On 27th April 2015, Tigran Baghdasaryan successfully defended his Ph.D. thesis entitled "A study of multi-photon inscription of fiber Bragg gratings in glass microstructured optical fibers" in a public session. During his defense he explained how the turn of the 21st century has marked the introduction of a new type of optical fibers, known as ‘Microstructured Optical Fibers’ (MOFs). Their cross-section is also commonly made of glass, but now with a specific pattern of air holes that run along the entire length of the fiber. MOFs feature unprecedented design flexibility when compared to conventional optical fibers. This stems from the freedom to adapt the lay-out of the air hole pattern and to modify the distance between the holes and their diameter. A current hot topic in the domain of optical fiber technology is to develop all-MOF based devices including MOF based lasers and MOF based sensors. To do so one is currently seeking to combine fiber Bragg grating (FBG) technology with MOF technology. A FBG is a periodic variation of the refractive index in the core of an optical fiber, which acts as a wavelength selective mirror or filter. It is typically fabricated by transversely exposing the MOF core to intense laser light and consequently modifying the refractive index of the glass within this core. Fabricating FBGs inside MOFs has proven not to be straightforward. The holey structure of the MOF usually prevents the delivery of intense laser light to the core region, which complicates the formation of the required refractive index changes. This problem is exacerbated when employing new FBG fabrication methods that require the use of very high intensity laser pulses with short duration. The general objectives of Tigran's Ph.D. thesis were articulated around this concern and were as follows: to understand the issues encountered when fabricating FBGs in MOFs with short laser pulses and to find possible solutions for improving grating fabrication in MOFs by exploiting the design flexibility of the air hole pattern. He established a dedicated methodology based on numerical modeling to study FBG fabrication in MOFs and used this methodology to design new MOF structures that will facilitate the manufacturing of FBGs in their core. Check out Tigran's latest scientific publication here .
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