Optical Damage Threshold Research Articles

Photoinduced Reversible Local Deformation of the Surface Relief in Bulk Single Crystals of TlInSe2, TlGaTe2, and TlSe

Giant macroscopic expansion of the surface relief, localized within a laser spot size, has been observed in bulk single crystals of TlInSe2, TlGaTe2, and TlSe at room temperature and laser radiation densities lower by at least two orders of magnitude than the material optical damage threshold. Quantitative estimations of the deformation magnitude in this local region were obtained using an interference dilatometer. The photon absorption length was determined with the aid of spectroscopic ellipsometry. It is established that the surface deformation amounts to 2.6 × 10–3 at a laser radiation intensity of 19 mW/mm2. The observed phenomenon has a thermal nature and is probably related to a low thermal conductivity of the materials studied.

Studies on linear and nonlinear optical properties of 4-N,N-dimethylamino-4′-N′-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate crystal

4-N,N-dimethylamino-4′-N′-methyl-stilbazolium 2,4,6-trimethylbenzenesulfonate (DSTMS) terahertz organic material has been synthesized by the knoevenagel condensation method. DSTMS single crystals were grown in methanol by slow-cooling method. The linear optical property of DSTMS crystal has been studied using UV–Vis-NIR spectroscopy in the wavelength range 190–1100 nm and optical constants are calculated theoretically. The magnitude of nonlinear refractive index (10−10 m2/W), nonlinear absorption (10−3 m/W) and third order nonlinear susceptibility (10−4 esu) has been studied using Z-scan technique. Dielectric property of DSTMS crystal has been studied at frequency range 50 Hz–5 MHz. The electronic properties such as valence electron plasma energy, penn gap, fermi energy, electronic polarization, electric susceptibility of the grown crystal has been studied. Photoluminescence spectrum was recorded using xenon lamp in the range of 450–700 nm. Laser optical damage threshold of DSTMS crystal was calculated (3.57 GW/cm2) using pulsed Nd-YAG laser (1064 nm) of repetition rate 10 ns. The refractive index of the crystal (1.571) has been measured using Abbe’s Refractometer. The optical limiting behaviour of DSTMS crystal has been studied using Nd-YAG laser. The response time (τ) of optical limiting power for the crystals is 10−11 s.

WS2-Clad Microfiber Saturable Absorber for High-Energy Rectangular Pulse Fiber Laser

Tungsten disulfide (WS2), which possesses broadband nonlinear saturable absorption property, displays promising applications in passively mode-locked lasers. Recent research works have demonstrated that WS2 shows much higher thermal conductivity than other transition metal dichalcogenides, which can withstand higher optical intensity and exhibit a higher damage threshold. However, the WS2-based high-energy fiber lasers have not been extensively studied. Here, a WS2-clad microfiber (WCM) saturable absorber (SA) is exploited by an effective transferring approach, which is precisely accomplished under optical microscope. The evanescent field interaction scheme has ability to further raise the optical damage threshold, as well as take full advantage of the nonlinear effect of WS2. Based on the WCM SA, high-energy rectangular pulses are achieved in an Er-doped fiber laser whose pulse duration and energy almost increase linearly with the enhancement of pump power. The maximum energy of single pulse in the cavity can reach 810 nJ under pump power of 800 mW. The experimental results open up venues to create new high-energy laser systems with rich functionalities and novel physical effects.

Lifetime laser damage performance of β-Ga2O3 for high power applications

Gallium oxide (Ga2O3) is an emerging wide bandgap semiconductor with potential applications in power electronics and high power optical systems where gallium nitride and silicon carbide have already demonstrated unique advantages compared to gallium arsenide and silicon-based devices. Establishing the stability and breakdown conditions of these next-generation materials is critical to assessing their potential performance in devices subjected to large electric fields. Here, using systematic laser damage performance tests, we establish that β-Ga2O3 has the highest lifetime optical damage performance of any conductive material measured to date, above 10 J/cm2 (1.4 GW/cm2). This has direct implications for its use as an active component in high power laser systems and may give insight into its utility for high-power switching applications. Both heteroepitaxial and bulk β-Ga2O3 samples were benchmarked against a heteroepitaxial gallium nitride sample, revealing an order of magnitude higher optical lifetime damage threshold for β-Ga2O3. Photoluminescence and Raman spectroscopy results suggest that the exceptional damage performance of β-Ga2O3 is due to lower absorptive defect concentrations and reduced epitaxial stress.

Enhanced Ultrafast Nonlinear Optical Response in Ferrite Core/Shell Nanostructures with Excellent Optical Limiting Performance.

