Study On Optical Properties Of Rare Earth Doped Gain Applications

As a new approach of achieving large mode area and stable signal mode, whichis essential in high power fiber lasers and amplifiers that has shown wide use inindustry manufacturing, material processing and national defence, gain-guidedindex-antiguided （GG-IAG） fiber has attracted lots of attentions since this conceptionwas proposed.In the first part of this work, we focused on properties of this novel configurationand studied the performance of GG-IAG fiber amplifiers.By comparing several different technologys to achieve high power fiberlasers/amplifiers, attention was focused on GG-IAG fiber, then the basic principles ofthis fiber was illustrated and the developments on this fiber was reviewed.The absorption characteristics are the important parameters for fibers, it showsthe ability how much pumped light is absorbed by the doped fiber core. In lasermanufacturing, the absorption characteristics are very desired for both fiber laser andamplifier design and optimization, also it sheds light on fiber design. The absorptioncharacteristics of this novel double-clad Gain-guided and index-antiguided （GG-IAG）fiber are investigated with3D-ray-trace method. And the simulated correctnesscompared with real data were carried out by measuring GG-IAG fiber. A couplingmodel was introduced to explain the absorption phenomenon during the rayspropagating in the fiber as well.Transparent spectrum, absorption cross-section, emission cross-section andlifetime of our Yb doped material were measured （calculated）. Based on these data theGG-IAG fiber amplifier is investigated with a rate equation model. Meanwhile, theinfluence of negative index step on gain characteristic has also been studied, as wellas the output characteristics of a GG-IAG fiber amplifier with different pump ways.A3-D heat analytical model was established, and simulations of the temperaturefield in GG-IAG fiber amplifier are performed based on the rate equations. With thismethod we compared the temperature field distribution with and without longitudinal heat flow under natural convection cooling. Meanwhile, the influence of differentpump directions, cooling methods, cladding radius, negative refractive index step onthe temperature distribution has been studied as well.All of these researches may give some suggestions on design and optimization ofthe GG-IAG fiber.Chalcogenide glasses （ChGs） have attracted a lot of attentions not only for theirunique properties like good glass-forming ability, large transmission window, lowphonon energy, large values of refractive index, but also for their ability to dissolve upto few atomic percent of rare-earth （RE） which makes them highly promising as REhost materials for optical amplifier applications where high doped concentration ofRE is required urgently for the reduced length of integrated optical amplifiers. Amongvarious glasses available, heavily doped with Er3+ions glasses are prospectivematerials for the1.54μm emission arising from4I413/2â†'I15/2transition.In the second part of this work, the properties of Ge_11.5As₂₄Se_64.5chalcogenidethin films into which Er atoms were ion implanted at energies of2.25MeV up to aconcentration of0.4mol%were studied. The effect of post implant annealing wasinvestigated on the luminescence from4I⁴13/2â†'I15/2transition of Er as well as on thephysical properties of the films.