摘要:

A travelling-wave optical parametric amplifier (OPA) is treated, and basic theoretical results are summarized. An OPA connected to KDP crystals pumped by second harmonic pulses (λ= 0·532 μm, τ ≃ 20 ps) from a Nd: YAG laser was studied. The dependence of temporal and spectral parametric pulse properties on the conversion rate (gain saturation) was investigated. Nearly bandwidth-limited pulses (τ Δv˜ 0·6) were obtained at low energy conversion. A pulse reduction to 8 ps was measured in this case. At higher conversion ≳ 10 per cent, the stability of the output energy was higher. However, the pulse quality decreased considerably.

ISSN:0030-3909    

DOI:10.1080/713820777

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Bistable operation of an initially detuned Fabry-Perot etalon with a spatially varying transverse input is studied numerically. Non-linear medium propagation effects are accounted for explicitly. Fast Fourier transforms are used to treat beam diffraction, providing a computationally efficient numerical algorithm. Steady state bistable loops are computed for a Fresnel number close to unity, under both self-focusing and defocusing conditions. Beam diffraction causes earlier switch-on in the defocusing case.

ISSN:0030-3909    

DOI:10.1080/713820780

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The quantum statistical properties of Brillouin scattering of intense laser light are derived including the coupling of Stokes, anti-Stokes and phonon modes, if the anti-Stokes interaction prevails. Making use of the coherent-state technique, the Heisenberg equations of this process are solved neglecting the loss mechanism, and the normal quantum characteristic function and the normal generating function are derived. The time dependences of the photon distribution and its factorial moments are demonstrated if the phonon, Stokes and anti-Stokes modes are initially in a coherent state and periodical anti-bunching of the field is found when the phases of the incident fields fulfil certain phase conditions; the field can also return to the coherent state again.

ISSN:0030-3909    

DOI:10.1080/713820786

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The aim of the paper is to put forward an iterative procedure for solving a class of ill-posed inverse optical problems, namely those that are expressed by a convolution-type Fredholm equation of the first kind. This class includes the problem of recovering a signal distorted by a system and in particular the object restoration problem. The method proposed is based on changing the operator, i.e. on converting the Fredholm equation of the first kind into one of second kind. An iterative algorithm for implementing the method is suggested and compared with other iterative procedures.

ISSN:0030-3909    

DOI:10.1080/713820781

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The effect of polydispersity on the total integrated intensity and spectral density of light scattered by linear polymers in dilute solution is studied. Use is made of the chain model with nearest- and next-nearest-neighbour linear interactions. The length distribution is chosen to be that of Schulz. The analysis proceeds via normal mode decomposition, and the centre of mass contribution to the spectral density—as well as that of the normal modes, with and without mixing—becomes visible. The influence of polydispersity and elastic constants is significantly manifested in the normal mode contributions, and the spectral density curves of the polydisperse system are narrower than those of the monodisperse case.

ISSN:0030-3909    

DOI:10.1080/713820784

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The light transmission of an astronomical spectrograph could be increased if the collimator were eliminated, the aberrations that arise at the diffraction grating in a diverging beam from the slit being corrected in the spectrograph camera. This possibility is explored, and designs given for two such systems suitable for low-dispersion, faint-object spectroscopy.

ISSN:0030-3909    

DOI:10.1080/713820789

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor