Showing papers on "Diffraction grating published in 2021"

Broadband Directional Control of Thermal Emission

Abstract: We experimentally realize broadband directional thermal emitters by introducing two subwavelength photonic structures consisting of multiple oxides that exhibit epsilon-near-zero (ENZ) regions at long-wave infrared wavelengths.

Azimuthal modulation of electromagnetically induced grating using structured light.

Abstract: We propose a theoretical scheme for creating a two-dimensional Electromagnetically Induced Grating in a three-level $$\Lambda $$ -type atomic system interacting with a weak probe field and two simultaneous position-dependent coupling fields—a two dimensional standing wave and an optical vortex beam. Upon derivation of the Maxwell wave equation, describing the dynamic response of the probe light in the atomic medium, we perform numerical calculations of the amplitude, phase modulations and Fraunhofer diffraction pattern of the probe field under different system parameters. We show that due to the azimuthal modulation of the Laguerre–Gaussian field, a two-dimensional asymmetric grating is observed, giving an increase of the zeroth and high orders of diffraction, thus transferring the probe energy to the high orders of direction. The asymmetry is especially seen in the case of combining a resonant probe with an off-resonant standing wave coupling and optical vortex fields. Unlike in previously reported asymmetric diffraction gratings for PT symmetric structures, the parity time symmetric structure is not necessary for the asymmetric diffraction grating presented here. The asymmetry is due to the constructive and destructive interference between the amplitude and phase modulations of the grating system, resulting in complete blocking of the diffracted photons at negative or positive angles, due to the coupling of the vortex beam. A detailed analysis of the probe field energy transfer to different orders of diffraction in the case of off-resonant standing wave coupling field proves the possibility of direct control over the performance of the grating.

Recent advancements in fiber Bragg gratings based temperature and strain measurement

Abstract: Fiber Bragg Gratings or FBGs have achieved significant attention towards sensing and communication applications due to their outstanding advantages. Due to its high sensitivity towards various design parameters, it is now widely used to measure different physical and chemical parameters in various industrial sectors, including harsh environment applications. This review presents a comparative study of different FBG-based temperature and strain sensors reported in recent years. The analytical formulation for such sensors is also presented in brief. Necessary numerical simulation results are incorporated. For FBG based temperature sensors, both low and high range are considered. Similarly, for FBG-based strain sensors, both uniform and non-uniform strain are considered and discussed in brief. Apart from the sensing applications, new variants of FBG like secondary gratings and Random Optical Grating by Ultraviolet or ultrafast laser Exposure (ROGUE) gratings are also discussed.

Toward optical coherence tomography on a chip: in vivo three-dimensional human retinal imaging using photonic integrated circuit-based arrayed waveguide gratings.

Abstract: In this work, we present a significant step toward in vivo ophthalmic optical coherence tomography and angiography on a photonic integrated chip. The diffraction gratings used in spectral-domain optical coherence tomography can be replaced by photonic integrated circuits comprising an arrayed waveguide grating. Two arrayed waveguide grating designs with 256 channels were tested, which enabled the first chip-based optical coherence tomography and angiography in vivo three-dimensional human retinal measurements. Design 1 supports a bandwidth of 22 nm, with which a sensitivity of up to 91 dB (830 µW) and an axial resolution of 10.7 µm was measured. Design 2 supports a bandwidth of 48 nm, with which a sensitivity of 90 dB (480 µW) and an axial resolution of 6.5 µm was measured. The silicon nitride-based integrated optical waveguides were fabricated with a fully CMOS-compatible process, which allows their monolithic co-integration on top of an optoelectronic silicon chip. As a benchmark for chip-based optical coherence tomography, tomograms generated by a commercially available clinical spectral-domain optical coherence tomography system were compared to those acquired with on-chip gratings. The similarities in the tomograms demonstrate the significant clinical potential for further integration of optical coherence tomography on a chip system. The goal of an optical coherence tomography (OCT) imaging system that is integrated on a photonic chip has taken a step closer to reality. Elisabet Rank and coworkers from Austria have shown that arrayed waveguide gratings (AWGs), integrated-optical devices commonly used to separate different wavelength channels in an optical communications system, can be used to replace diffraction gratings in an OCT system. Several designs of silicon nitride AWGs with 256 channels in the near-infrared were fabricated and then tested in an OCT system which was able to capture in-vivo tomograms and angiography of the human eye’s retina, with comparable quality to a conventional system. The next stage of the OCT-on-a-chip research will focus on exploring the use of multimode interference structures, integrated photodiodes, and compact light sources.