Nonlinear optical nanostructured materials are gaining increased interest as optical limiters for various applications, although many of them suffer from reduced efficiencies at high-light fluences due to photoinduced deterioration. The nonlinear optical properties of ferrite core/shell nanoparticles showing their robustness for ultrafast optical limiting applications are reported. At 100 fs ultrashort laser pulses the effective two-photon absorption (2PA) coefficient shows a nonmonotonic dependence on the shell thickness, with a maximum value obtained for thin shells. In view of the local electric field confinement, this indicates that core/shell is an advantageous morphology to improve the nonlinear optical parameters, exhibiting excellent optical limiting performance with effective 2PA coefficients in the range of 10-12 cm W-1 (100 fs excitation), and optical limiting threshold fluences in the range of 1.7 J cm-2 . These values are comparable to or better than most of the recently reported optical limiting materials. The quality of the open aperture Z-scan data recorded from repeat measurements at intensities as high as 35 TW cm-2 , indicates their considerably high optical damage thresholds in a toluene dispersion, ensuring their robustness in practical applications. Thus, the high photostability combined with the remarkable nonlinear optical properties makes these nanoparticles excellent candidates for ultrafast optical limiting applications.

Interaction of an Ultra-Short Laser Pulse and Ultra-Intense with a Dielectric

In this work, we dedicated to the presentation of our results concerning the evolution of the electron density in the conduction band and the optical damage threshold (OBT). A study of the influence of the initial electronic density on the electron density in the conduction band and on the threshold of optical damage will also be presented. The main objective of this work is the theoretical study of optical damage of dielectric Materials like: Silicate by using a technique based on ultra-short and high-density laser pulses. The mains theoretical models about the OBT technique given in the literature are also studied. A new theoretical model with several improvements is proposed. This model takes into account the recombination’s mechanism with three holes. New numerical software has been developed in order to solve the PDE systems of our theoretical model using MATLAB simulation. The contribution of different mechanisms with OBT has been studied numerically. The obtained results showed that recombination mechanism with three holes plays an important role to estimate the density of free electrons and the OBT. We showed in our model that the recombination mechanisms reduce the electron density in the band of conduction is therefore increasing the threshold of optical damage (OBT). The predictions of the code developed in this study have been successfully compared to different experimental measurements of thresholds of breakdown in silica. The found results have a good agreement with experimental results.

Femtosecond laser-induced damage threshold in snow micro-structured targets

Enhanced acceleration of protons to high energy by relatively modest high power ultra-short laser pulses, interacting with snow micro-structured targets was recently proposed. A notably increased proton energy was attributed to a combination of several mechanisms such as localized enhancement of the laser field intensity near the tip of $1~\unicode[STIX]{x03BC}\text{m}$ size whisker and increase in the hot electron concentration near the tip. Moreover, the use of mass-limited target prevents undesirable spread of absorbed laser energy out of the interaction zone. With increasing laser intensity a Coulomb explosion of the positively charged whisker will occur. All these mechanisms are functions of the local density profile and strongly depend on the laser pre-pulse structure. To clarify the effect of the pre-pulse on the state of the snow micro-structured target at the time of interaction with the main pulse, we measured the optical damage threshold (ODT) of the snow targets. ODT of $0.4~\text{J}/\text{cm}^{2}$ was measured by irradiating snow micro-structured targets with 50 fs duration pulses of Ti:Sapphire laser.

Фотоиндуцированная обратимая локальная деформация рельефа поверхности в объемных монокристаллах TlInSe-=SUB=-2-=/SUB=-, TlGaTe-=SUB=-2-=/SUB=- и TlSe

AbstractGiant macroscopic expansion of the surface relief, localized within a laser spot size, has been observed in bulk single crystals of TlInSe_2, TlGaTe_2, and TlSe at room temperature and laser radiation densities lower by at least two orders of magnitude than the material optical damage threshold. Quantitative estimations of the deformation magnitude in this local region were obtained using an interference dilatometer. The photon absorption length was determined with the aid of spectroscopic ellipsometry. It is established that the surface deformation amounts to 2.6 × 10^–3 at a laser radiation intensity of 19 mW/mm^2. The observed phenomenon has a thermal nature and is probably related to a low thermal conductivity of the materials studied.

