In an inertial confinement fusion (ICF) system, wave-front aberrations existed in laser beam will enlarge the focal spot
size and decrease power density at the target. Fortunately, an adaptive optical system (AO) could be employed in ICF
system to correct the beam aberrations. As a powerful wave-front detector, Hartmann-Shack (H-S) sensor is often
utilized as a wave-front sensor in AO. However, H-S sensor can not detect the aberrations after the sampling location. A
new method is presented to measure the aberrations of entire ICF beam path in this paper. Based on the AO, a CCD is
installed in the target chamber to detect the focal spot distribution. The deformable mirror's (DM) is yielded to different
surface shapes; the extra different aberrations are modulated and added to ICF beam path, and then create their
corresponding focal spots. The extra aberrations and the corresponding focal spots intensity could be recorded
simultaneously by H-S sensor and CCD respectively. An amendatory phase-retrieval algorithm which is introduced can
reconstruct the aberrations of entire ICF beam path from the pairs of extra aberrations and their corresponding focal spots
intensity. The numerical simulation show that the AO can correct the aberrations of entire beam path of ICF successfully
based on this method.
In 1980, the first laboratory on Adaptive Optics in China was established in Institute of Optics and Electronics, Chinese Academy of Sciences. Several adaptive optical systems had been set up and applied in Inertial Confinement Fusion (ICF) and retinal high-resolution imaging. In 1985, the first adaptive optical system for ICF equipment was set up in the world. Another 45 element adaptive optical system was first built for correcting the static and dynamic wavefront aberrations existed in the large-aperture Nd: glass laser for inertial confinement fusion in 2001. Two set adaptive optical system with 19-element and 37-element deformable mirror had been developed for human retina imaging in 2000 and 2002 respectively. In this paper, the function and performance of these adaptive optical systems are described and the experiment results are presented.
Light waves passing through the turbulent flow are aberrated by refractive index fluctuations in the flow. Refractive index fluctuations arise from density fluctuations driven by temperature and pressure variations in turbulent flow. Hartmann-Shack wavefront sensor can directly sense these aberrations and also can reconstruct the 3-dimensional structure of the refractive index distribution in a turbulent flow field with tomographic reconstruction technique. A novel method for measuring the 3-dimensional structure of the refractive index distribution in a turbulent flow field combining Hartmann-Shack wavefront sensor with tomographic reconstruction is proposed in this paper. Hartmann-Shack wavefront sensor is used for measurement of an optical wave front after passing through a flow field and the refractive index distribution is reconstructed by computed tomography technique. The principle of the tomographic reconstruction of the flow field based on the Hartmann-Shack wavefront sensor is described briefly. The static symmetric and dynamic asymmetric experimental results are presented. The experimental results indicate that Hartmann-Shack wave-front sensor combining with tomographic reconstruction technique has a potential application for material and flow field investigation regions.
Hartmann-Shack wavefront sensors are widely used in adaptive optical systems. It can measure the spatial-temporal errors of dynamic wavefront. Not only the phase but also the amplitude of a wavefront can be measured. Unlike an interferometer, it is not necessary to have a real-time reference beam, so it can work in a disturbing environment. Besides used in adaptive optics systems, Hartmann-Shack wavefront sensors also become a powerful tool in two fields: light beam diagnosis and optical testing of optical components and systems. We have developed a serial of Hartmann-Shack wavefront sensors used in these two fields. In this presentation, various applications of Hartmann-Shack wavefront sensors in these fields will be reported.
A novel PSD-based Hartmann-Shack wavefront sensor (HSWFS) prototype has been developed, which employs a 4X4 PSD array as the detector to measure the displacements of the sub-aperture spots. Compared with the conventional CCD-based HSWFS, it can operate at very high sampling rate, and it only has very short readout delay time. Our system can measure wavefront at frame rate up to 5KHz, and the detected wavefront error is less than λ/50 (λ=632.8nm). In this paper the experimental results are given. The measurement error of the PSD-based HSWFS for a given aberrated plate is compared with the measure result of the Zygo interferometer.
An adaptive optical system with a 45-channel deformable mirror and a Shack-Hartmann wavefront sensor with 10 x 10 sub-apertures was built for correcting the static and dynamic wavefront aberrations existed in the large-aperture Nd: glass laser for inertial confinement fusion. This paper describes the function and performance of the adaptive optical system. The latest experiment results on the ICF laser system are presented.
A novel PSD-based Hartmann-Shack wavefront sensor(HSWFS) prototype has been developed. Compared with the conventional CCD-based HSWFS, it can operate at very high sampling rate, and it only has very short readout delaytime. In this paper, the PSD-based HSWFS is described in details, and the performances of the PSD-based HSWFS and the CCD-based HSWFS are compared.
Before the design of adaptive optical system for the aberration correction in the proposed new generation laser driving Inertial Confinement Fusion (ICF) system, the spatial and temporal characteristics of aberration of this system should be studied and understood deeply. A single beam principle prototype of this ICF system has been built. The Shack-Hartmann wave-front sensors have been designed and constructed. Wave-front aberrations of this prototype are measured and studied.
An adaptive optical system has been built for improving optical beam quality in a new inertial confinement fusion (ICF) system. This system is designed to compensate the static and dynamic wavefront errors in the laser generator and amplifier by pre-compensation manner, which includes a 45-channel deformable mirror, two Shack-Hartmann wavefront sensors with 10x10 sub-apertures, a 45-channel high voltage amplifier and a wavefront control computer. Preliminary principle experiment has been done and the experimental results are reported.
Known the wave-fronts of the ICF amplifiers is very important for improving the design and adjustment of the amplifiers and designing the adaptive optical system that can be used to shape the beam or clean it up. Because the pulse of ICF laser is ns scale, the wave-front can not be measured with common methods. In this paper, a method with a Hartmann-Shack wave- front sensor based on the progressive scan CCD camera is introduced. The test results show that this method is effective.