MEMS gratings and their applications

Abstract: Grating plays an essential role in various optical systems owing to its unique dispersion properties. In recent years, there is increasing demand to miniaturize optical systems for a wide range of ...

Robust multifilament arrays in air by Dammann grating

Abstract: We compare transverse structure evolution and energy deposition into the medium within focused multifilament arrays created using two different types of diffraction optical elements (DOEs): TEM11 phase plate and a Dammann grating. We show that the employment of the Dammann grating provides a robust way to create regular multifilament arrays, which is far less dependent on laser beam quality than one using the phase plate.

Multistep pulse compressor for 10s to 100s PW lasers

Abstract: High-energy tens (10s) to hundreds (100s) petawatt (PW) lasers are key tools for exploring frontier fundamental researches such as strong-field quantum electrodynamics (QED), and the generation of positron-electron pair from vacuum. Recently, pulse compressor became the main obstacle on achieving higher peak power due to the limitation of damage threshold and size of diffraction gratings. Here, we propose a feasible multistep pulse compressor (MPC) to increase the maximum bearable input and output pulse energies through modifying their spatiotemporal properties. Typically, the new MPC including a prism pair for pre-compression, a four-grating compressor (FGC) for main compression, and a spatiotemporal focusing based self-compressor for post-compression. The prism pair can induce spatial dispersion to smooth and enlarge the laser beam, which increase the maximum input and output pulse energies. As a result, as high as 100 PW laser with single beam or more than 150 PW through combining two beams can be obtained by using MPC and current available optics. This new optical design will simplify the compressor, improve the stability, and save expensive gratings/optics simultaneously. Theoretically, the output pulse energy can be increased by about 4 times using the MPC method in comparison to a typical FGC. Together with the multi-beam tiled-aperture combining method, the proposed tiled-grating based tiled-aperture method, larger gratings, or negative chirp pulse based self-compression method, several 100s PW laser beam is expected to be obtained by using this MPC method in the future, which will further extend the ultra-intense laser physics research fields.

Wide-Band/Angle Blazed Dual-Mode Metallic Groove Gratings

Abstract: A simple approach to acquire wide-band/angle blazing operation in 1-D metallic gratings is investigated by means of mode-matching and equivalent circuit analysis The gratings are single-groove perfectly conducting gratings that support two propagating guided modes (opposed to typical single-mode cases) It is shown under what conditions one can achieve blazing over a wide range of frequencies and angles Most importantly, it is identified what governs blazing, in particular the true matching condition that needs to be satisfied, and how the structures’ multiple resonances play role in achieving such matching and tailoring the bandwidth Parameters of the proposed equivalent circuit model for the case of the transverse magnetic (TM) polarization are analytically derived The accuracy of the models is verified through a comparison against the results of full-wave simulations The procedure to achieve wide-band/angle blazing performance is delineated, and the design parameters are explicitly given It is shown that this structure can strongly transfer the power of the TM polarized incident wave to the −1st diffraction order with a fractional bandwidth of ≈50% at working frequency $f_{0}=10$ GHz and for −10 dB specular reflection loss, thus realizing a broadband structure From the circuit model, an insightful discussion is presented at various mechanisms at play when Bragg and off-Bragg blazing occurs and fully justifies the behavior of the device The proposed technique opens up new vistas in a wide range of applications, such as spectroscopy, Littrow cavities, beam splitters, refractive index biosensors, and frequency scanned antenna reflectors

Highly Sensitive Diffraction Grating of Hydrogels as Sensors for Carbon Dioxide Detection

Abstract: A diffraction grating of a stimulus-responsive hydrogel was fabricated for the detection of CO2 with a low detection limit. The hydrogel consisted of dimethylaminopropyl methacrylamide (DMAPMA), me...

Microfabrication and Surface Functionalization of Soda Lime Glass through Direct Laser Interference Patterning.