Four-wave mixing and nonlinear parameter measurement in a gallium-nitride ridge waveguide

Gallium-nitride (GaN) is a promising material platform for integrated electro-optic devices due to its wide direct bandgap, pronounced nonlinearities and high optical damage threshold. Low-loss ridge waveguides in GaN layers were recently demonstrated. In this work, we provide the first report of four-wave mixing in a GaN waveguide at telecommunication wavelengths, and observe comparatively high nonlinear propagation parameters. The nonlinear coefficient of the waveguide is measured as 1.6 ± 0.45 [W × m]−1, and the corresponding third-order nonlinear parameter of GaN is estimated as 3.4 ± 1e-18 [m2/W]. The results suggest that GaN waveguides could be instrumental in nonlinear-optical signal processing applications.

Highly Doped Phosphate Glass Fibers for Compact Lasers and Amplifiers: A Review

In recent years, the exploitation of compact laser sources and amplifiers in fiber form has found extensive applications in industrial and scientific fields. The fiber format offers compactness, high beam quality through single-mode regime and excellent heat dissipation, thus leading to high laser reliability and long-term stability. The realization of devices based on this technology requires an active medium with high optical gain over a short length to increase efficiency while mitigating nonlinear optical effects. Multicomponent phosphate glasses meet these requirements thanks to the high solubility of rare-earth ions in their glass matrix, alongside with high emission cross-sections, chemical stability and high optical damage threshold. In this paper, we review recent advances in the field thanks to the combination of highly-doped phosphate glasses and innovative fiber drawing techniques. We also present the main performance achievements and outlook both in continuous wave (CW) and pulsed mode regimes.

High‐power single spatial mode superluminescent diodes at 675 nm

The optimisation of AlGaInP/GaInPAs MQW heterostructure metal-organic chemical vapour deposition growth as well as the improvements of active channel formation and P-contact deposition technologies is shown to enable a significantly increased external differential efficiency up to 0.5 mW/mA and catastrophic optical damage threshold up to 50 mW of spatially single-mode superluminescent diodes (SLDs) at central wavelength of 675 nm. Life time tests demonstrated high reliability of new SLDs at continuous wave output power of up to 30 mW. The dependencies of spectral and power characteristics of these SLDs on active channel dimensions are presented. To the best of knowledge, these are the most powerful and broadband SLDs at 675 nm.

Analysis of thresholds of optical damage to the potassium and sodium chloride surface by femtosecond laser pulses

Comparative analysis of optical damage thresholds of potassium and sodium chloride surface by pulses with durations of 80 and 40 fs has been carried out. The critical radiation power in a pulse at the optical damage threshold for the ion crystals studied has been determined. An estimate of the optical damage thresholds of the sodium chloride surface by laser pulses with a duration of 20 fs is presented.

Study of middle infrared difference frequency generation using a femtosecond laser source in LGT.

We demonstrate phase-matched difference frequency generation in the emerging nonlinear crystal La3Ga5.5Ta0.5O14. Tunable wavelengths between 1.4 and 4.7μm are generated by using femtosecond sources. We also report on the measurements of the optical damage threshold in the femtosecond regime and on the nonlinear refractive index n2.

Stability investigation of laser darkened metal surfaces

Pulsed laser irradiation-induced reflectivity decrease of metal surfaces is a well-established phenomenon, which is extensively utilized in numerous applications. Since the stability of these black surfaces is often a demand, we investigated the resistance of darkened copper and titanium surfaces against optical and mechanical damages. For optical stability studies, samples were irradiated by a probe laser beam (λ = 775 nm, FWHM = 150 fs, f = 1 kHz) at different fluences (0–300 mJ/cm2), while the mechanical stability was studied with scratch test using 2.5 µm radius tip and applying normal force in 29.4–147 µN range. The observed reflectivity and morphological changes indicated that the optical damage threshold fluence is 130 and 160 mJ/cm2 for copper and titanium surfaces, respectively. Mechanical damage only in case of copper could be detected in the applied parameter range indicating a scratch hardness of 21.5 MPa.

Efficient method for the measurement of lifetime optical damage performance of thin film coatings from laser damage size analysis.

A laser damage test method based on damage size analysis (DSA) is described that simplifies the derivation of the lifetime optical damage threshold of film materials critical in the design of devices used in high-repetition-rate, high-power laser systems. The DSA method presented here is solely based on imaging to measure the damage site size produced from exposure to a known Gaussian-shaped beam with a fixed, systematically selected fluence well above the ablation threshold. The method locates the damage boundary produced from repeated exposures, using images with a high contrast, and maps it to the beam profile to extract a lifetime laser damage fluence threshold value. We validate the DSA approach using a few relevant transparent film material systems and by comparing it to the standard S/1 laser damage test method. The DSA method can be more efficient and accelerate materials development and validation necessary to support the design of high-power repetition-rated lasers and optoelectronic devices.

