Laser-induced Damage Threshold Value Research Articles

Exploring fs-laser irradiation damage subthreshold behavior of dielectric mirrors via electrical measurements

Abstract With ultrafast laser systems reaching presently 10 PW peak power or operating at high repetition rates, research towards ensuring the long-term, trouble-free performance of all laser-exposed optical components is critical. Our work is focused on providing insight into the optical material behavior at fluences below the standardized laser-induced damage threshold (LIDT) value by implementing a simultaneous dual analysis of surface emitted particles using a Langmuir probe (LP) and the target current (TC). ${\mathrm{HfO}}_2$ and ${\mathrm{ZrO}}_2$ thin films deposited on fused silica substrates by pulsed laser deposition at various ${\mathrm{O}}_2$ pressures for defect and stoichiometry control were irradiated by Gaussian, ultrashort laser pulses (800 nm, 10 Hz, 70 fs) in a wide range of fluences. Both TC and LP collected signals were in good agreement with the existing theoretical description of laser–matter interaction at an ultrashort time scale. Our approach for an in situ LIDT monitoring system provides measurable signals for below-threshold irradiation conditions that indicate the endurance limit of the optical surfaces in the single-shot energy scanning mode. The LIDT value extracted from the LP-TC system is in line with the multipulse statistical analysis done with ISO 21254-2:2011(E). The implementation of the LP and TC as on-shot diagnostic tools for optical components will have a significant impact on the reliability of next-generation ultrafast and high-power laser systems.

Growth, optical, morphological, thermal, laser induced damage threshold, microhardness properties of an organic novel single crystal: Piperazinium 2-Furoate

The novel organic crystal Piperazinium 2-Furoate (P2F) was created using the slow evaporation method. The solubility test for the P2F was determined by gravimetric analysis. The nucleation kinetics such as metastable zone width, induction period and interfacial energy has been calculated. The novel crystallographic parameters were determined, the crystal has a position in the triclinic system and the cell parameters found to be a = 6.30 Å, b = 6.88 Å, c = 17.46 Å. The UV–Vis spectrum was analyzed and the crystal has a cut-off wavelength of 267 nm. The bandgap energy from Tauc's plot was identified to be 4.64 eV, and other optical parameters like refractive index, extinction co-efficient etc., were calculated. The vibrational spectral studies was analyzed using FTIR and FT-Raman analysis. The thermal analysis confirmed that the P2F crystal has good thermal stability upto 261 °C. The yellow luminescence is produced at 572 nm in the fluorescence analysis. The laser induced damage threshold value of the P2F crystal is 1.889 GW/cm2. The mechanical stability of the grown crystal was tested and it shows that the crystal belongs to soft material category. The EDX analysis confirmed the well combination of the crystal compound. The P2F's SEM micrographs confirmed that it has a micro-sized range irregular oval shaped and an uneven distribution. The nonlinear optical (NLO) property of P2F crystal confirm its suitability for higher order nonlinear optical applications.

Crystal structure, electronic structure, and optical properties of Cu4ZnGe2S7 and Cu4CdGe2S7: Polar diamond-like semiconductors exhibiting second harmonic generation

The novel I4-II-IV2-VI7 quaternary diamond-like semiconductors (DLSs), Cu4ZnGe2S7 and Cu4CdGe2S7, were prepared from the constituent elemental powders at elevated temperatures. Cu4ZnGe2S7 crystallizes in the polar, chiral space group C2 and adopts the Cu4NiSi2S7 structure-type, which can be considered a derivative of the cubic diamond structure. The cadmium analog takes on the Cu5Si2S7 structure-type, which is related to the hexagonal diamond structure, and displays polar, Cc space group symmetry. Both compounds contain [Ge2S7]6- anions created by corner-sharing GeS4 tetrahedra. The crystal structures were carefully evaluated using: 1) extended connectivity tables, 2) minimum bounding ellipsoid analysis, and 3) bond valence sum (BVS) and global instability index (G) calculations. Both compounds are thermally stable up to temperatures exceeding 950 °C and melt incongruently. As assessed using diffuse reflectance spectroscopy, Cu4ZnGe2S7 and Cu4CdGe2S7 possess optical bandgaps of 1.65 eV and 1.90 eV, respectively, which are narrower than the analogous I2-II-IV-VI4 DLSs. Electronic structure calculations show that both compounds are direct-bandgap semiconductors with significant contributions of Cu-d and S-p orbitals to the states at the top of the valence band. While Cu4CdGe2S7 displays a weak second harmonic generation (SHG) response, the second-order nonlinear optical susceptibility, χ(2), of Cu4ZnGe2S7 is 14.8 ± 1.5 pm V-1, assessed using the Kurtz-Perry powder method and an optical-grade AgGaSe2 (AGSe) reference. Both compounds exhibit laser-induced damage threshold values similar to AGSe, ∼0.1 GW cm-2, for λ = 1.064 µm using picosecond laser pulses. Most importantly, Cu4ZnGe2S7 exhibits a phase-matching behavior at λ = 3.1 µm. These results suggest that Cu4ZnGe2S7 holds potential for use in low-powered laser applications involving efficient wave mixing in the mid-IR region.

