A method is proposed for third-order dispersion compensation in compressors of femtosecond petawatt laser facilities employing object-image-grating self-tiling technology to prevent the return of the laser beam in amplifying chains. Simulations are performed for functioning and being developed Nd:glass and Ti:sapphire petawatt-level lasers.

By using N-S equations, RNG κ-ε model and discrete phase model of Euler-Lagrange method, numerical simulations on the removal trajectories of contaminant particles of different sizes and types on the mirror surface are conducted with the commercial software Fluent. Benefiting from the simulation results, a useful device which can capture and collect debris from the mirror surface online is built. Ultimately the efficiency of cleaning and cleanliness of transport mirrors are improved. And to some extent, the chances that contaminant particles go into the surrounding environment and further pollute other optical components are reduced.

The image reconstructed in ordinary digital holography was unable to bring out desired resolution in comparison to photographic materials; thus making it less preferable for many interesting applications. A method is proposed to enhance the resolution of digital holography in all directions by placing a random phase plate between the specimen and the electronic camera and then using an iterative approach to do the reconstruction. With this method, the resolution is improved remarkably in comparison to ordinary digital holography. Theoretical analysis is supported by numerical simulation. The feasibility of the method is also studied experimentally.

The heat generated in the cavity of the high power slab laser amplifier makes it less stable and induces a thermal-lens effect which adds a spherical phase distribution to the wave-front of the laser beam. The commonly employed interferometry or Hartmann–Shack sensor based measurements are unable to provide an accurate measurement of the thermal distortion of the gain medium. It is demonstrated that this problem can be solved using a scheme based on ptychographical iterative engine. The complex transmittance of the outgoing laser is obtained by the proposed scheme while the amplifier is set at its turned off and turned on state and the thermal distortion caused by the pumping light is calculated from the obtained transmittance.

Greek ladder is a technique for approximating n C by rational numbers where n is a positive integer and C is a positive real number. For the classical Greek ladder, the value is C . Based on the continued fraction theory and algebraic equation, the classical Greek ladder in a special case can be reduced to the generalized Fibonacci sequence. By means of proper switching and binary, ternary or quaternary phase modulation, here we have successfully designed the various kinds of nano-photonic devices to produce three-dimensional array foci whose focusing properties satisfy the above mathematical characteristics. With this technology, the diffractionlimited array foci are freely designed or distributed under the requirement at the desired multiple focal planes.

For high-power laser facility, sub-beams caused by multiple defects of opitcal component surface with different distributions interfere with each other in the transmission process, bringing about complex changes in beam quality. So it is necessary to make a clear limitation on relative position of defects. On the basis of the diffraction transmission theory, when there are scratches with different spatial distributions on the optical element surfaces, the changes of beam modulation are studied. The influence of scratch depths on the distribution of near field beam modulation is also taken into account. Results show that when two parallel or vertical scratches are on the same or different surfaces of an element. Both of them produce more serious modulation than single scratch, and the maximum modulation degree can be increased to 1.5 times. Meanwhile more strict requirements for scratch depth are put forward. The results can provide reference for the revision of optical element standard and the determination of defects specifications for large- diameter elements in high-power laser systems.

Laser beam far-field alignment as well as frequency-doubling and frequency-tripling crystal adjustment is very important for high-power laser facility. Separate systems for beam and crystal alignment are generally used while the proposed approach by off-axial grating sampling share common optics for these two functions, reducing both space and cost requirements. This detection system has been demonstrated on the National Laser Facility of Israel. The experimental results indicate that the average far-field alignment error is <5% of the spatial filter pinhole diameter, average autocollimation angle error of crystals is <10 μrad, and average frequency-tripling conversion efficiency is 69.3%, which meet the alignment system requirements on the beam direction and crystals.

Influence of charge coupled device (CCD)′ s nonlinear response characteristics on the near-field and far-field beam quality′ s measurement of high power laser system is analyzed. A new calibration method, based on single slit diffraction, is presented to calibrate CCD′ s photoelectric characteristics. Accomplish the calibration of a given CCD and restore the grey level of near-field and far-field energy distribution by the calibration curve in ideal and practical system to observe the influence on the measurement of near-field fill factor (FF) and far-field encircled energy distribution. The restoration shows that in a certain laser system the near-field FF will improve 1% ~2% after the grey level restoration. And it has nearly no influence on the farfield energy distribution parameters.

