Compression Of Laser Pulses Research Articles

Carrier-envelope phase-stabilized ultrashort pulses from a gas-filled multi-pass cell

Few-cycle laser pulses at a high repetition rate with a stable carrier-envelope phase are required for next-generation attosecond time-resolved spectroscopies. One way to generate these pulses is the nonlinear compression of laser pulses via gas-filled hollow-core fibers. Recently, an alternative approach based on multi-pass cells (MPCs) has been shown to be very efficient for post-compression of turn-key, industrial-grade, high average power Yb-doped solid-state laser amplifiers. However, to expand the system for exploring strong-field laser applications, its carrier-envelope phase stability needs to be demonstrated in the compressed pulses. In this Letter, we present the generation of carrier-envelope phase-stabilized 40 fs pulses with 380 μJ energy at 50 kHz by compressing the output of a Yb:KGW amplifier in a gas-filled MPC. Comparable short-term carrier-envelope phase errors of 412 and 435 mrad root mean square were observed from the amplifier and MPC, respectively, indicating that the phase stability of the amplified pulses is well-maintained during pulse compression in the MPC.

Plasma-grating-based laser pulse compressor.

To avoid damage in high-power laser systems, a chirped plasma-based grating is proposed for compressing laser pulses that have been previously stretched and amplified. This chirped grating is generated through the interaction of chirped pump laser pulses in a plasma slab. Particle-in-cell (PIC) simulations demonstrate that the grating exists for a duration sufficient to be utilized in the final chirped pulse amplification (CPA) stage. The generation of the grating is quite flexible, as several parameters can be adjusted, such as plasma density, chirp, length, and intensity of the pump laser. To begin, the structure of the grating is analyzed in terms of ponderomotive effects of the pump laser pulses. The primary application of the chirped plasma-based grating lies in compressing laser pulses to large amplitudes and short durations after they have been stretched and amplified beforehand. The compression factor is explored in connection with potential grating parameters. Reflectivity and effective bandwidth of chirped plasma gratings are parameters to be optimized. However, the grating spectral bandwidth can only be increased at the expense of reflectivity. The PIC results are made understandable through model calculations based on coupled mode equations.

Applications of Microstructured Optical Fibers in Ultrafast Optics: A Review

With the development of laser technology, microstructured optical fibers (MOFs) have become an important part of ultrafast optics, providing excellent platforms for ultrafast laser pulse generation, amplification, and compression, promoting the development of fiber laser systems to generate high power, high pulse energy, and few-cycle duration pulses. MOFs extend the ultrafast laser spectrum to the vacuum ultraviolet (VUV) and even extreme ultraviolet (EUV) regions based on dispersive wave emission and high harmonic generation, as well as to the mid-infrared region based on soliton self-frequency shift (SSFS), contributing compact and low-cost light sources for precision microscopy and spectroscopy. In this paper, first several common types of MOFs are introduced, then the various applications of MOFs in ultrafast optics are discussed, mainly focusing on the aspects of ultrafast laser pulse scaling in pulse energy and spectral bandwidth, and finally the possible prospects of MOFs are given.

Fluorescence and lasing of neutral nitrogen molecules inside femtosecond laser filaments in air: mechanism and applications.

High power femtosecond laser pulses launched in air undergo nonlinear filamentary propagation, featuring a bright and thin plasma channel in air with its length much longer than the Rayleigh length of the laser beam. During this nonlinear propagation process, the laser pulses experience rich and complex spatial and temporal transformations. With its applications ranging from supercontinuum generation, laser pulse compression, remote sensing to triggering of lightning, the underlying physical mechanism of filamentation has been intensively studied. In this review, we will focus on the fluorescence and cavity-free lasing effect of the plasma filaments in air. The different mechanisms underlying the fluorescence of the excited neutral nitrogen molecules will be throughly examined and it is concluded that the electron collision excitation is the dominant channel for the formation of the excited nitrogen molecules. The recently discovered "air lasing" effect, a cavity-free bidirectional lasing emission emitted by the filaments, will be introduced and its main properties will be emphasized. The applications of the fluorescence and lasing effect of the neutral nitrogen molecules will be introduced, with two examples on spectroscopy and detection of electric field. Finally, we discuss the quenching effect of the lasing effect in atmosphere and the mechanisms responsible will be analyzed. An outlook for the achievement of backward lasing in air will be briefly presented.

