Coherent Flat-topped Beam Research Articles

Paraxial propagation of partially coherent flat-topped beam

The propagation of flat-topped beam passing through a paraxial optical ABCD system is extended to partially coherent case and has been studied in detail. Based on Wigner distribution function (WDF), the irradiance distribution of partially coherent flat-topped beam is derived. Furthermore, two propagation parameters, such as M2-factor and Power in Bucket (PIB) are illustrated analytically and numerically.

Beam propagation factor of partially coherent beams in gain or absorbing media

The definition of second-order intensity moments in the spatial domain and spatial frequency domain has been generalized for the case that the linear gain or absorbing media are included, where the wave number is generally complex. The formula for beam propagation M 2-factor of partially coherent beams in linear gain or absorbing media has been given. The partially coherent flat-topped Schell-model beam is taken as an example. The closed-form expression for the beam propagation M 2-factor of partially coherent flat-topped beam in gain or absorbing media has been derived. The changes of the M 2-factor in media have been discussed with numerical examples. It can be shown that the M 2-factor of flat-topped Schell-model beams in gain or absorbing media depends on the coherent parameter β, the coherent length σ 0 , the beam order M, the propagation distance B, the imaginary part of the wave number K i, as well as the real part of the wave number K r.

Partially coherent flat-topped beam and its propagation.

A partially coherent beam with flat-topped profile is proposed. The cross-spectral density of this beam can be expressed as a finite series of the cross-spectral density of partially coherent Gaussian-Schell-model beams with different parameters. Analytical propagation formulas for partially coherent flat-topped beams are derived through aligned and misaligned optical systems. The propagation property of partially coherent flat-topped beams in free space is illustrated numerically. The fractional Fourier transform of partially coherent fiat-topped beams is also studied. Our method provides a convenient way to describe partially coherent flat-topped beams and treat their propagation and transformation.

Modal decomposition of partially coherent flat-topped beams produced by multimode lasers

We present a simple mathematical model giving a possible description of a partially coherent light beam exhibiting a flat-topped transverse intensity profile. Such a model allows us to deduce the modal distribution inside a multimode stable optical cavity, assuming that the modes are of the Hermite-Gauss type. The analytical expression used to represent flat-topped profiles is of the flattened Gaussian type and leads to an exact, closed-form expression for the M(2) factor of the output beam. An analogous procedure could be used to treat the general problem of deducing the modal distribution inside a laser cavity starting from intensity measurements of the output beam.

Cultivation of algae in heavy water

The focal shift and focal switch of phase-lock partially coherent flat-topped (PCFT) array beams passing through a lens system with aperture is studied in detail. It is shown that there is a focal shift for mention beam propagating through aligned optical system and the amount of the focal shift depend on optical system and beam characteristics. In addition, a new phenomenon called focal switch occurs for misaligned optical system, i.e. the focal shift experiences a sudden transition as the aligned optical system turns to misalign one. It is shown that, the necessary conditions for the focal switch to take place are also investigated.