High Damage Threshold Research Articles

Double alkaline earth metals sulfide SrMgGeS4 with high laser-induced damage threshold and strong second-harmonic generation

The exploration of anti-laser damage wide band gap infrared (IR) nonlinear optical (NLO) materials is urgently needed but challenging due to the contradiction between wide band gap and large NLO coefficient. Herein, by introducing [MQ4] (Q = S, Se) tetrahedral units into the AIIBIICIVD4VI family, three double alkaline earth metals chalcogenides SrMgGeS4, BaMgSiSe4 and SrMgSiSe4 with unprecedented [MgGeS6] or [MgSiSe6] dimers are rationally designed and fabricated. The compounds display an interesting structural change from centrosymmetric (CS) I41/acd (BaMgSiSe4, the first CS compound in this family) to non-centrosymmetric Ama2 (SrMgSiSe4) and Fdd2 (SrMgGeS4). Importantly, SrMgGeS4 shows a wide band gap (3.58 eV), a high laser-induced damage threshold (∼6 × AGS), a moderate birefringence (∼0.11@1064 nm), and a strong second-harmonic generation (SHG) response (∼1.1 × AGS), achieving a good balance between wide band gap (Eg ≥ 3.5 eV) and large SHG response (≥1.0 × AGS) for an excellent IR NLO material. The results enrich the chemical and structural diversity of chalcogenides and give insights into the design of high-performance IR NLO materials.

2.2 kW single-mode narrow-linewidth laser delivery through a hollow-core fiber

Antiresonant hollow-core fibers (AR-HCFs) have opened up exciting possibilities for high-energy and high-power laser delivery because of their exceptionally low nonlinearities and high damage thresholds. While these fiber designs offer great potential for handling kilowatt-class powers, it is crucial to investigate their performance at multi-kW power levels. Until now, transmission of narrow-linewidth single-mode lasers at multi-kW power levels through a HCF has not been demonstrated, to our knowledge. Here, we present the delivery of a record 2.2 kW laser power with an input spectral linewidth of 86 GHz, centered at 1080 nm, while maintaining 95% transmission efficiency and beam quality (M2) of 1.03. This was achieved via a 104.5 m single-mode five-tube nested AR-HCF with 0.79 dB/km loss. Furthermore, we show power delivery of 1.7 kW with a spectral linewidth as narrow as 38 GHz through the same fiber. Our results could lead to a new generation of fiber-based laser beam delivery systems with applications in precision machining, nonlinear science, directed energy, and power beaming over fiber.

Ca2 Ln(BS3 )(SiS4 ) (Ln = La, Ce, and Gd): Mixed Metal Thioborate-Thiosilicates as Well-Performed Infrared Nonlinear Optical Materials.

The first examples of thioborate-thiosilicates, namely Ca2 Ln(BS3 )(SiS4 ) (Ln = La, Ce, and Gd), are synthesized by rationally designed high-temperature solid-state reactions. They crystalize in the polar space group P63 mc and feature a novel three-dimensionalcrystal structure in which the discrete [BS3 ]3- and [SiS4 ]4- anionic groups are linked by Ca2+ and Ln3+ cations occupying the same atomic site. Remarkably, all three compounds show comprehensive properties required as promising infrared nonlinear optical materials, including phase-matchable strong second harmonic generation (SHG) responses at 2.05µm (1.1-1.2 times that of AgGaS2 ), high laser-induced damage thresholds (7-10 times that of AgGaS2 ), wide light transmission range (0.45-11µm), high thermal stabilities (>800 °C), and large calculated birefringence (0.126-0.149 @1064nm), which justify the material design strategy of combining [BS3 ]3- and [SiS4 ]4- active units. Theoretical calculations suggest that their large SHG effects originate mainly from the synergy effects of the LnS6 , BS3 , and SiS4 groups. This work not only broadens the scope of research on metal chalcogenides but also provides a new synthetic route for mixed anionic thioborates.

The compatibly large nonlinear optical effect and high laser-induced damage threshold in a thiophosphate CsInP2S7 constructed with [P2S7]4- and [InS6]9-

It is challenging to cooperatively improve the nonlinear optical (NLO) efficiency and the laser-induced damage threshold (LIDT). This work reports a novel IR NLO materials CsInP2S7 (CIPS) designed by combination the strategies of alkali metals substitution and microscopic NLO units PS4 introduction based on AgGaS2. CIPS was composed of strongly distorted [InS6]9- octahedra and [P2S7]4- dimers constructed by corner-sharing [PS4]3-, which increase the NLO efficiency and decrease thermal expansion anisotropy simultaneously. Compared with AgGaS2, CIPS exhibited strong phase matchable NLO response ca. 1.1 × AGS@2.1 µm, high LIDT ca. 20.8 × AgGaS2, and IR transparency up to 15.3 µm. Structural analysis and theoretical investigation confirmed that large SHG effect and ultrahigh LIDT of CIPS originated from the synergistic contribution of [InS6]9- octahedra and [P2S7]4- dimers. These results indicate that CIPS is a promising NLO candidate in the mid-IR region, and this study provides a new approach for developing potential NLO-LIDT compatible materials.