Abstract: All-purpose glasses are common in many established and emerging industries, such as microelectronics, photovoltaics, optical components, and biomedical devices due to their outstanding combination of mechanical, optical, thermal, and chemical properties. Surface functionalization through nano/micropatterning can further enhance glasses’ surface properties, expanding their applicability into new fields. Although laser structuring methods have been successfully employed on many absorbing materials, the processability of transparent materials with visible laser radiation has not been intensively studied, especially for producing structures smaller than 10 µm. Here, interference-based optical setups are used to directly pattern soda lime substrates through non-lineal absorption with ps-pulsed laser radiation in the visible spectrum. Line- and dot-like patterns are fabricated with spatial periods between 2.3 and 9.0 µm and aspect ratios up to 0.29. Furthermore, laser-induced periodic surface structures (LIPSS) with a feature size of approximately 300 nm are visible within these microstructures. The textured surfaces show significantly modified properties. Namely, the treated surfaces have an increased hydrophilic behavior, even reaching a super-hydrophilic state for some cases. In addition, the micropatterns act as relief diffraction gratings, which split incident light into diffraction modes. The process parameters were optimized to produce high-quality textures with super-hydrophilic properties and diffraction efficiencies above 30%.

High-stability, linearly polarized mode-locking generation from a polarization-maintaining fiber oscillator around 2.8 µm.

Abstract: In this Letter, a high-stability, linearly polarized mode-locked polarization-maintaining (PM) Er3+-doped fluoride fiber oscillator at ∼2.8µm is presented for the first time, to the best of our knowledge, where an InAs-based semiconductor saturable absorber mirror is used as the mode locker, and a film polarizer is employed for maintaining the linearly polarized oscillation. In the free-running state, stable linearly polarized mode-locked pulses (τ=44ps and P=446mW) at 2.795 µm, with a high polarization extinction ratio of >23dB and a low integrated relative intensity noise of 0.087% [1 Hz–10 MHz], have been achieved, which can be strongly immune to external mechanical perturbations. By introducing a ruled reflective diffraction grating into the cavity in a Littman configuration, the continuous wavelength tuning of the linearly polarized mode-locked pulses in the range of 2717–2827 nm is obtained as well. To the best of our knowledge, this marks the first demonstration of a linearly polarized PM fiber oscillator in the >2.5µm mid-infrared region.

High-efficiency conversion from waveguide mode to an on-chip beam using a metamaterial engineered Bragg deflector.

Abstract: Diffraction gratings that redirect light propagating in a channel waveguide to an on-chip slab are emerging as important building blocks in integrated photonics. Such distributed Bragg deflectors enable precise shaping of slab confined beams for a variety of applications, including wavelength multiplexing, optical phased array feeding, and coupling interfaces for on-chip point-to-point communications. However, these deflectors suffer from significant losses caused by off-chip radiation. In this Letter, we show, for the first time, to the best of our knowledge, that off-chip radiation can be dramatically reduced by using the single-beam phase matching condition and subwavelength metamaterial refractive index engineering. We present a deflector design with losses below 0.3 dB, opening a path toward new applications of distributed Bragg deflectors in integrated photonics.

Polarization-independent 2×2 high diffraction efficiency beam splitter based on two-dimensional grating

Abstract: Better performances of two-dimensional (2D) grating are required recently, such as polarization independence, high efficiency, wide bandwidth and so forth. In this paper, we propose a 2×2 2D silver cylindrical array grating with excellent polarization-independent high diffraction efficiency (DE) over communication band for beam splitting. The grating was calculated by rigorous coupled wave analysis (RCWA) and can achieve over 24% DE of four first diffraction orders at 1550 nm with nonuniformity of 1.43% in both transverse electric (TE) and transverse magnetic (TM) polarizations, which is a significant improvement over previous reports. The holographic exposure technology, wet chemical development process and electron beam evaporation were used to fabricate the 2D grating. The correctness and accuracy of the calculation are fully verified with the measurement result of fabricated grating. Excellent performances of the 2D splitter we proposed will have great potential for applications in optical communication, semiconductor manufacturing and displacement measurement.

Experimental demonstration of a concave grating for spin waves in the Rowland arrangement

Abstract: We experimentally demonstrate the operation of a Rowland-type concave grating for spin waves, with potential application as a microwave spectrometer. In this device geometry, spin waves are coherently excited on a diffraction grating and form an interference pattern that focuses spin waves to a point corresponding to their frequency. The diffraction grating was created by focused-ion-beam irradiation, which was found to locally eliminate the ferrimagnetic properties of YIG, without removing the material. We found that in our experiments spin waves were created by an indirect excitation mechanism, by exploiting nonlinear resonance between the grating and the coplanar waveguide. Although our demonstration does not include separation of multiple frequency components, since this is not possible if the nonlinear excitation mechanism is used, we believe that using linear excitation the same device geometry could be used as a spectrometer. Our work paves the way for complex spin-wave optic devices-chips that replicate the functionality of integrated optical devices on a chip-scale.

