-Ti3C2Tx) achieves a dramatic improvement in stability. Even at low concentrations (∼0.1 mg/mL), the dark green aqueous dispersion of monolayer O-Ti3C2Tx showed no oxidation and degradation when aged under ambient conditions for two months, while conventional Ti3C2Tx required only ∼ 10 days for complete oxidative degradation under the same conditions. More importantly, compared with the conventional Ti3C2Tx, O-Ti3C2Tx exhibits higher conductivity, better nonlinear optical properties, excellent thermal stability, and comparable biocompatibility. In the application of pulsed laser with MXene as a saturable absorber, the conventional Ti3C2Tx leads to severe degradation of Q-switching performance due to its instability, while O-Ti3C2Tx shows excellent Q-switching performance in long-term operation. This work achieves a substantial solution to the instability problem of MXene-Ti3C2Tx without compromising its excellent performance, paving the way for the development of its practical applications.

SiO2 passivated TaS2 saturable absorber mirrors for the ultrafast pulse generation

Since its inception as the cornerstone of the ultrafast pulse laser, semiconductor saturable absorber mirrors (SESAMs) have attracted considerable interest. Meanwhile, low-dimensional (LD) materials based saturable absorbers (SAs) are gaining popularity in pulsed laser applications due to their high nonlinearity, strong light-matter interaction, and low cost. Here, high-quality LD-SAs have been created by transferring 2 H-TaS 2 onto gold mirrors and covered with plasma-enhanced chemical vapor deposition (PECVD) SiO 2 layers. The non-linear transmission of SiO 2 passivated TaS 2 -SAM was measured using a balanced dual-detector technology. The modulation depth and saturated intensity were ~8.4% and 0.86 MW·cm −2 . Based on the SiO 2 passivated TaS 2 -SAM, Q-switched and mode-locked Erbium-doped (Er 3+ -doped) fiber pulse lasers have been successfully achieved. Stable soliton pulses are obtained in erbium-doped fiber lasers (EDFLs) with pulse width of 1.8 ps, repetition rate of 3.4 MHz and a center wavelength of 1560.6 nm. Moreover, the mode-locking laser exhibited long-term stability with high signal-to-noise ratio of 63 dB. This study serves as a standard for low-dimensional materials research in photonics applications, and the results reveal that TaS 2 -SAM has a wide range of applications in multifunctional all-fiber lasers.

PECVD-derived graphene saturable absorber mirror for 2.8 μm pulsed Er:ZBLAN fiber laser

Graphene has been emerging as an ideal mid-infrared saturable absorber (SA) due to its broadband absorption, ultrafast nonlinear optical response, high stability and thermal tolerance. However, the current routes (e.g. chemical vapor deposition and spin coating) for constructing graphene SAs are suffering from the limited flexibility in substrate choice and the introduction of impurities during the transfer process, resulting in poor film quality and unstable laser modulation. Here, we demonstrate a high-quality graphene SA mirror (GSAM) grown directly on calcium fluoride (CaF2) substrate by a low-temperature plasma enhanced chemical vapor deposition (PECVD) method for mid-infrared pulse modulation. The controllable growth of high-quality graphene film on the nickel-modified CaF2 substrate is realized by adjusting the growth time and hydrocarbon ratio during PECVD process. Consequently, the GSAM shows excellent nonlinear optical absorption with the modulation depth of 11.2%. By inserting the GSAM into the Er:ZBLAN fiber laser, a stable passive Q-switched (QS) operation can be achieved with an average output power of 142 mW and a pulse width of 300.2 ns. The slope efficiency of QS laser is up to 17.4% and the peak power is 7.76 W. Our strategy paves the way for developing high quality and modulation stability GSAM towards industrial applications of pulsed mid-infrared lasers.

Comparative study of GaAs nanostructures synthesized in air and distilled water by picosecond pulsed laser ablation and application in hazardous molecules detection

This work explored the fundamental differences/mechanisms between the GaAs substrates ablated in two different media of air and distilled water (DW). A scan area of 5 × 5 mm2 was ablated by a picosecond laser with a pulse duration of 30 ps, a repetition rate of 10 Hz, a wavelength of 1064 nm, and a pulse energy of 2 mJ. The spacing between raster scan lines was varied (0.05–0.35 mm), keeping the scan speed (0.15 mm/s) constant. The obtained GaAs nanostructures (NSs) were thoroughly analyzed using microscopy techniques. A clear increase in separation between the raster scan lines was observed with an increase in the scan spacing for the GaAs NSs fabricated in air, whereas the same result was not observed in DW. Moreover, structures with debris were formed in air irrespective of the spacing, unlike the formation of uniform quasiperiodic GaAs NSs throughout the sample in the case of DW ablation. To the best of our knowledge, there are no reports on the detailed studies involving DW in the fabrication of quasiperiodic NSs of GaAs. Further, these quasiperiodic GaAs NSs formed in DW were coated with a thin layer of gold using the thermal evaporation method, annealed at 400 °C for 1 h in an ambient atmosphere. As a consequence of annealing, Au NPs were uniformly decorated on the quasiperiodic NSs of GaAs imparting plasmonic nature to the whole structures. Subsequently, the Au NPs decorated GaAs NSs were utilized as surface enhanced Raman scattering substrates for the detection of methylene blue (dye molecule) and Thiram (pesticide molecule) at low concentrations.

2D layered MSe2 (M = Hf, Ti and Zr) for compact lasers: nonlinear optical properties and GHz lasing

Abstract Two-dimensional (2D) ternary transition-metal dichalcogenides (TMDCs) are of great research interest because their superior layer-dependent optical modulation properties. In this work, three different kinds of TMDC nanosheets, including hafnium diselenide (HfSe2), titanium diselenide (TiSe2) and zirconium diselenide (ZrSe2), are prepared by liquid phase exfoliation (LPE) technique. The high-quality material properties of these TMDC nanosheets are confirmed by Raman spectroscopy and X-ray diffraction analysis. Furthermore, the bandgap information of five-layer MSe2 has been investigated via utilizing density functional theory. The calculation results exhibit ultra-narrow bandgap structure (lower than 1.1 eV) for all these three materials, indicating that MSe2 is suitable for broadband photonic applications. By applying the fabricated MSe2 as saturable absorbers, high-performance Q-switched mode-locked laser operation has been realized. The laser gain media are Nd:GdVO4 cladding waveguides fabricated by femtosecond laser direct writing. As a result, the pulsed waveguide lasers are able to deliver approximately 6-GHz laser pulses with a signal-to-noise ratio of over 45 dB. The minimum pulse width is determined to be as short as 26 ps. The results demonstrated in this work exhibit the great potential of TMDCs and waveguide structures in applications of pulsed lasers with compact footprints.