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.

Chiral Hybrid Germanium(II) Halide with Strong Nonlinear Chiroptical Properties.

Due to the pronounced anisotropic response to circularly polarized light, chiral hybrid organic-inorganic metal halides have been regarded as promising candidates for the application in nonlinear chiroptics, especially for the second-harmonic generation circular dichroism (SHG-CD) effect. However, designing novel lead-free chiral hybrid metal halides with large anisotropy factors and high laser-induced damage thresholds (LDT) of SHG-CD remains challenging. Herein, we develop the first chiral hybrid germanium halide, (R/S-NEA)3 Ge2 I7 ⋅H2 O (R/S-NGI), and systematically investigated its linear and nonlinear chiroptical properties. S-NGI and R-NGI exhibit large anisotropy factors (gSHG-CD ) of 0.45 and 0.48, respectively, along with a high LDT of 38.46 GW/cm2 ; these anisotropy factors were the highest values among the reported lead-free chiral hybrid metal halides. Moreover, the effective second-order nonlinear optical coefficient of S-NGI could reach up to 0.86 pm/V, which was 2.9 times higher than that of commercial Y-cut quartz. Our findings facilitate a new avenue toward lead-free chiral hybrid metal halides, and their implementation in nonlinear chiroptical applications.

Impact of the multilayer dielectric design on the laser-induced damage threshold of pulse compression gratings for petawatt-class lasers.

The peak-power of petawatt-class lasers is limited by laser-induced damage to final optical components, especially on the pulse compression gratings. Multilayer dielectric (MLD) gratings are widely used in compressor systems because they exhibit a high diffraction efficiency and high damage threshold. It is now well established that the etching profile plays a key role in the electric field distribution, which influences the laser damage resistance of MLD gratings. However, less attention has been devoted to the influence of the multilayer design on the laser damage resistance of MLD gratings. In this Letter, we numerically and experimentally evidence the impact of the dielectric stack design on the electric field intensity (EFI) and the laser-induced damage threshold (LIDT). Three different MLD gratings are designed and manufactured to perform laser damage tests. On the basis of the expected EFIs and diffraction efficiencies, the measured LIDTs show how the multilayer design influences the laser resistance of the MLD gratings. This result highlights the impact of the multilayer dielectric design on the electric field distribution and shows how to further improve the laser-induced damage threshold of pulse compression gratings.

Laser damage properties of LiB3O5 crystal surface under UV laser irradiation.

LiB3O5 (LBO) crystal has a very high bulk laser damage threshold. Laser damage often occurs on the surfaces with a large number of processing defects during application. In this paper, the surface laser damage threshold, damage growth threshold, and damage growth curve of LBO crystal and fused silica under the same processing process have been comparatively studied by using a 355 nm pulsed laser. The surface laser damage performance of LBO crystal has been comprehensive evaluated. The results show that the laser damage threshold and damage growth threshold of LBO are about twice that of fused silica, and the damage growth coefficient is about 0.7 times that of fused silica. The detection and analysis of impurity defects and photothermal weak absorption defects show that the subsurface defects of LBO crystal are less than that of fused silica. Laser damage morphologies show that the damage process is related to strongly bonded chemical structure and anisotropic physical characteristics of LBO crystal. These characteristics together determine the high threshold damage performance of LBO crystal. The results of this study are of great guidance for the application of LBO crystal in high-power laser systems.