Effektivnoe uskorenie elektronov femtosekundnymi lazernymi impul'sami umerennoy moshchnosti

The relativistic self-trapping of a laser pulse is an efficient mechanism for the acceleration of electrons, whichallows one to achieve an extreme charge of a high-energy particle beam and the corresponding conversioncoefficient of laser energy. It has been shown that the compression of the femtosecond laser pulse in thisregime using the innovative compression after compressor approach (CafCA) [E.A. Khazanov,S.Yu. Mironov, and G. Mourou, Phys. Usp. 62, 1096 (2019)] to extremely short durations keeping the energyof the laser beam significantly increases the efficiency of particle acceleration. This effect has been illustratedon the example of the Multitera laser facility for the project implemented at the Russian National Center forPhysics and Mathematics.

Efficient Acceleration of Electrons by Moderate-Power Femtosecond Laser Pulses

The relativistic self-trapping of a laser pulse is an efficient mechanism for the acceleration of electrons, which allows one to achieve an extreme charge of a high-energy particle beam and the corresponding conversion coefficient of laser energy. It has been shown that the compression of the femtosecond laser pulse in this regime using the innovative compression after compressor approach (CafCA) [E.A. Khazanov, S.Yu. Mironov, and G. Mourou, Phys. Usp. 62, 1096 (2019)] to extremely short durations keeping the energy of the laser beam significantly increases the efficiency of particle acceleration. This effect has been illustrated on the example of the Multitera laser facility for the project implemented at the Russian National Center for Physics and Mathematics.

Laser pulse compression by a density gradient plasma for exawatt to zettawatt lasers

We propose a new method of compressing laser pulses to ultrahigh powers based on spatially varying dispersion of an inhomogeneous plasma. Here, compression is achieved when a long, negatively frequency-chirped laser pulse reflects off the density ramp of an over-dense plasma slab. As the density increases longitudinally, high-frequency photons at the leading part of the laser pulse penetrate more deeply into the plasma region than lower-frequency photons, resulting in pulse compression in a similar way to that by a chirped mirror. Proof-of-principle simulations performed using particle-in-cell simulation codes predict compression of a 2.35 ps laser pulse to 10.3 fs—a ratio of 225. As plasma is robust and resistant to damage at high intensities—unlike solid-state gratings commonly used in chirped-pulse amplification—the method could be used as a compressor to reach exawatt or zettawatt peak powers.

Dense plasma diagnostics with a Nomarski interferometer using a frequency-tripled Ti:sapphire laser

An overdense plasma is considered as a new tool for high-power laser pulse compression. For this purpose, a high density plasma was generated by illuminating an intense fs Ti:sapphire laser pulse onto a surface of an aluminum disk and its spatio-time-resolved dynamics was investigated by a Nomarski interferometer. To probe the laser-produced high density plasma, the original Ti:sapphire laser pulse with a wavelength of 800 nm was frequency-tripled and the UV laser pulse of 266 nm in wavelength was used in the interferometer. It turned out that the fs UV laser interferometer can provide a fairly high density information up to 8.5 × 1020 cm-3. Our experimental result shows that the initial high density plasma near the solid target surface expands rapidly and its density profile in space is gradually reduced to exponential in the ns time scale. This result will provide an important information towards the next step for experimental demonstration of the laser pulse compression using a plasma.

Beam smoothing by introducing spatial dispersion for high-peak-power laser pulse compression.

Post-compression can effectively further improve the peak power of laser pulses by shortening the pulse duration. Which has been investigated in various ranges of energy and central wavelength. However, the spatial intensity profile of high-peak-power laser pulses is generally inhomogeneous due to pump lasers, imperfect optical components, and dust in the optical layout. In post-compression, the B-integral is proportional to intensity, and wavefront distortions are induced in the spectral broadening stage, leading to a decrease in focusing intensity. Moreover, the beam intensity may be strongly modulated and beam inhomogeneity will be intensified in this process, causing damage to optical components and limiting the achievement of high peak power enhancement. In this study, to address these challenges, the laser pulse is first smoothed by introducing spatial dispersion using prism pairs or asymmetric four-grating compressors, and then the smoothed pulse is used for post-compression. The simulation results indicate that this method can effectively remove hot spots from laser pulses and maintain high peak power enhancement in post-compression.