Rectangular multilayer dielectric gratings with broadband high diffraction efficiency and enhanced laser damage resistance.

Abstract: Broadband multilayer dielectric gratings (MDGs) with rectangular HfO2 grating profile were realized for the first time using a novel fabrication process that combines laser interference lithography, nanoimprint, atomic layer deposition and reactive ion-beam etching. The laser-induced damage initiating at the grating ridge was mitigated for two reasons. First, the rectangular grating profile exhibits the minimum electric-field intensity (EFI) enhancement inside the grating pillar compared to other trapezoidal profiles. Second, our etching process did not create nano-absorbing defects at the edge of the HfO2 grating where the peak EFI locates, which is unavoidable in traditional fabrication process. The fabricated MDGs showed a high laser induced damage threshold of 0.59J/cm2 for a Ti-sapphire laser with pulse width of 40 fs and an excellent broadband diffraction spectrum with 95% efficiency over 150 nm in TE polarization.

Common-path intrinsically achromatic optical diffraction tomography

Abstract: In this work we propose an open-top like common-path intrinsically achromatic optical diffraction tomography system. It operates as a total-shear interferometer and employs Ronchi-type amplitude diffraction grating, positioned in between the camera and the tube lens without an additional 4f system, generating three-beam interferograms with achromatic second harmonic. Such configuration makes the proposed system low cost, compact and immune to vibrations. We present the results of the measurements of 3D-printed cell phantom using laser diode (coherent) and superluminescent diode (partially coherent) light sources. Broadband light sources can be naturally employed without the need for any cumbersome compensation because of the intrinsic achromaticity of the interferometric recording (holograms generated by –1st and +1st conjugated diffraction orders are not affected by the illumination wavelength). The results show that the decreased coherence offers much reduced coherent noise and higher fidelity tomographic reconstruction especially when applied nonnegativity constraint regularization procedure.

Optical Grating Techniques for MEMS-Based Spectrometer—A Review

Abstract: This paper examined the innovations of the spectrometers for the measurement of consistency based parameters of the handheld Micro Electronic Mechanical System (MEMS) Spectrometer. Fast, highly sensitive, miniature spectroscopy techniques empowered quick, savvy and effective measures for various applications. In the light spectroscopy-based identification and quantification, advances in the field of wavelength discrimination are significant and essential. The identification of grid parameters and limiting conditions are necessary for the design and fabrication of diffraction gratings, for the spectrometer. This work evaluates the emerging trends in Micro-Spectrometer’s Grating Techniques, focusing on the aspects of grating parameters and the recent developments of grating. The main parameters for evaluating the performance of a grating have been reviewed and found that grating efficiency, groove density, free spectral range and resolving power play a significant part in the grating performance. The fabrication technique employed as well as the materials used in the fabrication process, play a significant role in the efficiency of the grating. Silicon, Silicon dioxide (SiO2), Glass (Silica glass), Poly methyl methacrylate (PMMA), Chromium and Silicon nitride(Si3N4) are the most used materials. The integration of new materials that are ideal for the state-of-the-art semiconductor industry techniques for MEMS fabrication along with a new blazing structure would increase the efficiency of the grating.

Ultra-compact dual-mode mode-size converter for silicon photonic few-mode fiber interfaces

Abstract: Fiber couplers usually take a lot of space on photonic integrated circuits due to the large mode-size mismatch between the waveguide and fiber, especially when a fiber with larger core is utilized, such as a few-mode fiber. We demonstrate experimentally that such challenge can be overcome by an ultra-compact mode-size converter with a footprint of only 10 µm. Our device expands TE0 and TE1 waveguide modes simultaneously from a 1-µm wide strip waveguide to an 18-µm wide slab on a 220-nm thick silicon-on-insulator, with calculated losses of 0.75 dB and 0.68 dB, respectively. The fabricated device has a measured insertion loss of 1.02 dB for TE0 mode and 1.59 dB for TE1 mode. By connecting the ultra-compact converter with diffraction grating couplers, higher-order modes in a few-mode fiber can be generated with a compact footprint on-chip.