Passively Q-Switched Thulium-Holmium Doped Fibre Laser with Electrochemical Exfoliation Graphene in Chitin Based Passive Saturable Absorber

Recent years saw low-dimensional carbon nanostructures like graphene as excellent saturable absorber (SA) for its unique electric and optical properties. Graphene exhibits ultrafast recovery times and high damage thresholds and can be manufactured by relatively simple methods. In this work, Graphene was synthesized using the electrochemical exfoliation (ECE) method. Chitin biopolymer was used to develop graphene-based SA as a more environmentally friendly alternative to conventional synthetic polymers. The fabricated passive SA was then integrated into Thulium-Holmium-doped fibre laser (THDFL) in ring cavity for pulsed laser generation via Q-switching. The optical and physical properties of the graphene-based SA were characterized using Raman spectroscopy, field emission scanning electron microscopy (FESEM) and energy-dispersive x-ray spectroscopy (EDS). Q-switched pulse was successfully demonstrated using the fabricated graphene SAs. ECE graphene-chitin SA generated a Q-switched pulse region at 2 micro-metre with the repetition rate and shortest pulse width of 67.78 kHZ and 10.03 micro-second, respectively. The signal-to-noise ratio (SNR) values obtained was 40 dB indicating high stability of the pulse laser-generated. This study demonstrated the potential of graphene embedded in chitin biopolymer as a sustainable and environmentally friendly SA for a wide range of applications, particularly for pulsed fibre lasers.

α- and β-(C4H5N2O)(IO3)·HIO3: Two SHG Materials Based on Organic-Inorganic Hybrid Iodates.

Organic-inorganic hybrid nonlinear optical (NLO) materials are highly anticipated because of the integration of both merits of the organic and inorganic moieties. Herein, the 2-pyrimidinone cation (C4H5N2O)+ has been incorporated into the iodate system to form two polymorphic organic-inorganic hybrid iodates, namely, α- and β-(C4H5N2O)(IO3)·HIO3. They crystallize in different polar space groups (Ia and Pca21), and their structures feature one-dimensional (1D) chain structures composed of (C4H5N2O)+ cations, IO3- anions, and HIO3 molecules interconnected via hydrogen bonds. α- and β-(C4H5N2O) (IO3)·HIO3 exhibit strong and moderate second-harmonic-generation (SHG) responses of 6.4 and 0.9 × KH2PO4 (KDP), respectively, the same band gaps of 3.65 eV, and high powder laser-induced damage threshold (LIDT) values [51 and 57 × AgGaS2 (AGS)]. The results of theoretical calculations revealed that the large SHG effect of α-(C4H5N2O)(IO3)·HIO3 originated from the IO3 and HIO3 groups. This work indicates that (C4H5N2O)+ is a potential group for designing new NLO materials with brilliant optical performances.

KHg4Ga3S9: A Hg-Based Sulfide with Nonlinear-Optical Activity in the A-MII-MIII-Q (A = Alkali Metal; MII = d10 Metal; MIII = Ga, In; Q = S, Se) System.

The search for new high-performance infrared (IR) nonlinear-optical (NLO) materials is a hot topic in the fields of laser chemistry and inorganic solid-state chemistry. Here, a new Hg-based sulfide KHg4Ga3S9 in the family of A-MII-MIII-Q (A = alkali metal; MII = d10 metal; MIII = Ga, In; Q = S, Se) was synthesized. It crystallizes in the orthogonal system of the C2221 structure, which is rare for IR NLO chalcogenides. Its anionic framework {[Hg4Ga3S9]-}∞ is constructed by two types of interconnected helical chains, viz., the inner layer ({[Hg6Ga2S29/3]4/3-}∞) and the outer layer ({[Hg2Ga4S25/3]2/3-}∞). It exhibits a moderate NLO response and a high laser-induced damage threshold. Theoretical calculations indicate that the HgS4 unit accounts for its much larger NLO response compared to RbCd4Ga3S9. The influence of alkali metals and d10 metals on the initial phase-matching wavelength is also discussed. This work provides inspiration for improving the properties of NLO materials' properties.

High average power ultrafast laser technologies for driving future advanced accelerators

Large scale laser facilities are needed to advance the energy frontier in high energy physics and accelerator physics. Laser plasma accelerators are core to advanced accelerator concepts aimed at reaching TeV electron electron colliders. In these facilities, intense laser pulses drive plasmas and are used to accelerate electrons to high energies in remarkably short distances. A laser plasma accelerator could in principle reach high energies with an accelerating length that is 1000 times shorter than in conventional RF based accelerators. Notionally, laser driven particle beam energies could scale beyond state of the art conventional accelerators. LPAs have produced multi GeV electron beams in about 20 cm with relative energy spread of about 2 percent, supported by highly developed laser technology. This validates key elements of the US DOE strategy for such accelerators to enable future colliders but extending best results to date to a TeV collider will require lasers with higher average power. While the per pulse energies envisioned for laser driven colliders are achievable with current lasers, low laser repetition rates limit potential collider luminosity. Applications will require rates of kHz to tens of kHz at Joules of energy and high efficiency, and a collider would require about 100 such stages, a leap from current Hz class LPAs. This represents a challenging 1000 fold increase in laser repetition rates beyond current state of the art. This whitepaper describes current research and outlook for candidate laser systems as well as the accompanying broadband and high damage threshold optics needed for driving future advanced accelerators.

