Complete modal decomposition for optical fibers using CGH-based correlation filters

Abstract

The description of optical fields in terms of their eigenmodes is an intuitive approach for beam characterization. However, there is a lack of unambiguous, pure experimental methods in contrast to numerical phase-retrieval routines, mainly because of the difficulty to characterize the phase structure properly, e.g. if it contains singularities. This paper presents novel results for the complete modal decomposition of optical fields by using computer-generated holographic filters. The suitability of this method is proven by reconstructing various fields emerging from a weakly multi-mode fiber (V approximately 5) with arbitrary mode contents. Advantages of this approach are its mathematical uniqueness and its experimental simplicity. The method constitutes a promising technique for real-time beam characterization, even for singular beam profiles.

Gas-assisted laser cutting of medium-section metals using spherically aberrated beams

“…68 These facts generated a certain scepticism as to the versatility of the M 2 approach, expressed even by the author of this concept in his subsequent papers. 69 Qualitatively, it is evident that any M 2 degradation 60 as well as the dramatically rarely used Strehl ratio, 70,71 the overlapping integral, 71 and the V-parameter 66 witness some LID distortion. However, knowing the actual LID shape in an interaction region is desired.…”

“…65 Determination of 4σ -size of noticeably non-Gaussian beams becomes too time consuming. Express techniques 66,67 are not regularly applied. Introducing M 2 into the Gaussian beam equations suggests the caustic symmetry 37,62,64 that is never asserted for an aberrated beam.…”

Mathematical model of completely optical system for detection of mode propagation parameters in an optical fiber with few-mode operation for adaptive compensation of mode coupling

“…где ψ[p,q] -комплексные коэффициенты, опреде-ляющие распределение мод и выражаемые как [9]: С точки зрения квантового подхода каждый фотон переносит OAM, выражаемый как pħ [21], так что ка-ждая LP-мода переносит OAM, пропорциональный индексу p. Если мы рассмотрим только набор из N = (2Λ + 1) мод, различающихся индексами p (индекс q будем считать постоянным, а коэффициенты ψ[q] равными единице), тогда линейная суперпозиция LP-мод, подаваемых на вход в волокно, может быть за-писана как:…”

5 × 5 25 Gbit/s WDM-MDM

“…An elegant approach that has attracted significant attention is mode division multiplexing (MDM) [19], realized by combining or separating modes at the multiplexer and demultiplexer for transmitting independent data streams. Recent MDM demonstrations employ spatial light modulators [5,21,22], fiber gratings [23][24][25][26][27][28], digital signal processing algorithms [29][30][31], modal decomposition algorithms [32][33][34], adaptive optics [7,[35][36][37][38] and photonic crystal fiber [39].…”