Fabrication of custom astronomical gratings for the extreme and far ultraviolet bandpasses

Abstract: Diffraction gratings used in ultraviolet astronomical spectrographs have been made using mechanical ruling or interference lithography. However, required performance for newly developed EUV (10-90 nm) and FUV (100-180 nm) spectrographs can benefit from groove densities, blaze angles, and low-scatter enabled with electron-beam lithography patterning and chemical etching. We report on the fabrication of custom grating prototypes developed at the Nanofabrication Laboratory at Penn State University. The gratings in development for the ESCAPE NASA Small Explorer (Univ. of Colorado/Boulder) involve writing specific patterns of curved grooves with variable line density on flat substrates. The design of the grating within the DEUCE sounding rocket payload involves writing straight grooves on a spherically curved substrate. All gratings are subsequently etched to achieve the specified blaze in the silicon. These efforts are enabling new applications in the field of astronomical UV spectroscopy.

Characterization of a pair of superposed vortex beams having different winding numbers via diffraction from a quadratic curved-line grating

Abstract: In a recent study, we have reported a simple, efficient, and robust method that is based on diffraction in an amplitude parabolic-line linear grating for determination of the topological charge (TC), l, of an optical vortex beam [J. Opt. Soc. Am. B37, 2668 (2020)JOBPDE0740-322410.1364/JOSAB.398143]. Here, we present a demonstration of the application of that method for characterization of a pair of superposed vortex beams having different winding numbers. It is shown that, when two vortex beams, described by Laguerre–Gaussian beams with winding numbers l1 and l2 and radial index p=0, impinge on-axis and collinearly on a diffraction grating having a quadratic curvature on its lines, with a simple analysis of the resulted diffraction patterns at the zero and first order, the TCs and their signs can be determined. The zero-order diffraction pattern shows an interference pattern of the beams. For close values of l1 and l2, it has a petal-like pattern in which the number of spots is equal to |l1−l2|. It is also found that the first-order diffraction pattern depending to the signs of the beams’ TCs shows two different forms. If l1 and l2 have the same signs, the first-order diffraction pattern is only a set of elongated intensity spots. When the signs of l1 and l2 are opposite, the resulted pattern is a (l1+1) by (l2+1) slanted checkered-like matrix of bright spots. In addition, in this work, we use a simple, novel, and initiative method to generate and combine on-axis and collinearly a pair of vortex beams. Finally, a supporting theoretical study is presented that fully confirms the experimental results and simulation of propagation.

Encoding complex amplitude information onto phase-only diffractive optical elements using binary phase Nyquist gratings

Abstract: We reexamine a simple technique for encoding complex amplitude information onto a phase-only spatial light modulator (SLM) The basis for the approach is to spatially vary the diffraction efficiency of a two-dimensional checkerboard binary phase diffraction grating where the period for the Nyquist grating is two pixels As the phase depth of this 2D grating changes spatially, the amount of light diffracted into the zero order can be controlled Unwanted information is encoded onto the first diffraction orders and is directed away from the center This process uses a very simple coding algorithm to generate a complex beam reconstruction on-axis and allows exploiting the full spatial resolution for encoding amplitude However, its experimental realization with the current liquid-crystal on silicon (LCOS) technology is strongly affected by the limitations imposed by the fringing effect in these devices We provide experimental evidence of how this effect impacts the efficiency of diffraction gratings displayed on the SLM We then show how it affects the encoding technique, both in the near field and in the Fourier transform domain, where the limitations imposed by the fringing effect are clearly visible in the form of a focused peak These results provide evidence of the usefulness of the technique but also about the limitations imposed by the current LCOS technology, which do not allow fully exploiting their high resolution Finally, we discuss the performance of these newer LCOS devices compared to other SLMs

Polarized holographic lithography system for high-uniformity microscale patterning with periodic tunability.

Abstract: Periodic microscale array structures play an important role in diverse applications involving photonic crystals and diffraction gratings. A polarized holographic lithography system is proposed for patterning high-uniformity microscale two-dimensional crossed-grating structures with periodic tunability. Orthogonal two-axis Lloyd’s mirror interference and polarization modulation produce three sub-beams, enabling the formation of two-dimensional crossed-grating patterns with wavelength-comparable periods by a single exposure. The two-dimensional-pattern period can also be flexibly tuned by adjusting the interferometer spatial positioning. Polarization states of three sub-beams, defining the uniformity of the interference fringes, are modulated at their initial-polarization states based on a strict full polarization tracing model in a three-dimensional space. A polarization modulation model is established considering two conditions of eliminating the unexpected interference and providing the desired identical interference intensities. The proposed system is a promising approach for fabricating high-uniformity two-dimensional crossed gratings with a relatively large grating period range of 500–1500 nm. Moreover, our rapid and stable approach for patterning period-tunable two-dimensional-array microstructures with high uniformity could be applicable to other multibeam interference lithography techniques.

