FBG Fabrication
Fiber Bragg grating (FBG) is an optical fiber with periodic variations in refractive index of the core along the optical propagation direction. When a broadband light is transmitted from one end of the FBG, FBG reflects a narrow band of light due to the refractive index variations in core, and transmits all other wavelengths. The reflected wavelength, termed as Bragg wavelength (λB), depends on two parameters - grating period (Λ) and effective refractive index of fiber (neff).In the Grating Fabrication facility at IITM, Phase mask technique is used to fabricate the FBGs with different Bragg wavelengths such as 650 nm, 1060 nm, and different Bragg wavelengths in between 1530-1575 nm.
Power scaling of High power fiber lasers is limited by factors such as fiber non-linear effects, occurrence of self pulsing and thermal mode instability.One of ways to mitigate this problem is via Coherent beam combining where several high-power laser beams are combined together coherently to obtain a single beam with higher power and also with increased radiance (brightness).Coherent beam combining is a key pathway to achieving 100 kW power levels required for DEW applications. The basic building block for such beam combined systems is a narrow line-width, non linearity managed kW-class laser with excellent beam quality (M-squared < 1.2).An experimental setup for coherent combining of 2x100W High-power laser beams using a diffractive beam combining element (DBCE) has been conceptualized and implemented
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