The wedge-shaped lens is the key and special optical component of the final optics assembly (FOA) in high power laser facility. The wedge-shaped lens wedge angle measurement plays a remarkable role in focusing performance of high power laser. If processing angle and work attitude of the wedge-shaped lens deviate from the specific work angle, big surface deviation will be introduced into the FOA. Special shape of the wedge-shaped lens is not conducive to the measurements of the transmission profile and wedge angle. A set of wedge-shaped lens measurement adjustment programmes is proposed, including measurement of the wedge-shaped lens in processing process, and off-line measurement of wedge-shaped lens during alignment and on-line measurement during the debugging process. The scheme can ensure the processing precision and working attitude of the wedge-shaped lens, guarantee the beam quality and the positioning accuracy of the FOA components of high power laser system.

The temporal shape of laser pulse is very important for most physical experiments at the SGII facility. For monochrome laser, a general approach is to calculate the injected pulse shape by using gain-fluence curve (GFC). But it doesn′t work well under the condition of high fluence or especially complex pulse shape. For different output fluences, a new hybrid algorithm, based on GFC and intelligent algorithm, is applied to solve the inversion problem of pulse shape at the SGII facility. The calculation accuracy is only decided by the number of sampling points in theory. Hybrid algorithm is proved to be robust, high precision and rapid convergent by numerical calculation.

Measurement platform must exhibit a stereoscopic space distribution in diagnostic systems for petawatt lasers to meet the requirement of a periodically poled lithium niobate (PPLN) crystal for light polarization in singlepulse contrast measuring instrument. A mathematical model of a 4D linear matrix is proposed to achieve rapid and accurate beam alignment in picosecond measurement platform. In the petawatt experiments, the alignment algorithm ensures that the near-field and far-field accuracy is less than 0.16 mm and 0.17 mrad, respectively. The motor is adjusted less than three times, and the corresponding elapsed time is in 2 min. The mathematical model meets measurement requirements for alignment accuracy and time. The pulse contrast of the petawatt lasers is obtained from the model. The pulse acquisition probability of the contrast measuring instrument reaches 90% from 10%, to guarantee that the experimental result of pulse contrast can meet the general requirement (more than 106).

The high-power laser beam in the final optics assembly of high-power laser facilities is often modulated by contamination particles, which may cause local high light intensity, thereby increasing the filamentary damage probability for optical components. To study the general design basis for a final optics assembly to decrease the risk of filamentary damage, different-sized contamination particles deposited on a component surface are simulated to modulate a 351-nm laser beam based on the optical transmission theory, and the corresponding simulation results are analyzed statistically in terms of the propagation characteristic and the light field intensity distribution of the modulated laser beam. The statistical results show that component thickness and distance between components can to some extent be optimized to reduce the appearance of local high light intensity, and the general design basis of component thickness and arrangement are given for different control levels of particle sizes. Moreover, the statistical results can also predict the laser beam quality approximately under the existing optics design and environmental cleanliness. The optimized design for final optics assembly based on environmental cleanliness level is useful to prolong the lifetime of optics and enhance the output power of high-power laser facilities.

The problem that the workpieces with different sizes have different surface figures is studied in the continuous polishing process. The surface shape is a little concave and the peak valley (PV) value is 0.336 λ (λ = 632.8 nm) for the φ100 mm workpiece when polished in the 0.69 m continuous polishing machine. However, the φ48 mm workpiece is convex and the PV value is 0.336 λ . The Winkler′s hypothesis and the Preston equation are applied to study the surface shape of the workpiece, then the overturning moment of the workpiece is found to be the main reason for the surface inconformity. The theoretical analysis results show that to the round workpiece, when the product of the friction coefficient between the workpiece and the polishing pad and the resultant force from the separator to the workpiece is larger than 0.125 times diameter of the workpiece, the workpiece will turn to convex. The experiments of workpiece pressing, lubrication and moving down the supporting position of the separator is done. The results show that the consistency isn′t been improved by applying pressure on the workpiece; by adding lubricant to the polishing slurry, the consistency is improved as the surface PV of the φ48 mm workpiece is reduced to 0.128 λ ; and the inconsistency problem is solved as the surface PV of the φ48 mm workpiece is reduced to 0.058 λ and the shape is slightly concave when moving down the supporting position. The results indicate that the friction coefficient between the polishing pad and the workpiece shouldn′t be to large and the supporting position of the separator to the workpiece should as near to the polishing surface as possible in the continuous polishing process.

To probe the electron density distribution of the plasma,double-frequency grating shearing interferometry based on the soft X-ray laser technology is developed.The 13.9 nm Ni-like Ag soft X-ray laser is used as a probe to make attempt on the diagnosis of laser produced plasma from a planar gold wafer target.Clear interference fringes image is achieved,which fully demonstrates the practicability of this technology.However,there are some problems such as the unclear target surface in the image.Analysis indicates the main reasons of these problems and a reasonable solution is proposed to improve this technology.