Ce(IO3)3F and Ce(IO3)2(NO3): Two Mixed-Anion Cerium Iodates with Good Nonlinear Optical and Birefringent Properties.

Two new mixed-anion cerium iodates, namely, Ce(IO3)3F and Ce(IO3)2(NO3), have been rationally designed through the integration of hybrid anionic functional building blocks (FBBs). The structure of Ce(IO3)3F features a novel [Ce(IO3)3F] bilayer, and the material exhibits large birefringence (0.225 @546 nm). The structure of Ce(IO3)2(NO3) features [Ce3(IO3)6]3+ triple layers that are further linked by planar NO3- units. Ce(IO3)2(NO3) shows a moderate SHG response (1 × KDP) and a high laser-induced damage threshold value (22 × AgGaS2). This work demonstrates that the rich coordination geometries of cerium cations facilitate tuning of the structures of related compounds through modulating anionic FBBs.

A Laser Damage Threshold for Microscope Glass Slides

Laser-based light sources have fostered innovative developments in biomedical and biosensor fields. However, laser-induced damage to optical components is a limitation for designing and implementing highly sensitive biosensors, necessitating the development and characterization of suitable optical components. Microscope glass slides are among the most extensively used optical units in this field. This study investigated the laser-induced damage threshold (LIDT) of high-quality microscope glass slides obtained from three different vendors. An S-on-1 protocol following the ISO 21254 series standards was adopted to ensure a meaningful comparative analysis. Multiple laser pulses at a constant fluence (at the three laser wavelengths most widely used in biosensors) were used for LIDT tests. An automated test bench was developed and employed to minimize the influence of human factors on the test results. The fatigue damage mechanism was observed in all the samples. The findings revealed good consistency among LIDT values within and across batches from the same vendor. However, a notable discrepancy was observed when comparing the results of slides obtained from different vendors, with threshold values differing by up to two-fold. This study emphasizes the need to carefully consider the glass material source when selecting microscope glass slides for laser-sensitive applications.

Monolayer organic thin films as particle-contamination–resistant coatings

Three organic monolayers coatings were developed and tested for their effectiveness to increase cleaning efficiency of attached microscale particles by air flows. The experiments were performed using silica substrates coated with these organic thin films and subsequently exposed to stainless-steel and silica microparticles as a model of contamination. Laser-induced–damage tests confirmed that the coatings do not affect the laser-induced–damage threshold values. The particle exposure results suggest that although the accumulation of particles is not significantly affected under the experimental conditions used in this work, the coated substrates exhibit significantly improved cleaning efficiency with a gas flow. A size-distribution analysis was conducted to study the adsorption and cleaning efficiency of particles of different sizes. It was observed that larger size (> 5-μm) particles can be removed from coated substrates with almost 100% efficiency. It was also determined that the coatings improve the cleaning efficiency of the smaller particles (≤ 5 μm) by 17% to 30% for the stainless steel metal and 19% to 38% for the silica particles.

Significant enhancement in laser damage resistance of YAG crystal surface by plasma etching.

