Light propagation through large laser systems

Simmons, W. W.; Hunt, John T.; Warren, W. E.

doi:10.1109/jqe.1981.1071337

Cited by 86 publications

(19 citation statements)

References 34 publications

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“…According to physics formulas of the low-pass filtering and relay imaging in spatial filters [11], the exit field passing through the spatial filter is related to that at the entrance by the propagation algorithm,…”

Section:  mentioning

confidence: 99%

Evolution of low-frequency noise passing through a spatial filter in a high power laser system

Sun

Liu

Zhang

et al. 2011

Sci. China Phys. Mech. Astron.

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The theoretical model of spatial noise passing through a spatial filter is established in high power laser system under the small signal approximation. The transmission characteristic for a noise signal passing through spatial filters with different magnifications is analyzed by numerical simulation, according to the actual structure of the high power laser system. The results show that the spatial modulation period of low-frequency noise getting through the pinhole will be proportional to the magnification of the spatial filter. When the magnification is less than 1, the safe low-frequency noise will be extruded into the high-frequency region, which is the fast increasing part, and finally develops into the most dangerous part which can damage the optical devices. The conclusion of this research improves the relay imaging theory of a spatial filter and provides an important theoretical basis for a general design of high power laser systems.high power laser, spatial filter, spatial modulation frequency, modulation contrast ratio PACS: 42.65.Jx, 41.85.Ct, 42.30.Kq

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Section:  mentioning

confidence: 99%

Evolution of low-frequency noise passing through a spatial filter in a high power laser system

Sun

Liu

Zhang

et al. 2011

Sci. China Phys. Mech. Astron.

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“…4 This control is based on the understanding that: 1. diffraction increases amplitude variations as the beam moves away from its near field, and 2. nonlinear driven amplitude variations grow as the beam propagates along its path. As shown in Fig.…”

Section: Architectural Evolution Of Icf Laser Beamline Designsmentioning

confidence: 99%

National Ignition Facility wavefront requirements and optical architecture

et al. 2004

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With the first four of its eventual 192 beams now executing shots and generating more than 100 kJ of laser energy at its primary wavelength of 1.06 m, the National Ignition Facility (NIF) at the Lawrence Livermore National Laboratory is already the world's largest and most energetic laser. The optical system performance requirements that are in place for NIF are derived from the goals of the missions it is designed to serve. These missions include inertial confinement fusion (ICF) research and the study of matter at extreme energy densities and pressures. These mission requirements have led to a design strategy for achieving high-quality focusable energy and power from the laser and to specifications on optics that are important for an ICF laser. The design of NIF utilizes a multipass architecture with a single large amplifier type that provides high gain, high extraction efficiency, and high packing density. We have taken a systems engineering approach to the practical implementation of this design that specifies the wavefront parameters of individual optics to achieve the desired cumulative performance of the laser beamline. This paper provides a detailed look at the causes and effects of performance degradation in large laser systems and how NIF has been designed to overcome these effects. We also present results of spot size performance measurements that have validated many of the early design decisions that have been incorporated in the NIF laser architecture.The optical quality or wavefront specifications for the laser slabs, crystals, windows, lenses, and mirrors that make up the National Ignition Facility ͑NIF͒ beamlines were established by flowdown analysis of those that were needed for these components to meet the primary criteria and functional requirements for the NIF laser system. In this work we summarize the NIF primary system criteria that are influenced by the wavefront quality of a beamline, and then describe how the beamline architecture and specifications for individual optical components have made it possible for NIF to meet its system criteria.The national motive for building the NIF laser centers around providing a laser driver for three missions of national purpose:• inertial confinement fusion ͑ICF͒ • the high-energy-density study of materials of interest to the stockpile stewardship program • the study of materials under very high temperatures and pressures of interest to the scientific community, particularly the astrophysical community.Of these user groups, the one that was most active in establishing the original specifications for NIF was the ICF community; their emphasis for the initial embodiment of NIF was for indirect drive ICF. For this mission, laser light enters a hohlraum through two laser entrance holes ͑LEH͒ to irradiate the walls of the hohlraum, subsequently generating x-rays that drive the implosion of a capsule centrally located within the hohlraum. 1 Thus, the primary wavefront requirement for NIF became its ability to provide focusable energy and power into the laser ...

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“…This is due to the non-linear phase retardance that occurs in the material at high intensity. 4,5,6 The magnitude of the phase retardance is characterized by the "B integral" given by the expression:…”

Section: Thickmentioning

confidence: 99%

“…It is obvious from eq. 2 that the critical flaw size for failure varies as (t/d) 4 . In other words slightly increasing the thickness of a given window dramatically reduces the chance for failure.…”

Section: Some General Principles Governing Fracture In Glass Platesmentioning

confidence: 99%

<title>Laser-induced damage and fracture in fused silica vacuum windows</title>

et al. 1997

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Laser induced damage, that initiates catastrophic fracture, has been observed in large (up to 61-cm diameter), fused silica lenses that also serve as vacuum barriers in high-fluence positions on the Nova and Beamlet lasers. In nearly all cases damage occurs on the vacuum (tensile) side of the lens. The damage can lead to catastrophic crack growth if the flaw (damage) size exceeds the critical flaw size for SiO 2 . If the elastic stored energy in the lens is high enough, the lens will fracture into many pieces resulting in an implosion. The consequences of such an implosion can be severe, particularly for large vacuum systems. Three parameters control the degree of fracture in the vacuum barrier window: 1) the elastic stored energy (i.e. tensile stress) 2) the ratio of the window thickness to flaw depth and 3) secondary crack propagation. Fracture experiments have been carried out on 15-cm diameter fused silica windows that contain surface flaws caused by laser damage. The results of these experiments, combined with data from window failures on Beamlet and Nova have been used to develop design criteria for a "fail-safe" lens (that is, a lens that may catastrophically fracture but will not implode). Specifically the window must be made thick enough such that the peak tensile stress is less than 500 psi (3.4 MPa) and the corresponding ratio of the thickness to critical flaw size is less that 6. Under these conditions a properly mounted window, upon failure, will break into only two pieces and will not implode. One caveat to these design criteria is that the air leak through the window fracture and into the vacuum must be rapid enough too reduce the load on the window before secondary crack growth occurs. Finite element stress calculations of a window before and immediately following fracture into two pieces show that the elastic stored energy is redistributed if the fragments "lock" in place and thereby bridge the opening. In such cases, the peak stresses at the flaw site can increase leading to further (i.e. secondary) crack growth.

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Light propagation through large laser systems

Cited by 86 publications

References 34 publications

Evolution of low-frequency noise passing through a spatial filter in a high power laser system

Evolution of low-frequency noise passing through a spatial filter in a high power laser system

National Ignition Facility wavefront requirements and optical architecture

<title>Laser-induced damage and fracture in fused silica vacuum windows</title>

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