A simple intra-beam alignment setup for tiled grating assembly based laser pulse compressor of high energy ultrashort pulse laser systems

A simple intra-beam alignment setup for tiled grating assembly based laser pulse compressor of high energy ultrashort pulse laser systems

Influence of embedded NiO-nanoparticles on the nonlinear absorption of tungsten disulfide nanolayers

2D transition metal dichalcogenides possess fascinating properties due to their direct bandgap, strong spin-orbit coupling, and promising electronic/mechanical properties. In this work, we synthesized pure tungsten disulfide (WS2) nanolayers and NiO nanoparticles (NPs) decorated in few-layered WS2 and measured the third-order nonlinear optical properties using femtosecond Z-scan measurements. The open aperture Z-scan data illustrated that the inclusion of NiO nanoparticles into the WS2 layers increases the nonlinear absorption at 800 and 400 nm wavelengths. Furthermore, we observed the switchability of the nonlinear absorption from saturable absorption to two-photon absorption or reverse saturable absorption by changing the pump intensity. Thus, the embedded NiO NPs played a crucial role in the variation of intensity-dependent nonlinear absorption mechanism of WS2 nanolayers and thus can be helpful for various optical applications such as laser pulse compression and optical limiting to prevent over-exposure of protective photosensitive sensors by intense ultrashort laser pulses.

Compression of Few-Microjoule Femtosecond Pulses in a Hollow-Core Revolver Fiber

Gas-filled hollow-core fibers are a convenient tool for laser pulse compression down to a few-cycle duration. The development of compact, efficient and high quality compression schemes for laser pulses of relatively low μJ-level energies is of particular interest. In this work, temporal pulse compression based on nonlinear spectral broadening in a xenon-filled revolver fiber followed by a chirped mirror system is investigated. A 250 fs pulse at a central wavelength of 1.03 μm is compressed to 13.3 fs when the xenon pressure was tuned to provide zero group velocity dispersion near 1.03 μm. The energies of input and compressed pulses are 3.8 and 2.7 μJ, respectively. The compression quality factor of 1.8 is achieved.

Gain characteristics of stimulated Brillouin scattering in fused silica.

Stimulated Brillouin scattering (SBS) is a non-linear process which has the capacity to improve the beam quality and pulse characteristics of laser beams. In this paper, we theoretically and experimentally study the process of SBS in fused silica. In particular, we examine the energy reflection and pulse compression of input laser pulses as functions of focus position, pump energy and beam diameter. We utilized coupled wave equations and a distributed noise model to simulate the reflected energy and time waveform under different gain parameters. An experimental system is constructed and used to qualify the numerical simulations. The results reveal that the threshold for the SBS process and the energy reflectivity significantly change with laser focus position under the same pump and focusing parameters. Ultimately, the gain characteristics of the SBS material is the primary factor that influences the SBS output. This work presented here offers insight into the operation of short-length solid-state SBS lasers and serves as a basis for the design and optimization of such systems.

Single thin-plate compression of multi-TW laser pulses to 3.9 fs.

Post-compression of 12-fs laser pulses with multi-TW peak power from an optical parametric chirped pulse amplification (OPCPA) system was performed by using a single thin fused silica plate in a vacuum. By optimizing the input pulses in both spatial and temporal domains, after compression with customized chirped mirrors, we achieved pulses as short as 3.87 fs, in combination with 12-mJ energy. The spatio-spectral quality of the post-compressed pulses was thoroughly analyzed. The generated 1.4-cycle pulses pave the way for next generation attosecond and particle acceleration experiments.

A New Insight into High-Aspect-Ratio Channel Drilling in Translucent Dielectrics with a KrF Laser for Waveguide Applications.

