Characteristics of a multi-mode interference device based on Ti:LiNbO_3 channel waveguide

Abstract

We have analyzed the multi-mode interference effect depending on the wavelength and the polarization states of input beam in a multi-mode Ti:LiNbO(3) waveguide at about 1300 nm region. The transmitted optical signal of a Ti:LiNbO(3) waveguide shows the periodic oscillation as a function of input wavelength. The measured average periodicity of the oscillation in TM and TE polarization beams were about 18 nm and 48 nm, respectively. Actually, the periodicity is determined by the refractive index difference between the two modes (fundamental and first modes). Therefore, we have explained the experimental results with the theoretical calculations which are derived from a quasi-analytical technique based on the effective-refractive- index method and the equation of coupling length determined by the mode phase factor in the multi-mode waveguide.

Nonperiodic Oscillation With Wavelength of Mode Guided in a Special Ti-Diffused $\hbox{LiNbO}_{3}$ Waveguide Structure

“…First of all, we can exclude several possibilities, such as the coupling between the strip and the planar waveguides (because the light power does not lose from the strip waveguide except for the usual waveguide loss), the coupling among the strip waveguides (because the separation each other is large enough, i.e., 200 m), and the interaction between the TE and TM modes. The observed waveguiding characteristic is very similar to that of MMI, which was observed in a usual multimode Ti:LN strip waveguide [9], [10]. However, the waveguiding characteristic here appears to take place in a single-mode waveguide.…”

Fabrication and optical characterization of long-range surface-plasmon-polariton waveguides in the NIR

“…For a small lateral displacement (less than the mode field diameter) of the optical fiber with respect to the plasmonic gold-stripe both the fundamental and first-order LRSPP modes are excited, yet with different excitation amplitudes. Because these modes exhibit different effective refractive indices (1.553 and 1.549 at λ = 780 nm for the fundamental and first-order mode, respectively) they pick up different phases during propagation and at the end of the waveguide both modes add up coherently, resulting in a multi-mode interference pattern [23,24]. As such interference pattern depends sensitively on the ratio of amplitudes and the phase between both LRSPP modes, experimental analysis of the modal behaviour of our LRSPP waveguides has to take this into account.…”

Surface plasmon polariton enhanced by optical parametric amplification in nonlinear hybrid waveguide

“…However, most of these works were carried out in crystal optics regime without emphasizing the spatial confinement. To achieve an efficient optical parametric process in a waveguide or plasmonic system still remain considerable difficulties [18][19][20][21]. More recently, the QPM technique was theoretically proposed to realize the plasmonic frequency conversion by adopting the periodically poled nonlinear crystal as the dielectric environment [22], but it consequently increases the complexity in structure fabrications.…”

“…To be specific, we consider silver for the metal substrate and LiNbO 3 for the anisotropic nonlinear dielectric that forms a conventional dielectric planar waveguide [20]. For simplification, the dielectric constant of the high index layer (middle LND1 layer) is simply defined by ε 1i = ε 2i + 0.04 (i = x,y,z), corresponding to a numerical aperture of about 0.2 for the conventional dielectric waveguide, where ε 2i is permittivity tensor elements of common LiNbO 3 [23].…”

“…since the integration over the longitudinal components (d 31 , d 22 and E i,x ) is too small and can be neglected as well as Ref. 20. The thickness of the middle layer (NLD1) is set to be 3μm.…”