High-performance passively Q-switched fiber laser based on CuFeO2/SiO2 as saturable absorber

In this paper, we report the optical properties and applications of the CuFeO2 (CFO)/SiO2 novel saturable absorber (SA) by the sol–gel method. The measured results show that our SA’s modulation depth, unsaturated loss and damage threshold are 10.9%, 10.1% and 5121 mJ/cm 2, respectively. High-quality passively Q-switched fiber laser output at 1.5μm was successfully achieved using CFO/SiO2 SA. Due to the high damage threshold and low insertion loss of the SA, the maximum output power of the laser are 59.6 mW, the optical conversion efficiency is 6.4%, much higher than other reports, corresponding to an output pulse’ peak power and single pulse energy of up to 723.98 mW and 307.7 nJ, and the signal-to-noise ratio of 74 dB indicating its stability. The results indicate that the CFO/SiO2 SA prepared by the sol–gel method provides a new opportunity to develop high-performance SA and high-power passive Q-switched fiber lasers.

High-damage-threshold mid-infrared saturable absorber enabled by tantalum carbide nanoparticles.

A stable mid-infrared saturable absorber with a high damage threshold is urgently required for high-performance optical modulation in the mid-infrared regime. Here, we demonstrate stable mid-infrared erbium-doped fiber laser generation modulated by tantalum carbide nanoparticles (TaC NPs) experimentally. The TaC NPs show high physicochemical stability, obvious nonlinear optical absorption, and a high damage threshold. By introducing the TaC-based saturable absorber into an erbium-doped fiber laser, stable nanosecond pulses can be successfully delivered with a minimum pulse duration of 575 ns and signal-to-noise ratio of over 40 dB. The experimental results show that TaC NPs can act as a stable mid-infrared pulse modulator, and may make inroads for developing highly stable broadband optoelectronic devices.

Harmonic Mode‐Locked Er‐Doped Fiber Laser Based on a Microfiber‐Based PbS Nanoparticle Saturable Absorber

AbstractLead sulfide (PbS) is a nanomaterial with excellent optical and chemical properties, such as a narrow bandgap (0.37 eV), high thermal damage threshold, and high stability. Obviously, it is appropriate as a saturable absorber (SA) device for ultrafast photonics. However, PbS nanoparticles (NPs) as the SA of ultrashort harmonic mode‐locked pulse still haven't been demonstrated at present. In this paper, the PbS NPs are made into an SA‐device‐based microfiber by optical deposition method and connected in an integrated Erbium‐doped fiber laser. And both characteristics and nonlinear optical properties of PbS NPs have been systemically investigated. A fundamental frequency mode‐locked pulsed laser is proposed, whose central wavelength is 1560 nm, and the pulse width is 1 ps. In addition, high repetition rate operations are achieved, with a maximum repetition rate of 833 MHz. This is the first time that PbS NPs are used to generate 96th‐order harmonic mode‐locking, and the corresponding pulse duration is 987 fs. It is demonstrated that PbS NPs are a kind of SA photonic material with excellent performance. It can improve the communication capacity by applying fiber communication, and it has potential application value even in material processing and optical comb.

Cs4 Zn5 P6 S18 I2 : the Largest Birefringence in Chalcohalide Achieved by Highly Polarizable Nonlinear Optical Functional Motifs.

Chalcohalides not only keep the balance between the nonlinear optical (NLO) coefficient and wide band gap, but also provide a promising solution to achieve sufficient birefringence for phase-matching ability in NLO crystals. In this study, a novel chalcohalide, Cs4 Zn5 P6 S18 I2 (1) is successfully synthesized, by incorporating the highly electropositive Cs and the large electronegative I element into the zinc thiophosphate. Its 3D open framework features an edge-shared by distorted [ZnS4 ], ethanol-like [P2 S6 ], and unusual [ZnS2 I2 ] polyhedrons, which is inconsistent with the soft-hard-acids-bases theory. Remarkably, compound 1 simultaneously exhibits the large second-harmonic generation (SHG, 1.1×AgGaS2 , @1.3µm) and a wide band gap (3.75eV) toward a high laser-induced damage threshold (16.7×AgGaS2 , @1.06µm), satisfying the rigorous requirements for a prominent infrared NLO material with concurrent SHG intensity (≥0.5×AGS) and band gap (≥3.5eV). Moreover, to the best of the knowledge, the experimental result shows that phase 1 has the largest birefringence (0.108, @546nm) in chalcohalide and meets phase-matching behavior demand originating from the polarizable anisotropy of NLO-functional motifs. This finding may provide great opportunities for designing birefringent chalcohalides.

