With the development of precision optical engineering, higher manufacturing qualities are demanded for advanced optical systems. The characterization of the surface topographies of optical elements is required to be more specific and more comprehensive. In this paper, the contourlet transform is adopted to extract the topological features of optical elements. The performance of the contourlet transform(CT) is analyzed carefully. The multiscale analysis techniques based on contourlet transform for peak/pit extraction, tool trace identification and sharp edge detection on non-smooth microstructured optical surfaces were shown. The experimental examples are given to demonstrate the validity of the proposed method.
Nonlinear dynamics associated with polarization switching (PS) in a 1550 nm vertical-cavity surface-emitting laser (VCSEL) with orthogonal optical injection is investigated theoretically by scanning the injected power. The results show that, adjusting injected powers may induce complex variation of dynamical state of each polarization mode and PS. When the PS happens, its dynamical states can be located at an injection locking state or not, which depends on the frequency detuning between the injected field and the VCSEL. Detailed mappings of polarization-resolved nonlinear dynamical states are calculated to unveil a rich variety of dynamical scenarios for different scanning routes of injected power in the parameter space of injected power and frequency detuning, and show that the dynamical states and PS are critically dependent on the scanning routes of the injected power under the case of larger current.
We numerically study the nonlinear switching characteristics of optical transmission through optimized fiber Bragg
grating with a π phase shift. The nonlinear coupled-mode equations were solved numerically based on the
time-dependent transfer-matrix method. The result shows that the π phase shift grating is superior to the uniform
grating in the enhancement, corresponding to the local intensity of the light inside the grating. It shows that the use of
π phase shift gratings reduces effectively the switching threshold, but the on-off contrast is generally declined which
can be generally improved through the introduction of tapered parameters. In addition, the narrowed transmitted pulse
for positive-tapered nonlinear Bragg grating is a Bragg soliton owing to the balance of anomalous group velocity
dispersion and self-phase modulation (SPM). It can be found that the tapered nonlinear Bragg grating with a π phase
shift is more preferable for achieving the larger on-off contrast.
A novel chaotic synchronization configuration is proposed. This system is constructed on the basis of unidirectionally
coupled VCSELs and signal transmission in fiber. The transmitter VCSEL is subject to an isotropic optical feedback, the
receiver VCSEL is subject to an orthogonal optical injection from the transmitter VCSEL, the chaotic signal transmission in fiber channel is adopted, also message encoding and decoding of the chaotic system have been investigated. The results show that, during to the fiber nonlinear and chromatic dispersion, the amplitude characteristics of chaotic signal are distorted partially and the system synchronization quality will be impaired, but message can be hidden efficiently in the chaotic signal during the fiber transmission with additive chaos modulation (ACM). Better decoding performance is achieved by choosing appropriate matched parameters.