Aiming at the problems such as difficult to mearsure and bad consistency of the surfaces in polishing long-focus lens array elements by conventional method, the new way using continuous polishing machine is proposed. According to the theoretical research of the continuous polishing system, the surface of the polishing pad can keep spherical. The workpieces with small curvature spherical surfaces can be polished with the character. The adjusting methods of the polishing pad surface curvature are elaborated. According to the experiments of polishing lens array elements with aperture of 45 mm and curvature radius of 57207 mm in 0.69 m continuous polishing machine, the element surface accuracy and consistency are both better than using conventional oscillating polishing method. At last, the range of the curvature radius that can be polished in the continuous polishing machine is discussed and find that the smaller the polishing pad is, the stronger the ability of polishing spherical surface is. The radius of curvature which is polished in 0.8 m diameter can be as amall as 10 m.

High-power laser induced shocks were used to study spall fracture of polycrystalline aluminum at strain rates more than 106/s at “Shenguang-Ⅱ” laser facility.The free surface velocity histories of shock-loaded samples,150 μm thick and with initial temperature from 293 K to 873 K,were recorded using velocity interferometer system for any reflector(VISAR).From the free surface velocity profile ,spall strength and yield stress are calculated,which shows that spall strength declines while yield strength increases with initial temperature increasing.The loaded samples were recovered for metallographic analysis through Laser Scanning Confocal Microscopy.It is found that there are more micro-voids and more bigger voids near the spall plane.Meanwhile,the grain size increases with temperature slowly except the sharp change at 893K(near melting point).Besides,the fracture mechanisms change from mainly intergranular fracture to transgranular fracture with initial temperature increasing.

We propose a type of diffractive optical element, a modified Fibonacci photon sieve (MFiPS), designed by using the Fibonacci sequence with two different initial seed elements. Focusing properties of MFiPS show that it not only has less secondary foci, but also presents two equal intensity foci by optimizing the diameters of pinholes of MFiPS whose ratio of the two focal distances approaches the golden mean. Higher transverse resolution on the two focal spots is improved by using a super-Gaussian amplitude modulation technology.

Thermal effect is still the most serious problem: it restricts the high power and high beam quality of solid laser to be further enhanced. The efficient thermal management is an important approach to suppress the thermal effect. In this paper, the thermal effect in a gas-cooled laser diode pumped multislab Nd:glass amplifier operating at a repetition rate is investigated in detail both theoretically and experimentally. The three-dimensional distributions of temperature, stress, strain, and birefringence are calculated by a finite element analysis. Based on these data, the thermally induced wavefront distortions and depolarization losses are determined with considering six slabs and one laser head. It is revealed that the theoretical data are in good agreement with the experimental results: the total wavefront distortion is 6.77λ and a depolarization loss of more than 90% accumulates over six slabs when the heat deposition is 0.7 W/cm3.

In order to realize the diagnostics for synchronization of multi-ultrashort pulses, a method to diagnose the synchronization of multi-ultrashort pulses is provided and tested. Taking two beams of picoseconds ultrashort pulses for example, the time division multiplexing method is used. Based on the cross-correlation method, the time synchronization between these two pulses is realized at first. Then, the phase difference of the beams within the range of time synchronization is adjusted. By monitoring the focal spot on far- field can implement the phase synchronization of two pulses. In this scheme, the regulation precision of temporal synchronization and phase synchronization is 6.7 fs and 0.007 π, respectively. The adjustable range of temporal and phase module is 333 ps and 150 π, respectively. The experimental results show that by using this diagnostics scheme the diagnostics for synchronization between two ultrashort pulses can realized.

A new photon sieve with Fibonacci sequence is proposed and a focusing and imaging model of the Fibonacci photon sieve (FiPS) is presented based on the Huygens-Fresnel principle.The results show that the FiPS presents two longitudinal foci with the ratio of golden mean.When the diameters of pinholes are equal to 1.165 times the width of corresponding orbits,the intensity of the two foci is almost the same.Compared with the resolution of Fibonacci zone plate (FiZP),FiPS has higher transverse resolution.Finally,higher transverse resolution on the two focal planes is improved by applying Gaussian apodized technology to the numbers of pinholes of FiPS.In consequence of smaller size,lighter weight,more flexible design and bifocal property,the FiPS can be applied to optical switches,nanometer lithography,bionic eyes,multi-focus imaging and ranging,even some new applications such as ranging from X-ray microscopy and THz imaging.