A new insight into capillary channel formation with a high aspect ratio in the translucent matter by nanosecond UV laser pulses is discussed based on our experiments on KrF laser multi-pulse drilling of polymethyl methacrylate and K8 silica glass. The proposed mechanism includes self-consistent laser beam filamentation along a small UV light penetration depth caused by a local refraction index increase due to material densification by both UV and ablation pressure, followed by filamentation-assisted ablation. A similar mechanism was shown to be realized in highly transparent media, i.e., KU-1 glass with a multiphoton absorption switched on instead of linear absorption. Waveguide laser beam propagation in long capillary channels was considered for direct electron acceleration by high-power laser pulses and nonlinear compression of excimer laser pulses into the picosecond range.

Laser compression via fast-extending plasma gratings

A method is proposed for compressing laser pulses by fast-extending plasma gratings (FEPGs), which are created by ionizing a hypersonic wave generated by stimulated Brillouin scattering in a background gas. Ionized by a short laser pulse, the phonon forms a light-velocity FEPG to fully reflect a resonant pump laser. As the reflecting surface moves with the velocity of light, the reflected pulse is temporally overlapped and compressed. One- and two-dimensional fully kinetic particle-in-cell simulations with a laser wavelength of 1 µm show that in this regime, a pump pulse is compressed from 10–40 ps to 7–10 fs (i.e., a few optical cycles), with a two-dimensional transfer efficiency up to 60%. This method is a promising way to produce critical laser powers while avoiding several significant problems that arise in plasma-based compressors, including an unwanted linear stage, major plasma instabilities, and the need for seed preparation.

High-repetition-rate, quarter acoustic wave oscillation period pulse compression using transient stimulated Brillouin scattering.

In this work we demonstrate the compression of laser pulses at a high repetition rate, using transient stimulated Brillouin scattering (SBS). Output pulses with pulse durations close to the quarter-acoustic wave oscillation period (τf) was obtained. We find that the primary factors which limit the compression of pulses under high repetition-rate, transient conditions are the inherently low gain in the transient regime, thermal accumulation within the SBS medium and optical breakdown. We show that short phonon lifetimes can suppress the trailing edge amplification of the output pulse, while also reducing the threshold and improve energy efficiency. In this work, we demonstrate the generation of output laser pulses with a repetition-rate of 200 Hz and an average pulse duration of 1.08τf using the electronic-fluorinated liquid FC-43. Due to the fast decay of the acoustic field, compressed pulses with duration <τf were also observed. We also demonstrate efficient output of pulses with repetition-rate of 200 Hz and energy efficiency of up to 40% using the heat transfer fluid HT-230.

Plasma Transmission Gratings for Compression of High-Intensity Laser Pulses

Plasma Transmission Gratings for Compression of High-Intensity Laser Pulses

Temporal compression of high-power IR laser pulses in a KDP crystal.

It is shown that a KDP crystal can be used for temporal compression of powerful pulses of the near-IR range. A method of searching for laser beam and crystal parameters suitable for compression is proposed. Temporal compression of laser pulses at a central wavelength of 1034 nm from 266 fs to 94 fs during propagation along the optical axis in a 21 cm thick KDP crystal is demonstrated experimentally.

Real-time adaptive ultrashort pulse compressor for dynamic group delay dispersion compensation.

The optical dispersion effect in ultrafast pulse laser systems broadens the laser pulse duration and reduces the theoretical peak power. The present study proposes an adaptive ultrashort pulse compressor for compensating the optical dispersion using a direct optical-dispersion estimation by spectrogram (DOES) method. The DOES has fast and accurate computation time which is suitable for real time controller design. In the proposed approach, the group delay dispersion (GDD) and its polarity are estimated directly from the delay marginal of the trace obtained from a single-shot frequency-resolved optical gating (FROG). The estimated GDD is then processed by a closed-loop controller, which generates a command signal to drive a linear deformable mirror as required to achieve the desired laser pulse compression. The dispersion analysis, control computation, and deformable mirror control processes are implemented on a single field programmable gate array (FPGA). It is shown that the DOES dispersion computation process requires just 0.5 ms to complete. Moreover, the proposed pulse compressor compensates for both static dispersion and dynamic dispersion within five time steps when closed-loop controller is performed at a frequency of 100 Hz. The experimental results show that the proposed pulse compressor yields an effective fluorescence intensity improvement in a multiphoton excited fluorescence microscope (MPEFM).