Applied Optics, Vol. 24, Issue 4, pp. 538-543 (1985)
ABSTRACT
This paper shows that a fundamental Gaussian beam propagating in a lenslike medium with cylindrical symmetry can be generated by the rotation about its axis of a skew ray which obeys the laws of geometrical optics. A complex representation: X(z) = ξ(z) + jη(z), where ξ(z) and η(z) are the projections of the skew ray on two perpendicular meridional planes, is discussed. It is found that the beam radius is equal to the modulus of X(z) and the on-axis phase to the phase of X(z). Using this representation, we derive a general expression for the on-axis phase shift ΔΦ experienced by a beam with an input complex beam parameter q through an optical system whose ray matrix is [ACBD]:ΔΦ=phase of(A+B/q). When the beam is matched to the optical system (output q = q), ΔΦ can be written cos–1(A + D)/2. This representation also provides a useful beam tracing method which is demonstrated and a simple interpretation for the known representation of Gaussian modes by ray packets.
We have calculated the noise-enhancement factor of a semi-conductor laser amplifier with a very thin active region. This (somewhat academic) model exhibits large Petermann’s K-factors. However, the calculated noise-enhancement factor K’is only about half the K-value. The reason for the discrepancy is that in evaluating K’ the radiation modes of the guiding strcture have been taken into account. Similar conclusions have been reached for realistic laser models. These theorical considerations show that gain-guided laser amplifiers are not noisy as was originally thought.
I show that a theoretical expression for the dispersion (…) of tubular modes in dispersive multimode square-law fibers coincides with the wave-optics result.
Optical and Quantum Electronics 16 (1984) 125-130, 1984
ABSTRACT
The complex ray representation of Gaussian beams proposed by the author in 1968 is applied to the propagation of pulses with Gaussian envelope. Linear propagation in uniform time-invariant waveguides is first considered. Next, closed-form solition solutions are obtained for a special kind of nonlinearity.
Jacques Arnaud, Laurent Chusseau, Fabrice Philippe
Electronics Letters, Volume 19, Issue 19, 15 September 1983, p. 798 – 800
ABSTRACT
We give an argument suggesting that spontaneous emission in gain-guided laser amplifiers is enhanced by a factor much smaller than the K-factor previously calculated. This is because the fundamental mode content of the spontaneous emission field should be calculated in the sense of the Hermitian rather than direct product at the laser output.
Optical waveguides sciences, Proceedings of the international symposium, june 20-23, 1983, pp. 17-25
ABSTRACT
In this paper, we have no attempt to present some results which, basically, have not been known before. What we wish to emphasize is the analogy that exists between space and time concepts, pulse spreading in dispersive media being analogous to beam diffraction.
Journal of Optical Society of America, vol 73, page 661, may 1983
ABSTRACT
The effect of periodic axis deformations on propagation in multimode optical fibers with single-mode excitation are investigated numerically and experimentally. The numerical study, based on ray theory, deals with helical rays in the presence of sinusoidal axis deformations for various shapes of index profile. The corresponding experimental observations and results, carried out on tubular modes, confirm the existence of resonance effects between the halical ray period and the fiber axis deformation. This technique permits the observation od mode-to-mode power transfer and provides a sensitive tool to investigate the mode-coupling mechanism in optical fibers.
Extrait Annales des Télécommunications, tome 38, n° 1-2, janvier/février 1983
ABSTRACT
Des problèmes théoriques relatifs aux télécommunications optiques, aux capteurs, lasers et dispositifs d’imagerie ont été discutés de façon informelle par quarnte scientifiques au Colloque international sur la théorie des guides optiques. La réunion s’est tenue juste avant la Conférence européenne sur les communications optiques (ECOC, Cannes, sept. 1982) au Centre inter-régional d’enseignement sur les télécommunications (CIRET) à La Londe. Un rapport concis est présenté.