The SG-II-Up laser facility is one of the most important high power laser facilities in china. The maximum output of this facility is studied, and it is improved to 8000J from the design point 5000J.

According to the non-imaging pump style, pump cavity structure with the theoretical maximum coupling efficiency is researched. Multi-lamp non-imaging pump cavities are designed by edge-ray principle and constant string length method. Two calculation models are obtained through the difference of amplifier structures. The Nd∶glass surfaces illumination in the non-imaging and elliptical imaging pump cavity are simulated with the same pump energy. Results show that there are lamp self-absorption and mutualabsorption in the elliptical imaging pump cavity, which affects amplifier′s gain property. To non-imaging pump cavity, the reflector profile avoids light reflecting back to the lamp and reduces the number of reflections. Thus, non-imaging pump cavity can lead to the maximum coupling efficiency and the best pump uniformity.

We report on the experimental realization of Cerenkov sum-frequency generation across the material dispersion in a one-dimensional, periodically poled ferroelectric crystal. Three schemes of sum-frequency generation, confined only in the vicinity of domain walls and in the form of nonlinear Cerenkov radiation, are demonstrated in normal, degenerated, and anomalous-dispersion-like configurations. We exploit their phase-matching geometries, which exhibit a whole scenario of the evolution of Cerenkov radiation varying with the dispersion relationship among the interaction waves. In addition, two sets of conical sum-frequency generation with different radius and center are demonstrated, which result from scattering assistant phase-matching processes.

The evolution of hot image formation through medium with gain in consideration of the effect of spatialfilter is theoretically and numerically investigated. Based on the linear diffraction theory and small-scale self-focusing theory of Bespalov and Talanov, intensity distribution of hot image in conjugate planeis derived analytically. Then, the peak intensity of hot image for different medium gain and differentpinhole sizes are discussed in detail, the results show theoretical analysis is mostly approximate to thenumerical simulations, furthermore, it is found that suppressing effect on peak intensity ratio with smallgain coefficient is larger than that with bigger ones for determined pinhole size.

The non-collinear phase-matching of 808 nm centered optical parametric amplification(OPA) is analyzed in detail in potassium dideuterium phosphate (DKDP) crystal. Phase-matching parameters for various deuteration DKDP crystals are calculated based on the concepts. Optical parametric chirped pulse amplifier(OPCPA) based on 95% deuteration DKDP crystal is designed and the output characteristics are simulated by OPA coupled wave equations for further discuss. It is concluded that DKDP crystals higher than 90% deuteration level can be utilized in ultra-short high power laser systems with compressed pulses broader than 30 fs. The disadvantage is that the acceptance angles are small, increasing the difficulty of engineering regulation.

In ptychographical imaging with X-ray or electron beam, the recorded speckle intensity pattern of far field diffraction was often saturated by the presence of strong zeroth-order which was undesirable. A beam-stop was widely used to block the area of strong central diffraction in the pattern. The image was then reconstructed by disregarding the diffraction constraints within that area where inaccuracies exists due to saturation or blocking of the beam. Though reconstructions were obtained in this way by omitting saturation regions, the rationale behind this method was not discussed in detail and its effect on the final image quality was not studied. The physics of this method was analyzed theoretically and experimentally in this study. The convolution effect between illumination and object functions was able to retrieve and bring back the information lost in the blocked or saturated area from its neighborhood. This was possible while the saturated or blocked area was not wider than the spectral width of illumination, and once it exceeds this minimum, the quality of reconstruction would degrade seriously. The theoretical model was verified by numerical simulations and experiments.

A consistent Riccati expansion (CRE) method is developed for a special Kuramoto–Sivashinsky (KS) equation and we prove the general KS equation is non-CRE solvable. Furthermore, we obtain the soliton–cnoidal wave interaction solution of the special KS equation.

For the Fizeau optical interferometric telescope system, the co-phasing detection of piston errors between subapertures plays an important role in realizing the high resolution of system. In this paper, the relationship between piston error and the main peak displacement of monochromatic interferogram of two sub-aperture system is analyzed based on physical principles, then the piston error detecting method is developed and clarified based on their linear relationship in the range of one wavelength. Furthermore, an innovative co-phasing detecting method based on grating dispersed interferogram with bandwidth light source is proposed, and its feasibility, detecting precision and dynamic range are analyzed in theory and studied in simulation. The results prove that with this method, the piston error between the two sub-apertures of the system can be soundly detected and its measuring error is less than 20 nm while the piston error is not more than 50 μm. In addition, the novel method solves the problems of 2π ambiguity and direction determination that might exist within some other detecting methods. Besides its millimeter level dynamic range, this new co-phasing detecting method provides a new way and an effective reference for in-depth research of co-phasing detecting techniques.

