For the first time, we demonstrate the implementation of a core pumped few mode erbium amplifier utilizing a mode selective photonic lantern for spatial modal control of the pump light. This device is able to individually amplify the first six fiber modes with low differential modal gain. In addition, we obtained differential modal gain lower than 1 dB and signal gain of approximately 16.17 dB at λ<sub>s</sub> = 1550 nm through forward pumping the LP21 modes at λ<sub>p</sub> = 976 nm.
We present a time dependent computer model for modal instabilities (MI) in high power fiber amplifiers based on beam propagation method. Three regimes of temporal dynamics that are characteristic of the transfer of energy between the fundamental mode and higher order mode are captured and applied to predicting the threshold of these instabilities in absence of any frequency offset between the interfering modes. Simulation results show an increase of the instabilities threshold by a factor of approximately %30 in the case of bi-directional pump scheme with respect to the forward pump configuration. Furthermore, we estimated the MI threshold applying a coupled-mode model of thermally induced instabilities which also takes account of gain saturation to its first order approximation, and obtained reasonably good agreement with respect to our beam propagation simulation results.
We discuss the design and development of a slow-light spectrometer on a chip with the particular example of an
arrayed waveguide grating based spectrometer. We investigate designs for slow-light elements based on photonic
crystal waveguides and grating structures. The designs will be fabricated using electron-beam lithography and UV
photolithography on a silicon-on-insulator platform. We optimize the geometry of these structures by numerical
simulations to achieve a uniform and large group index over the largest possible wavelength range.
Abstract We introduce the simulation of a photonic crystal slab with a square lattice, whose basis elements are layered cylinders of an averaged refractive index <n>. We compare it with a similar photonic crystal with a basis of the same size and a refractive index matching to the average of the layered ones. Even when this is such a simple system with internal structure, we have found an interesting phenomenology: an increase in band gaps, flattening of the bands, degeneracy nodes, etc. We also introduce additional methods to fine tuning the design and analyze the inclusion of a plain cylinder defect within the slab.
In the present work we analyze the nonlinear modes of silicon-on-insulator (SOI) nanowires and supermodes of the
coupled SOI waveguides. A generalized analysis of the nonlinear modes of silicon nanowires is given where we have
considered the scalar approximation and its vectorial nature to obtain the analytical profiles. In the scalar approximation,
the analytical analysis of the profiles of the transversal modes is based on the solutions of the Helmholtz equation for
nonlinear periodic media, where we obtain an integral solution for the intensity which is identified with the help of the
elliptic functions. Those modes are characterized by two constants of motion of particular physical significance and in
some approximations the solution could become a soliton or cosenoidal type. Therefore, we describe the solutions on
terms of the movement and integration constants. This is an important result because defines the nature of the solutions,
therein the analysis of the third order polynomials roots of those elliptic functions. The general theoretical model
includes the two-photon absorption (TPA) and the nonlinear Kerr effect implicit in the refraction index.