Effect of field regeneration on the TEM_00 transmission characteristics of a circular-section waveguide

Abstract

The transmission of a 10.6-microm TEM(00) beam through a hollow circular-cross-section waveguide is modeled in terms of the excitation and propagation of the two lowest-order circularly symmetric EH(1n) modes. At points along the guide axis where the are in phase the TEM(00) input field is shown to be regenerated, but midway between these points, transverse-mode profiles that have a doughnut shape are produced. It is proposed that these dramatic field variations should cause variations in the effective attenuation coefficient along the length of the waveguide. The first direct experimental measurements to our knowledge of the guide-length-dependent attenuation characteristics of a 1.0-mm-bore hollow silica waveguide support this hypothesis by revealing a strong periodic component in addition to the anticipated exponential decay.

Hollow-waveguide delivery systems for high-power, industrial CO_2 lasers

“…For optimal coupling of a Gaussian input beam, the spot size should be focused to a diameter that is 0.64 times the waveguide bore diameter. 18,20,21 However, with a multimode beam it is impossible to achieve the optimum coupling. Therefore we compromised on a focusing lens with a focal length f of 254 mm 110.0 in.2.…”

Quantum cascade laser light propagation through hollow silica waveguides

“…The value of the coupling coefficient is dependent on the spatial distribution of the light field in the image plane of the coupling lens and the mode profile of the waveguide. This can be computed from the overlap integral and has been done previously for single-mode fibres [24], and for hollow waveguides [12,25,26], where E beam is the Gaussian spatial laser beam profile and E waveguide is the spatial profile of the HE 1m modes of the waveguide, given by where 0 < r < a and J 0 represents the zero-order Bessel function of the first kind. The focused beam waist ω is related to the f-number of the coupling lens by…”

Output characteristic of a gain guided, index anti-guided fiber amplifier under the condition of gain saturation

“…To understand the propagation characteristic of a Gaussian beam inside a GG + IAG fiber, we decompose the Gaussian input field in terms of the fiber modes of EH 1m by a Bessel-Fourier series [10].…”