MgSiP2: An Infrared Nonlinear Optical Crystal with a Large Non‐Resonant Phase‐Matchable Second Harmonic Coefficient and High Laser Damage Threshold

AbstractSuperior infrared nonlinear optical (NLO) crystals are in urgent demand in the development of lasers and optical technologies for communications and computing. The critical challenge is to find a crystal with large non‐resonant phase‐matchable NLO coefficients and high laser damage threshold (LDTs) simultaneously, which however scale inversely. This work reports such a material, MgSiP2, that exhibits a large second harmonic generation (SHG) coefficient of d14≈d36 = 89 ± 5 pm V−1 at 1550 nm fundamental wavelength, surpassing the commercial NLO crystals AgGaS2, AgGaSe2, and ZnGeP2. First principles theory reveals the polarizability and geometric arrangement of the [SiP4] tetrahedral units as the origin of this large nonlinear response. Remarkably, it also exhibits a high LDT value of 684 GW cm−2, which is six times larger than ZnGeP2 and three times larger than CdSiP2. It has a wide transparency window of 0.53–10.35 µm, allowing broadband tunability. Further, it is Type I and Type II phase‐matchable with large effective SHG coefficients of deff,I ≈80.2 pm V−1 and deff,II ≈73.4 pm V−1. The outstanding properties of MgSiP2 make it a highly attractive candidate for optical frequency conversion in the infrared.

Development of 2 μm all‐solid‐state pulsed laser using a saturable absorber

AbstractThe pulse laser using a saturable absorber as a passive device has the advantages of narrow pulse width, high repetition rate, and high pulse energy. Low‐dimensional materials have attracted research interest in recent years due to their excellent saturable absorption properties, ultra‐fast carrier response speed, high damage threshold, and so on. This paper gives a brief review of the state‐of‐the‐at 2 µm solid‐state lasers using saturable absorbers. The output performance of lasers in repetition rate, pulse energy, pulse width, and wavelength are summarized. The paper is expected to provide a development direction of novel materials as saturable absorbers in 2 µm solid‐state lasers.

Ultra-broad bandwidth low-dispersion mirror with smooth dispersion and high laser damage resistance.

Low-dispersion mirrors (LDMs), which require a broad bandwidth, low dispersion, and high damage threshold, are essential optics in ultra-intense and ultra-short laser devices. Bragg mirrors and chirped LDMs do not satisfy these requirements simultaneously. We propose a novel LDM (NLDM) based on the hump-like structure and quarter wavelength optical thickness (QWOT) structure to achieve a broad bandwidth, smooth dispersion, and high robustness. The spectral and dispersion characteristics of the two structures compensate for each other, which makes up for the deficiency that the dispersion bandwidth of the sinusoidal modulation structure cannot be broadened. Based on this structure, the LDM can achieve a design bandwidth of 240 nm and support the transmission of sub-11-fs pulses. The accuracy of the NLDM is experimentally evaluated. The structure shows the potential for broad-spectrum laser damage performance due to the low electric field intensity. The NLDM improves the mirror performance and paves the way for a new generation of ultra-intense and ultra-short laser devices.

Synthesis, Structure, and optical properties of Y3GaGe0.5S7: A new member in the polar R3MTQ7 family

A new quaternary chalcogenide Y3GaGe0.5S7 belongs to R3MTQ7 family was discovered for the first time, which was obtained through a conventional solid-state reaction at high temperature. The crystal structure indicates that Y3GaGe0.5S7 crystallizes in hexagonal system P63 space group (a =9.6204(6) Å, c =6.0111(7) Å, V=481.80(8) Å3 and Z = 1). The crystal structure of the title compound is assembled by chains of face-sharing GaS6 octahedra that are surrounded by both discrete Y cations and isolated Ga/GeS4 tetrahedra. UV–vis–NIR spectroscopy measurement reveals that the optical band of the title compound is 2.30 eV. It shows weak Second Harmonic Generation (SHG) property but with the high laser-induce damage threshold (LIDT) value (8.55 MW/cm2), which is close to 3 times that of AgGaS2 (2.82 MW/cm2). Furthermore, the first-principle calculations are applied to depth analysis the relationship between linear and nonlinear of optical properties and crystal structure.