We study the optical switching of the two-dimensional nonlinear coupler in a doped photopolymer. The coupled nonlinear Schrödinger equations (CNLSEs) describing our coupler system are analysed using Lagrangian variational method. From the Lagrangian, a set of coupled ordinary differential equations (ODEs) describing the system dynamics is obtained. This set of ODE’s is further reduced to single coupled equation and an analytical solution is obtained using the cnoidal functions and the system dynamics is studied. The key factor for switching mechanism of our coupler system is the metal-induced surface plasmon resonance (SPR). This SPR-induced local nonlinear effects results in self-focussing of the optical beam through the launched core. A description of a particle in a well is also made to study the photon switching through the coupler system.

We aim to study the nonlinear optical phenomena with ultra-broadband radiation in photonic crystal fibre (PCF). While PCFs with cores made from different glasses are well studied in previous works, in this paper, it is planned to investigate the dynamics of nonlinear processes of supercontinuum generation (SCG) in liquid-filled PCF (LCPCF) to understand the physical phenomena of femtosecond pulse propagation, particularly, the temporal and spectral changes of the pulse propagating through specific PCFs. Since the CS₂-filled LCPCF has complex nonlinear phenomena, we intend to analyse the role of saturable nonlinear response and slow nonlinear response on SCG in detail. For the physical explanation, soliton fission and modulational instability techniques will be implemented to investigate the impact of slow nonlinear response and saturable nonlinear response respectively, in SCG process.

We numerically observe the effect of homogeneous magnetic field on the modulationally stable case of polar phase in $F = 2$ spinor Bose–Einstein condensates (BECs). Also we investigate the modulational instability of uniaxial and biaxial (BN) states of polar phase. Our observations show that the magnetic field triggers the modulational instability and demonstrate that irrespective of the magnetic field effect the uniaxial and biaxial nematic phases show modulational instability.

A theoretical analysis of modulational instability (MI) of optical pulses propagating near the zero dispersion wavelength of a lossless fibre with the effect of delayed saturable nonlinear response is presented. We calculate the exact dispersion relation with the effect of higher dispersion for the harmonic perturbation. We analysed the impact of fourth-order dispersion effects in the MI spectrum. We examine the possibility of MI in both dispersion regimes, regardless of the sign of the group velocity dispersion.

We present a practical design of novel photonic crystal fibre (PCF) to investigate the nonlinear propagation of femtosecond pulses for the application of optical coherence tomography (OCT) based on supercontinuum generation (SCG) process. In addition, this paper contains a brief introduction of the physical phenomena of soliton and SCG. Typically, here we discuss how the ultrabroadband radiation in PCF can be generated by SCG through various nonlinear effects of the fibre. To accomplish the proposed aim, we put forth liquid core PCF (LCPCF) structure filled with chloroform for OCT measurements of the eye. From the proposed design, we observe that proposed LCPCFs with liquid material exhibit significant broadened wavelength spectrum with low input pulse energy over small propagation distances for the OCT application.