Electric field distribution, in the wavelength range 1053 nm and 0° high reflection coatings, with different truncated conical pits has been estimated by using the finite difference time domain method (FDTD). Results of simulations indicate that the smaller the angle between the pit’s edge and the normal line, the higher the damage threshold of the mitigation pit. In the experimental process, the dimension of this angle mainly depends on two factors, i.e. the influencing area of the focal spot and the depth of mitigation pits. Because the ratio between them is the angle’s tangent, decreasing the influencing area of the focal spot and increasing the depth of the machined area could yield a mitigation pit with a smaller angle. By optimizing the focal spot size, pulse energy, step size and the number of machining passes of femtosecond laser micromachining, a pit with an angle of 25° and a depth of 14 μm is obtained. The typical damage threshold of the mitigation pit is about 21 J/cm2, which is 2.3 times greater than the fluence-limited defect. Moreover, the laser damage testing results of 50 mitigation pits show that the mitigation process has a good repeatability. The correlation between the cone angle and the damage threshold is also examined, the simulations are in agreement with the experimental results. The ratio of the maximum intensification between 45° and 25° cone angles is ~2.5 and that of the damage threshold between the two angles is 0.5. At the same time, the relationship between the micromachining pulse width and the damage threshold is also estimated: if other process parameters are kept constant, a longer pulse length tends to produce lower laser-resistant mitigation pits. Compared to the result of 260 fs laser pulse, the truncated conical pit created by 6 ps laser pulse has a smaller depth, which implies that more thermal effect occurs during the miromachining process. However, cracks are not found around the pit. Thus, thermal damage is not the major reason for the decrease of damage threshold. Meanwhile, smaller depth also indicates that the pit has a large cone angle. According to the result of former FDTD simulation, the decrease of damage threshold is mainly caused by electric field enhancement in a pit with a large cone angle.

Magnetic reconnection (MR) is a universal physical process in plasma, in which the stored magnetic energy is converted into high-velocity flows and energetic particles. It is believed that MR plays an important role in many plasma phenomena such as solar fare, gamma-ray burst, fusion plasma instabilities, etc.. The process of MR has been studied in detail by dedicated magnetic-driven experiments. Here, we report the measurements of magnetic reconnection driven by Shenguang II lasers and Gekko XVII lasers. A collimated plasma jet is observed along the direction perpendicular to the reconnection plane with the optical probing. The present jet is very different from traditional magnetic reconnection outflows as known in the two-dimensional reconnection plane. In our experiment, by changing the delay of optical probing beam, we measure the temporal evolution of jet from 0.5 ns to 2.5 ns and its velocity around 400 km/s is deduced. Highcollimated jet is also confirmed by its strong X-ray radiation recorded by an X-ray pinhole camera. With the help of optical interferograms we calculate the jet configuration and its density distribution by using Abel inverting technique. A magnetic spectrometer with an energy range from hundred eV up to one MeV is installed in front of the jet, in the direction perpendicular to the reconnection plane, to measure the accelerated electrons. Two cases are considered for checking the acceleration of electrons. The results show that more accelerated electrons can be found in the reconnection case than in the case without reconnection. We propose that the formation and collimation of the plasma jet, and the electron energy spectrum may be possible directly influenced by the reconnection electric field, which is very important for understanding the energy conversion in the process of MR and establishment of the theoretical model. Finally the electron energy spectra of three different materials Al, Ta and Au are also shown in our work. The results indicate that the higher atomic number material can obtain a better signal-noise ratio, which provides some helpful references for our future work.

An experimental research platform is built on Shenguang II high power laser facility for obtaining the equation of state of liquid deuterium which has ability to control the temperature in a range of 12–300 K with an accuracy of ±0.03 K in 80 min. By optimizing the coating processing and cleaning the target, we solve the problems that the residual reflection is too high and serious frosting takes place on the window of the target at low temperature, then we obtain the experimental image with a good signal-to-noise ratio. By using the impedance matching method and velocity interferometer system for any reflector, experimental Hugoniot data of liquid deuterium are obtained at a pressure of about 60 GPa under the output condition of 3ω, 3 ns, 1200 J on Shenguang II high power laser, which agrees well with the other published data in the same pressure regime and provides a good foundation for the next experimental study of liquid deuterium equation in 100 GPa pressure regime.