Design and optimization method of a convex blazed grating in the Offner imaging spectrometer.

Abstract: The convex reflective diffraction grating is an essential optical component in Offner systems, which has been widely used in imaging spectrometers. We propose a new design and optimization method for the convex blazed grating in the Offner imaging spectrometer. The method integrates the macro- and microdesign of the optical system, and it can be used to design and optimize the convex blazed grating with high diffraction efficiency. Traditional geometric optics theory and image quality evaluation methods are used to design the macro-optical structure parameters of the Offner system. And then the incident ray information, such as the incident angle and the polarization states are calculated by using the three-dimensional polarization ray-tracing method. To improve the diffraction efficiency, we combine rigorous coupled wave analysis and a particle swarm optimization algorithm to optimize the microstructure parameters of the convex-blazed grating. Further, a convex-blazed grating in a mid-wave infrared Offner imaging spectrometer is designed as an example to illustrate our design method in detail. The design results indicate that the Offner imaging spectrometer has good imaging quality, and the average diffraction efficiency of the -1st diffraction order of the convex-blazed grating in the spectral coverage 3-5 µm is 82.24%. Compared to the traditional design method, the lowest spectral diffraction efficiency is improved from 59.88% to 69.24%, the highest spectral diffraction efficiency is improved from 90.45% to 91.84%, and the standard deviation is reduced from 7.82 to 6.62.

Polarization-selective splitter with double structure periodic ridges

Abstract: A dual-function beam separation grating with double structure periodic ridges is proposed. The parameters of the grating structure and characteristics of the incident light are all optimized by the finite-element method and rigorous coupled-wave analysis, so the grating can display the polarization-selective characteristic. At the parameter values that will be discussed in Sec. 2, the diffraction efficiency of the zeroth order, first order, and second order for transverse electric (TE) polarization is 32.30%, 32.34% and 32.30%, respectively, and the uniformity is calculated to be 99.88%. For transverse magnetic (TM) polarization, the reflectivity of the zeroth order and second order is 47.23% and 47.24%, respectively, and the uniformity of two ports is 99.97%. Compared with most previously reported polarization-selective beam splitters that achieve single-port output for TE polarization and dual-port output for TM polarization, the grating realizes TE-three/TM-two output with a decent diffraction efficiency uniformity.

Laser Nanostructuring for Diffraction Grating Based Surface Plasmon-Resonance Sensors

Abstract: The surface plasmon resonance properties of highly regular laser-induced periodic surface structures (HR-LIPSSs) on Si, functionalized with Au nanoparticles (NPs), were investigated. In particular, the spectral dependencies of polarized light reflectance at various angles of incidence were measured and discussed. It is found that the deposition of Au NPs on such periodically textured substrates leads to significant enhancement of the plasmon resonance properties, compared to that measured on planar ones. This effect can be used to improve the efficiency of localized-plasmon-resonance-based sensors.

Femtosecond damage experiments and modeling of broadband mid-infrared dielectric diffraction gratings.

Abstract: High peak and average power lasers with high wall-plug efficiency, like the Big Aperture Thulium (BAT) laser, have garnered tremendous attention in laser technology. To meet the requirements of the BAT laser, we have developed low-dispersion reflection multilayer dielectric (MLD) gratings suitable for compression of high-energy pulses for operations at 2 micron wavelength. We carried out 10000-on-1 damage tests to investigate the fluence damage thresholds of the designed MLD gratings and mirrors, which were found between 100-230 mJ/cm2. An ultrashort pulsed laser (FWHM = 53 fs, λ = 1.9 μm) operating at 500 Hz was used in the serpentine raster scans. The atomic force microscope images of the damage sites show blister formation of the underlying layers at lower fluences but ablation of the grating pillars at higher fluences. We simulated the dynamic electronic excitation in the MLD optics with a finite-difference in the time domain approach in 2D. The simulation results agree well with the LIDT measurements and the observed blister formation. This model is able to evaluate the absolute LIDT of MLD gratings.