Mohamed Fadhali

Mode matching for efficient laser diode to single mode fiber coupling

This paper presents some analysis for the matching between the elliptical mode field of 1550nm high power laser diode with the circular mode field of the single mode fiber in order to obtain high coupling efficiency with relaxed misalignment tolerances. Three coupling schemes namely Butt, single ball lens and double ball lenses coupling schemes have been employed in pigtailing the butterfly laser diode module using laser welding technique with dual beams from Nd:YAG laser welding system for the attachment of coupling components. The process of fiber attachment to laser diode and welding of various coupling components, such as lens holders, fiber ferrule and welding clips have been performed in what is so called active alignment process, where the system continues measuring the coupled power during the process of coupling and welding of coupling components in their holder to each other and to the main substrate. It has been found that double ball lenses coupling scheme is efficient and more effective for mode matching of highly elliptical (large divergence ratio) laser diode mode field with the circular mode field of a single mode fiber, whereas for small divergence ratios the single ball lens is adequate.

Simplified coupling power model for fibers fusion

Fiber coupler fabrication used for an optical waveguide requires lossless power for an optimal application. The previous research coupled fibers were successfully fabricated by injecting hydrogen flow at 1 bar and fused slightly by unstable torch flame in the range of 800–1350°C. Optical parameters may vary significantly over wide range physical properties. Coupling coefficient and refractive index are estimated from the experimental result of the coupling ratio distribution from 1% to 75%. The change of geometrical fiber affects the normalized frequency V even for single mode fibers. V is derived and some parametric variations are performed on the left and right hand side of the coupling region. A partial power is modelled and derived using V, normalized lateral phase constant u, and normalized lateral attenuation constant, w through the second kind of modified Bessel function of the l order, which obeys the normal mode and normalized propagation constant b. Total power is maintained constant in order to comply with the energy conservation law. The power is integrated through V, u, and w over the pulling length of 7500 µm for 1-D. The core radius of a fiber significantly affects V and power partially at coupling region rather than wavelength and refractive index of core and cladding. This model has power phenomena in transmission and reflection for an optical switch and tunable filter.

Breakdown voltage investigation of fusion SiO2 optical coupler switch using Pockel effect model

This paper describes a new model for the breakdown voltage of SiO2 fiber coupler using the Pockel effect and empirical equation. The model is evaluated by using the coupling coefficient and the changes in the refractive index. We found that the breakdown voltage is in the order of 102 volt correspond to coupling coefficient by the order of mm-1. Increasing the value of coupling coefficient between the electrodes leads to a reduction in the breakdown voltage.

Nonlinear parametric studies of photon in a Fiber Bragg Grating

This paper describes the effect of alpha, α and gamma,γ changes to the motion of photon in a Fiber Bragg Grating. The study has been successfully performed under Bragg resonance condition where the initial frequency of the light,W0 has the same value with the Bragg frequency, WB. The Stokes parameter is chosen to provide important information about the total energy and energy difference between the forward and backward propagating modes. The motion of a particle moving is shown with the classic anharmonic potential where the beta, β is set to zero due to power conservation along the grating structures.

The comparative study of optical fiber coupling scheme in pigtailing of semiconductor optical amplifiers

In this paper we present analysis on three different coupling systems, i.e., butt, single ball lens, and two ball lenses between the tips of two coupled single mode fiber in semiconductor optical amplifier (SOA) module. The coupling components inside the module can be aligned in an active alignment process and attached by means of dual beam from an Nd: YAG laser welding system. The tips of the coupled fiber are ferruled inside metallic tubes to enable the attachment to the substrates through saddle-shaped welding clips. Investigations of the variations of coupling efficiency with the with working distance for the three schemes showed that two ball lenses is more efficient with coupling efficiency of 75% followed by single ball lens at 55% and butt coupling mode at 20% maximum. In addition dual ball lens configuration have shown to have better longitudinal tolerant even with an elliptical beam profile from the source fiber. This is however not the case in single ball lens and butt coupling scheme. We also observe however the optimum separation between the two lenses at in the range between 0.35 mm - 0.45 mm. This is to ensure the coupling efficiency is the highest possible within the acceptable tolerant misalignments.

Laser welding characterization of kovar and stainless steel alloys as suitable materials for components of photonic devices packaging

The weldability of Kovar and stainless steel alloys by Nd:YAG laser beam is studied through changing of some laser beam parameters. It has been found that there is a suitable interaction of the pulsed laser beam of low power laser pulse with both the two alloys. The change of thermophysical properties with absorbed energy from the laser pulse is discussed in this paper which reports the suitability of both Kovar and stainless steel 304 as the base materials for photonic devices packaging. We used laser weld system (LW4000S from Newport) which employs Nd:YAG laser system with two simultaneous beams output for packaging 980 nm high power laser module. Results of changing both laser spot weld width and penetration depth with changing both the pulse peak power density, pulse energy and pulse duration show that there are good linear relationships between laser pulse energy or peak power density and pulse duration with laser spot weld dimensions( both laser spot weld width and penetration depth). Therefore we c...