The high-quality surface of an optical element is a prerequisite for a high-power laser system design. Yttrium aluminum garnet (YAG) crystal is one of the most important materials for solid-state laser active medium. Laser-induced damage threshold (LIDT) of the YAG crystals might substantially limit the maximum output power of the whole laser system. In this research, we show the novel possibility of significant LIDT enhancement via plasma etching of YAG crystal surface for picosecond laser pulse durations. The dependence of the LIDT on the etching depth was investigated. With the optimized etching conditions, the LIDT value was increased by more than three times and reached the intrinsic LIDT of the bulk crystal.

Growth and characterization of L - Methionine Barium Bromide (LMBB) semi-organic crystal for optical limiting applications

The semi-organic nonlinear optical single crystal was grown from an aqueous solution by a slow evaporation solution technique (SEST) at room temperature. The characterization of the crystal was made using single crystal x-ray diffraction analysis and it was found to be L-Methionine Barium Bromide (LMBB) crystallized in a monoclinic system with space group C2/c and the cell parameter values are a= 10.74Å, b= 7.39Å, c= 8.69Å, α = γ = 90°, β = 113.53°. The UV-Vis-NIR spectroscopic study revealed that the crystal has good optical transparency and a lower cut-off wavelength was found to be 246 nm and also evaluated linear optical properties such as extinction coefficient and reflectance. The luminescence behavior of LMBB has been analyzed by fluorescence (FL) spectral study. The presence of functional groups in the LMBB is confirmed by FT-IR and FT-Raman vibrational patterns. The hardness (Hv), Meyer’s index (n), elastic stiffness constant (C11), yield strength (σy), knoop hardness (Hk), fracture toughness (Kc), and brittleness index (Bi) were analyzed using Vickers microhardness tester. Dielectric behavior as a function of frequency was examined. The laser-induced damage threshold value was found to be higher than that of KDP. The surface morphology of the as-grown crystal was determined using the SEM technique. Energy dispersive X-ray analysis was used to determine the chemical composition of the LMBB crystal. The nonlinearity coefficient (β) is measured as 1.7 × 10−11 m/W using the open aperture Z-scan technique (Nd: YAG, 532 nm, 9 ns), which results from an effective two-photon absorption phenomenon. The resulting optical limiting behavior has a fluence threshold of 8.26 × 1012 W/m2 making the LMBB a potential candidate for optical limiting devices.

High-Strength Optical Coatings for Single-Crystal ZnGeP2 by the IBS Method Using Selenide and Oxide Materials

The paper presents the results on the development of an optical coating for a single-crystal ZnGeP2 substrate based on a selenide-oxide pair of materials (ZnSe/Al2O3). The obtained coating ensures the operation of OPO in the mid-IR range up to 5 μm wavelengths. The possibility of ZnSe sputtering by the IBS method is shown. The obtained optical coating has a high laser-induced damage threshold (LIDT) value at a 2097 µm wavelength: WoE=3.51 J/cm2 in energy density and WoP= 101 W/cm2 in power density at a 10 KHz pulse repetition frequency and a pulse duration of 35 ns. Thus, it is shown for the first time that the pair of materials ZnSe/Al2O3 can be used for the deposition of optical coatings by the IBS method with high LIDT values for ZnGeP2 optical elements operating in the mid-IR range.

Phase Competition and Strong SHG Responses of the Li2MIIMIVSe4 Family: Atom Response Theory Predictions versus Experimental Results

Compounds of diamond-like (DL) structures are one of the important systems in searching for new high-performance infrared nonlinear optical (IR NLO) materials. However, the phase competition of the diverse DL allotropes and the origin of the SHG response at the atom and orbital level for these NLO materials remain an unsolved hot topic. In this work, the atom response theory (ART) combined with the hybrid density functional calculations was applied to explore the NLO properties of the Li2MIIMIVSe4 (MII = Zn, Cd, Hg; MIV = Si, Ge, Sn) family. Twenty-three new promising IR NLO compounds were predicted with a wide range of band gaps (1.79–3.62 eV), high SHG responses (∼0.7 to 2.5 × AGS), moderate birefringences (∼0.04), and possibly high LIDT (laser-induced damage threshold) values. Among them, Li2HgGeSe4 and Li2HgSnSe4 with the Pna21 structure were experimentally confirmed very recently. The phase competition and the order of band gaps of these compounds were explained from the viewpoint of the crystal structure and chemical bonding. Our ART analyses showed that the large NLO coefficients of these selenides arise mainly from the Se-4p orbitals (∼76%) while the anomaly low contribution of Hg is attributed to the tiny d–p covalent interactions. The SHG responses of all structures were rationalized by the deffp vs αsum/(NEg) linear relationship, showing the importance of this relation in designing and synthesizing new NLO materials.