Accurate measurements of the transmittance of large optical elements are essential to improve the energy density in inertial confinement fusion (ICF). The required complex transmittance of such optical elements used in ICF is obtained by computing the phase difference between the illuminating and transmitting fields using modulation coherent imaging (MCI). A phase plate designed as a modulator has a known transmission function in this technique. It presents a simple and quick method to measure the transmittance of large optical elements with irregular surface profiles by retrieving it from only two diffraction patterns recorded by a CCD camera. The complex transmittance of a continuous phase plate (CPP) with a large aperture used in ICF is measured experimentally, and the results are found to agree with the designed value.

High precision polystyrene equation of state data were measured using laser-driven shock waves with pressures from 180 GPa to 700 GPa. α quartz was used as standard material, the shock wave trajectory in quartz and polystyrene was measured using the Velocity Interferometer for Any Reflector (VISAR). Instantaneous shock velocity in quartz and polystyrene was obtained when the shock wave pass the interface. This provided ～1% precision in shock velocity measurements.

In this Letter, a single wavelength digital holographicmethod is proposed to achieve depth resolved imaging by recording a series of holograms in the reflection geometry with an illumination of constantly changing curvature. A proper algorithm is employed to selectively generate the images of the object at different depths, including the phase and the modulus information. Theoretical analysis is supported by a visible light experiment to illustrate the feasibility of the proposed method.

A polystyrene (CH)/resorcinol formaldehyde (RF)/CH tri-layer perturbation target for hydrodynamic instability experiments in inertial confinement fusion (ICF) was designed and fabricated and its features were discussed. The target was composed of a perturbed CH layer, a RF aerogel sheet and an unperturbed CH layer. The detailed fabrication method consisted of four steps. An aluminum alloy template with sinusoidal perturbation patterns was prepared by the single-point diamond turning technology; the CH layer was prepared via a simple method which called dip-coating method; the RF aerogel sheet was prepared by sol–gel and supercritical drying process; finally, a CH layer, the RF aerogel sheet and another CH layer were put on the perturbed aluminum alloy template and hot-pressed at 150 ℃ for 2 h to make these three layers adhered together without the use of adhesive and to transfer the perturbation patterns from the template to the CH layer. A scanning electron microscope (SEM) was used to investigate the microstructure of the RF aerogel sheet. Parameters of the target, such as perturbation wavelength (T) and perturbation amplitude (A), were characterized by QC-5000 tool microscope and alpha-step 500 surface profiler. The results showed that T and A of the target were about 55 and 3.88 lm respectively, the perturbation patterns transferred from the alloy template to the CH layer precisely. Thickness of the perturbed CH layer (H1), RF aerogel sheet (H2) and unperturbed CH layer (H3) and cross-section of the tri-layer target were characterized by QC-5000 tool microscope and SEM. H1, H2 and H3 were about 50, 300 and 20 lm respectively, the cross-sectional photographs of the target showed that the CH layer and the RF aerogel sheet adhered perfectly with each other. As this CH/RF/CH tri-layer target use the RF aerogel to simulate the DT ice of the ignition target capsule, the whole target very close to the actual ignition target capsule.

We report a high-energy and high-gain fiber regenerative amplifier for narrow-bandwidth nanosecond laser pulses that uses a Yb-doped photonic crystal fiber. The input pulse energy is 270 pJ for a 3.5 ns laser pulse with 0.3 nm (FWHM) bandwidth. At a pump laser power of 8.6 W at 974 nm, pulse energies up to 746 μJ with 1.2% (rms) energy stability are generated. To the best of our knowledge, this is the highest energy obtained in a fiber-based regenerative amplifier. A high-energy, nearly diffraction-limited, singlemode beam with a high gain of 64 dB shows promise for future application in the front ends of high-power laser facilities.

The scheme of prefocusing to focus sum frequency generation (SFG) without a lens is proposed and experimentally verified in this study. Noncollinear type-I noncritical phasematching SFG to generate a third-harmonic wave with large angular acceptance is presented. The principle of broad angular acceptance and the advantages of this PM configuration are also described in detail. External angular bandwidth of 7.33° for noncollinear SFG was measured in a 2 mm long KH2PO4 (KDP) crystal, which is in reasonably good agreement with the theoretical calculation. The mechanism of broadband SFG and the prefocusing scheme make it possible for the realization of convergent third-harmonic generation without involving a lens, which provides a promising way to avoid damage to optical components during the focusing of high-energy UV light in high-power laser facilities.