1.15 PW-850 J compressed beam demonstration using the PETAL facility.

The Petawatt Aquitaine Laser (PETAL) facility was designed and constructed by the French Commissariat à l'énergie atomique et aux énergies alternatives (CEA) as an additional PW beamline to the Laser MegaJoule (LMJ) facility. PETAL energy is limited to 1 kJ at the beginning due to the damage threshold of the final optics. In this paper, we present the commissioning of the PW PETAL beamline. The first kJ shots in the amplifier section with a large spectrum front end, the alignment of the synthetic aperture compression stage and the initial demonstration of the 1.15 PW @ 850 J operations in the compression stage are detailed. Issues encountered relating to damage to optics are also addressed.

Optical and laser damage threshold studies on 1, 3, 5-triphenylbenzene scintillator crystal grown by Sankaranarayanan-Ramasamy (SR) technique

Unidirectional (<200> plane) 1, 3, 5-triphenylbenzene (3PB) single crystal 150mm long and 25mm diameter was grown by SR technique. The grown crystal was subjected to UV–vis-NIR spectral analysis determine linear optical properties over the range of 200–1100nm. The relevant optical parameters such as transmittance, absorption coefficient, extinction coefficient, band gap energy, reflectance, and refractive index were determined which reveal the suitability of crystal to couple with a photomultiplier tube or other light sensor. The wide band gap energy 3.65eV of the 3PB crystal shows significant transmittance in the Vis and NIR region. The refractive index of the crystal is determined to be constant above 350nm, and it confirms the required parameter to set high light yield. The temperature dependence refractive index was measured in the range of 30–70°C, it illustrates the faster propagation light in the crystal. Third order nonlinear optical parameters of the grown crystal were estimated by Z-scan technique. It showed that the low absorption coefficient and negative refractive index. The second order hyperpolarizability (γ) of 3PB molecule was found to be 8.6411×10−34 esu. The obtained all results in the present work which makes the 3PB crystal promising candidate for optical power limits, optical switching and other nonlinear optical applications. The Laser Damage Threshold (LDT) was determined to be 2.1612 GW/cm2 and it confirms the suitability of crystal for device fabrication.

Passively Q-switched and mode-locked fiber laser research based on graphene saturable absorbers

We introduce a saturable absorber by coating double graphene films on a fusion stretched microfiber waveguide, compare with employing graphene films sandwiched between fiber ferrules that stable Q-switched pulse disappeared at 240 mW pump, it shows feasibility for improved Q-switching operation at higher optical damage threshold (up to 600 mW), repetition rate increased from 50.38 to 73.06 kHz and pulse energy from 76.82 to 93.76 nJ, as pump power change from 300 to 500 mW. And our laser produced 1.94 ps mode-locked pulse at ~1560 nm by GMF. Bilayer chemical vapor deposition synthesized graphene was used to enhance the evanescent interaction with the microfiber.

Photodetector based on Vernier-Enhanced Fabry-Perot Interferometers with a Photo-Thermal Coating

We present a new type of fiber-coupled photodetector with a thermal-based optical sensor head, which enables it to operate even in the presence of strong electro-magnetic interference and in electrically sensitive environments. The optical sensor head consists of three cascaded Fabry-Perot interferometers. The end-face surface is coated with copper-oxide micro-particles embedded in hydrogel, which is a new photo-thermal coating that can be readily coated on many different surfaces. Under irradiation, photons are absorbed by the photo-thermal coating, and are converted into heat, changing the optical path length of the probing light and induces a resonant wavelength shift. For white-light irradiation, the photodetector exhibits a power sensitivity of 760 pm/mW, a power detection limit of 16.4 μW (i.e. specific detectivity of 2.2 × 105 cm.√Hz/W), and an optical damage threshold of ~100 mW or ~800 mW/cm2. The response and recovery times are 3.0 s (~90% of change within 100 ms) and 16.0 s respectively.

Large area growth of monolayer MoS2 film on quartz and its use as a saturable absorber in laser mode-locking

Monolayer MoS2 film on quartz was fabricated by a home-made three-temperature zone chemical vapor deposition method. The photo, AFM image, Raman spectroscopy and HRTEM image showed that high quality as-grown MoS2 film completely covered the whole quartz substrate of a few cm2. A Nd:YVO4 laser with mode-locking operation was obtained by using the monolayer MoS2 on quartz as the saturable absorber (SA). To the best of our knowledge, this is the first report on large-area growth of high quality monolayer MoS2 film on transparent quartz substrate, and the first time that the CVD MoS2 SA was used in mode-locked solid state lasers. Because of the large area, high transmission, low non-saturable loss and high optical damage threshold of this material, it is very suitable for application in mode-locked solid state lasers.