Study on laser-induced damage of TbBiIG crystal at 1064 nm.

With the development of miniaturization of high-energy laser systems, a new Faraday rotator material must be studied to realize the miniaturization and integration of optical isolators. In this paper, high-quality (TbBi)3Fe5O12 (TbBiIG) and Ca-doped (TbBi)3Fe5O12 (Ca: TbBiIG) single crystal films with hundreds of microns thickness were grown by liquid phase epitaxy method on (111) oriented garnet substrate. The crystal structure, magneto-optical (MO), optical and laser induced damage properties were investigated in detail. We found that the (TbBi)3Fe5O12 film has outstanding magneto-optical and laser-induced damage properties. Optical and MO properties indicate that TbBiIG films have a high specific faraday rotation angle of 1452 deg/cm at 1310 nm, and 2812 deg/cm at 1064 nm, absorption coefficient (α) is 5.63 cm-1 and 15.7 cm-1 at 1310 nm and 1064 nm, respectively. The laser-induced damage threshold (LIDT) of TbBiIG irradiated by a multi-frequency laser is 8.91 J/cm2. The light absorption has a significant impact on LIDT value. Rare-earth ion doped iron garnet (RIG) material is a very potential MO material, which can greatly reduce the size and weight of optical isolators in the 1064 nm band.

Homovalent cation substitutions leading to new lithium-containing La3CuSiS7 family members having chiral, uniaxial structures and exhibiting second- and third-harmonic generation

Eighteen isotypic, lithium-containing rare-earth sulfides, crystallizing in the chiral, polar, and noncentrosymmetric space group P63 with the La3CuSiS7-structure type have been prepared via direct combination of the elements or binary sulfides; nine of these compounds are reported for the first time. The structures of these compounds, with the formulae Ln3LiTS7 (Ln = La, Ce, Pr, Nd, Sm, Gd, and Dy for T = Si or Ge; Ln = La, Ce, Pr, and Nd for T = Sn), were determined by single crystal X-ray diffraction. According to X-ray powder diffraction data, the Ln3LiTS7 compounds are the major phase of the reaction products. All of the compounds are semiconductors with optical bandgaps spanning nearly the entire visible region. The Si- and Ge-containing analogs show high thermal stability,> 1000 °C, while the Sn-containing compounds melt in the vicinity of ~740 °C. The compounds show potentially broad regions of optical transparency in the infrared regime. Calculated bond valence sums (BVSs) and global instability index (G) values confirm the Ln3+ oxidation state and stable crystal structures with reasonable strain, respectively. Ce3LiGeS7 and Ce3LiSnS7 display non-phase-matching but significant second-harmonic generation responses with χ2 values of 21 ± 1 and 28 ± 1 pm/V, respectively at λ = 1.8 µm. The laser-induced damage threshold values for Ce3LiGeS7 and Ce3LiSnS7 are> 3 × commercial AgGaSe2, for picosecond pulses at λ = 1.064 µm. These two compounds also exhibit moderate third-harmonic generation responses. Additionally, crystal-chemical correlations are discussed.

AMoO3(IO3) (A = Na and K): Two promising optical materials via properly assembling the Λ-shaped basic building units

Herein, we reported two alkali metal molybdenum(VI) iodates, namely, NaMoO3(IO3) and γ-KMoO3(IO3) with 1D and 3D [MoO3(IO3)]− anionic architectures, respectively. The novel 1D chain in NaMoO3(IO3) and the 3D network in γ-KMoO3(IO3) are constructed by the 0D Λ-shaped cis-[MoO4(IO3)2]4− building units interconnected by bridging IO3− anions as well as the corner-sharing of oxo anions. Importantly, the polar γ-KMoO3(IO3) exhibits a very large second-harmonic generation (SHG) effect of 12 × KH2PO4 (KDP) under 1064 nm laser radiation, a high laser-Induced damage threshold value (52 × AgGaS2), and a moderate birefringence of 0.087@1064 nm, whereas the centrosymmetric NaMoO3(IO3) has a large birefringence of 0.208@1064 nm. This study further proves the useful route of exploring promising optical materials via assembling the 0D basic building units into higher dimensional anionic architectures.