The evolution of hot-image formation in consideration of focusing lens effect is theoretically and numer-ically investigated. Through analysis of linear propagation theory with lens, it is shown that the locationof hot image in focusing systems can be predicated through definite functional relation to hot imageposition in non-focusing systems, on condition that the distance between the hot image and the lens isrelatively small. In addition through numerical calculation, specific variation characteristics of maximumintensity with the propagation distance representing hot-image formation process are presented, it isobtained that perturbing scatter size directly affects the location and corresponding peak intensity ofthe hot image. The lens influences the value of scatter size where minimum distance between hot-imageplane and focus lens is generated. Finally, the effects of phase and amplitude modulation of scatter on hotimage are also given. Results in this paper are of fair referenced value for controlling perturbing scatterand restraining the damage risk of optical components in focusing systems.

Air conditioning systems can lead to dynamic phase change in the laser beams of high-power laser facilities for the inertial confinement fusion, and this kind of phase change cannot be measured by most of the commonly employed Hartmann wavefront sensor or interferometry due to some uncontrollable factors, such as too large laser beam diameters and the limited space of the facility. It is demonstrated that this problem can be solved using a scheme based on modulation coherent imaging, and thus the influence of the air conditioning system on the performance of the high-power facility can be evaluated directly.

We successfully extend the standard Fibonacci zone plates with two on-axis foci to the generalized Fibonacci photon sieves (GFiPS) with multiple on-axis foci. We also propose the direct and inverse design methods based on the characteristic roots of the recursion relation of the generalized Fibonacci sequences. By switching the transparent and opaque zones, according to the generalized Fibonacci sequences, we not only realize adjustable multifocal distances but also fulfill the adjustable compression ratio of focal spots in different directions.

Pulse contrast is an important parameter for ultrafast pulses. It shall be 108 or higher in order to avoid effect from noise before main pulse. Diagnostics with cross-correlation can achieve high temporal resolution such as ~7fs. Cross-correlation has advantage in pulse contrast measurement than autocorrelation because it can distinguish noise before or after main pulse. High dynamic range is also essential in pulse contrast measurement. Cross-correlation signal from a single shot is converted into a signal series through fiber array, which can be analyzed by a set of a PMT and an oscilloscope. Noise from nonlinear crystal and scatter needs decrease to improve dynamic range. And pulse power is also discussed in pulse contrast experiments. Time delay τ is generated by travel stage in measurement for repetition pulses. Then energy instability will generate error in this measurement. In measurement for single shot pulse, time delay τ is generated by slant angle of beams. The scanning procession is completed with thousands parts of beam section within a single shot, and error will generated from no uniformity in near field. Performance test of pulse contrast measurement is introduced in subsequent sections. Temporal resolution is testified by self-calibration. Dynamic range is judged by a parallel flat. At last pulse contrast of petawatt laser is diagnosed by a single shot cross-correlator with high confidence. The ratio is 10-6 at 50ps before main pulse, and 10-4 at 10ps before main pulse.

Laser damage performance of large aperture optical components has been study under fourth harmonic of 1053nm Nd:glass laser irradiation (263nm).The threshold of optical components is very low under 263nm laser irradiation ,due to conversion of beam to higher energy photons of the quadrupled frequency (4ω), and is relative to material characteristic. A preliminary test of laser induced damage in fused silica (SiO2) and CaF2under 263nm laser is reported in this article. Thresholds of these two materials are obtained. Laser damage threshold of SiO2 is found about 2 J/cm2 by 1-on-1 method using pulsed 263nm laser, lower than CaF2 whose threshold.

We present a numerical model of internal modification in bulk borosilicate glass by high repetition rate picosecond laser pulses. We study free-electron dynamics, nonlinear energy deposition and thermal conduction. The optical absorptivity and modification regions both have good agreements with the experimental results. The smooth outer zone is the molten region and the inner-structure formation is caused by high-density free-electrons generated by thermal ionization. Excitation, relaxation and accumulation of free-electron density in the focal volume are analyzed using different pulse shapes and a double-pulse train. The deposited energy distribution and modification zone are controlled by pulse shaping.

Ultrashort pulse is important to exploring laser acceleration in many areas, such as fast ignition, advanced radiography capability. Petawatt laser should not only improve output energy on a single beam, but also combine multi-beams coherently. Diagnostics of temporal and phase synchronization is developed for coherent beam combination on a 10ps laser pulse. When two pulses are guided into the diagnostics, one goes through a temporal delay unit and a lens with a focal length 500mm, then arrives at detector unit, the other goes through a phase delay unit and the same lens, and then arrives at detector unit, too. First, temporal synchronization is adjusted by temporal delay unit and monitored by a crosscorrelation generator in the detector unit. Second, phase synchronization is adjusted by phase delay unit and monitored by a far field interferogram in the detector unit. In our design, temporal resolution is 6.7fs in temporal synchronization, and phase resolution is 0.007π in phase synchronization. Experiment has proved that this diagnostics is useful to realize synchronization between two ultrashort pulses both in temporal and in spatial.