Helical {[HgS]}n Chain-Induced Balanced Nonlinear-Optical Performance for Trigonal Mercury Sulfide.

Large second-harmonic-generation (SHG) response and enhanced laser-induced damage threshold (LIDT) compared with benchmark AgGaS2 (AGS), together with a simple chemical composition and exclusion of the light-sensitive Ag element, are vital for exploration of superior IR nonlinear-optical (NLO) materials beyond AGS. Herein, we report trigonal HgS as a highly promising IR NLO material. It was obtained by a facile one-pot hydrothermal reaction, and its noncentrosymmetric P3221 structure features a unique dumbbell-shaped HgS2 group and a neutral helical {[HgS]}n chain, which first served as a SHG functional motif. Its polycrystalline powder sample exhibits a phase-matchable SHG response comparable to that of AGS and a LIDT value of 1.2 × AGS. Structural analysis and theoretical calculation suggest that the {[HgS]}n chain plays an important role for excellent NLO performance. This work not only provides a strong candidate for IR NLO application but also introduces a new SHG functional motif for the design of future NLO materials.

Properties of Hafnium and Aluminium Silicates Coatings Obtained by PLD

We report on the deposition and characterization of hafnium silicate and aluminium silicate thin films for different applications in optics and electronics. Pulsed laser deposition in a controllable oxygen atmosphere was used as a processing technique, with optimized parameters in terms of laser wavelength, laser fluence and oxygen pressure. The thin films were investigated using atomic force microscopy, spectroscopic ellipsometry, UV–VIS spectroscopy and X-ray photoelectron spectroscopy. The morphological investigations evidenced uniform layers with low roughness (in the order of nanometres). The optical investigations revealed that aluminium silicate layers with low roughness and low absorption in the infrared (IR) range can be obtained at high substrate temperatures (600 °C). The behaviour of the silicate thin films with respect to the nanosecond IR laser irradiation revealed that aluminium silicate layers have higher laser-induced damage threshold values in comparison with hafnium silicate.

Impact of threshold assessment methods in laser-induced damage measurements using the examples of CCD, CMOS, and DMD.

Based on our earlier investigations, we continued and intensified our effort on the assessment of laser-induced damage effects in the visible range on a digital micromirror device (DMD) in comparison to different electro-optical imaging sensors such as complementary metal-oxide-semiconductors (CMOS) and charge-coupled devices (CCD). The main two objectives of our current work are: i) to fill the gap for the damage threshold regarding the time scale of picosecond pulses (527 nm) for CCD and CMOS devices and ii) evaluate the performance of a new device, the DMD, with both nanosecond pulses (532 nm) and picosecond pulses (527 nm) and compare the results with those of the CCD/CMOS. In the course of this research, we improved the experimental setup. Furthermore, we characterized the damage caused by laser pulse energies exceeding the laser-induced damage threshold (LIDT). For both the CMOS and CCD cameras, we received damage thresholds of about 10mJ/cm2 (picosecond pulses). For the DMD, we obtained LIDT values of 130mJ/cm2 (nanosecond laser pulses) and 1500mJ/cm2 (picosecond laser pulses). In case of the CMOS devices, we additionally compared the appearance of the damage obtained from the output signal of the camera under test and the microscope images of the surface of the camera. The first visible changes on the surface of the sensor occurred at energy densities that are an order of magnitude higher than the threshold values related to the output signal.

Three-in-One Strategy Constructing a Series of Hybrid Tetrahedral Motif-Based Selenides with Balanced Second-Order Nonlinear Optical Performance.