According to the problem of gain medium cross section high illumination and non-uniformity, which is caused by the laser rod amplifier non-imaging pump style. Orthogonal test design method is used to research the effect of absorption coefficient, gain medium radius, number of xenon lamps, center distance of xenon lamps and gain medium on gain uniformity. The rod amplifier which is made up by the above four elements, its gain medium cross section illumination distribution is simulated by ASAP. The results show that center distance of xenon lamps and gain medium, number of xenon lamps have very little influence on the gain uniformity. When absorption coefficient equal to 5.1 cm-1, gain uniformity will reach the optimum. Under the circumstance of other three elements are equal, the bigger is the gain radius, the smaller slope reflection curve, and the better gain uniformity.

The deformation of KDP crystals caused by gravity and mounting force can induce the phase mismatch, resulting in the decrease of frequency conversion efficiency. Loading strips are used to reduce the distortion in some existing methods, but it is difficult to fabricate. In order to improve the surface shapes of KDP crystals, small loading plates are used instead of loading strips. The mounting configuration is analyzed by finite element methods (FEM) and the position of the loading plates is optimized by adaptive single-objective algorithm. The results show the effectiveness of the mounting configuration in reducing the gravitational sag of KDP crystals.

A kind of diffractive optical elements (DOE) with star-ring topological structure is proposed and their focusing and imaging properties are studied in detail. The so-called star-ring topological structure denotes that a large number of pinholes distributed in many specific zone orbits. In two dimensional plane, this structure can be constructed by two constrains, one is a mapping function, which yields total potential zone orbits, corresponding to the optical path difference (OPD); the other is a switching sequence based on the given encoded seed elements and recursion relation to operate the valid zone orbits. The focusing and imaging properties of DOE with star-ring topological structure are only determined by the aperiodic sequence, and not relevant to the concrete geometry structure. In this way, we can not only complete the traditional symmetrical DOE, such as circular Dammam grating, Fresnel zone plates, photon sieves, and their derivatives, but also construct asymmetrical elements with anisotropic diffraction pattern. Similarly, free-form surface or three dimensional DOE with star-ring topological structure can be constructed by the same method proposed. In consequence of smaller size, lighter weight, more flexible design, these elements may allow for some new applications in micro and nanphotonics.

Large-aperture ultrashort ultrahigh intensity laser systems are able to achieve unprecedented super-high peak power. However, output power from a single laser channel is not high enough for some important applications and it is difficult to improve output power from a single laser channel significantly in the near future. Coherent beam combining is a promising method which combines many laser channels to obtain much higher peak power than a single channel. In this work, phase effects of coherent beam combining for large-aperture ultrashort laser systems are investigated theoretically. A series of numerical simulations are presented to obtain the requirements of spatial phase for specific goals and the changing trends of requirements for different pulse durations and number of channels. The influence of wavefront distortion on coherent beam combining is also discussed. Some advice is proposed for improving the performance of combining. In total, this work could help to design a practical large-aperture ultrashort ultrahigh intensity laser system in the future.

With the increasing number of laser beams, the main difficulty in arranging beam guiding systems (BGSs) involves determining the corresponding relationships between the output and input ports to realize the identified light path length of all beams. Given the basic constraints of geometric arrangement, a BGS model is established, and a base-line algorithm is proposed to address the difficulty mentioned above. Boundary conditions of target area and target chamber are discussed to increase the number of laser beams, and a maximum value exists for a specific target area. Finally, the compatibility of a cylindrical hohlraum target chamber with a spherical hohlraum is analyzed, and a moveable final optics assembly is proposed to execute the switch between the two different targets.

A new method is proposed to deduce the temporal resolution of a single-shot autocorrelator. A resolution test pattern is installed in one arm of the autocorrelator to add streaks on the beam cross section. Therefore, the autocorrelation signal is modulated when the streaked beam arrives at an autocorrelation crystal. Given the relationship between streak width and temporal delay in an autocorrelator, the temporal resolution is determined by the noncollinear angle, the streak’s width of the resolution test pattern, and the autocorrelation signal. Comparison experiments show that the proposed and conventional calibration schemes yield temporal resolutions of 65.6 and 67.8 fs∕pixel, respectively, with a relative error of 3.3%. An advantage of this method is that fine temporal resolution (65.6 fs∕pixel) is achievable on a short pulse (10 ps) despite the lack of a femtosecond pulse.