Concurrently achieving suitable second harmonic generation (SHG) effect and high laser-induced damage threshold (LIDT) is challenging for infrared nonlinear optical (NLO) materials. Here, a series of pentanary infrared NLO materials CsMIIIMIVSnSe6 (MIII = Ga, In; MIV = Si, Ge) have been obtained by a three-in-one strategy, viz. three kinds of elements (MIII, MIV, and Sn) in one position, which is first adopted to design NLO materials. Their three-dimensional structures are constructed by the MQ4 (M denotes MIII, MIV, and Sn) tetrahedral units. They exhibit promising hybrid NLO properties, witnessed by their moderate/large SHG effects of 0.52, 0.98, 1.05, and 1.12 × AgGaS2, and high powder LIDT values of 6.9, 4.1, 8.1, and 5.4 × AgGaS2, respectively. These NLO properties are well verified by the DFT calculation results. The three-in-one strategy of designing high-performance infrared NLO materials will stimulate more investigations in this field.

Crystallization behavior of ion beam sputtered HfO2 thin films and its effect on the laser-induced damage threshold

In this work, we present our results about the thermal crystallization of ion beam sputtered hafnia on 0001 SiO2 substrates and its effect on the laser-induced damage threshold (LIDT). The crystallization process was studied using in-situ X-ray diffractometry. We determined an activation energy for crystallization of 2.6 ± 0.5 eV. It was found that the growth of the crystallites follows a two-dimensional growth mode. This, in combination with the high activation energy, leads to an apparent layer thickness-dependent crystallization temperature. LIDT measurements @355 nm on thermally treated 3 quarter-wave thick hafnia layers show a decrement of the 0% LIDT for 1 h @773 K treatment. Thermal treatment for 5 h leads to a significant increment of the LIDT values.

Investigation on the optical, spectral, electrical, mechanical, and laser damage threshold studies of bis (4-acetylanilinium) tetrachloridozincate (B4ATCZ) crystal

An efficient semi-organic nonlinear optical bis (4-acetylanilinium) tetrachloridozincate [(C8H10NO)2 ZnCl4] (B4ATCZ) single crystal was synthesized and successfully grown by the slow evaporation method. The single-crystal X-ray diffraction data confirm that B4ATCZ crystallized into an orthorhombic crystal system (Cmca). The UV–Vis–NIR transmittance spectrum was taken to assess the optical transmission, cut-off wavelength, and bandgap energy. The TG–DSC investigation ensures that the B4ATCZ is stable up to 235 °C. The mechanical behavior of the B4ATCZ compound was determined by Vickers Microhardness analysis. The surface laser-induced damage threshold value of the grown B4ATCZ crystal was endowed to be 19.78 GW/cm2 on testing with 1064 nm Nd: YAG laser radiation. The positive photoconductive properties and charge transport mechanism of B4ATCZ crystal were analyzed through photoconductivity and dielectric studies. The electron excitation and lifetime measurements of the molecules in the B4ATCZ crystal were studied by fluorescence spectral analysis. The HOMO–LUMO analysis evidently interprets the occurrence of N–H⋯O and N–H⋯Cl intermolecular hydrogen bonds influencing the charge transfer in the system. The electrostatic potential surface reveals the possible sites for hydrogen bonding electrophilic and nucleophilic interactions. Third-order nonlinear optical activity evaluated by the Z-scan measurements indicates the self-focusing and reverse saturable absorption in the crystal. The aforesaid results affirm that the metal-organic B4ATCZ is a potential material for optoelectronic and nonlinear optical device applications.

Correlation between Photoluminescence Properties of Surface Defects and Laser-Induced Damage Threshold of Fused Silica

Laser-induced damage threshold is the main limitation for fused silica optics in high-power laser applications. The existence of various defects near the surface is the key factor for the degradation of the threshold. In this work, the photoluminescence spectra at different regions of the damaged and recovered fused silica samples are recorded to analyze the correlation between photoluminescence of surface defects and laser-induced damage threshold. The experimental data concluded the inverse proportional correlation between fluorescence and laser-induced damage threshold value. The weak photoluminescence is the guarantee of the high laser-induced damage threshold, and then the higher local Si nanocluster concentration corresponds with the higher laser-induced damage threshold value for the fused silica optics after CO2 laser treatment. The investigation reveals that photoluminescence measurement can be employed to check the quality of pristine fused silica and evaluate the tendency of the laser-induced damage threshold value. The current results are helpful for understanding the evolution of interaction from CO2 laser treatment and fused silica optics and can provide the guide of process technology for the high quality of fused silica optics.