Fabrication and application of holographic Bragg gratings in lithium niobate channel waveguides

Abstract

Permanent refractive-index gratings in waveguide devices are of high potential for optical communication systems that make use of the high spectral selectivity of holographic filters, e.g. dense wavelength division multiplexing (DWDM), optical sensors, or narrow-bandwidth mirrors for integrated waveguide lasers. In this contribution we review our results on holographically recorded refractive-index gratings in Cu-doped LiNbO 3 channel waveguides. Elementary holograms are recorded with green light and read in reflection geometry in the insensitive infrared wavelength region around 1.5 µm. To enable long-term stability of the Bragg gratings a thermal fixing technique is applied. In this way strong and almost permanent refractive-index gratings are obtained and their application as narrow-bandwidth filters for DWDM applications is demonstrated. In comparison with Bragg gratings in silica fibres, the electro-optic effect in LiNbO 3 allows for a direct wavelength tuning and a fast, reliable electrical switching of these gratings.

Exact solutions for bright and dark solitons in spatially inhomogeneous nonlinearity

“…( ) is the strength of the nonlinearity that varies along the direction. In optics, spatially inhomogeneous nonlinearities can be realized by using inhomogeneous doping [5,6]. If is replaced by time , Eq.…”

Multi-Channel Adaptive Interferometers Based on Dynamic Hologram Multiplexing

“…Note as well that such a demultiplexer can be also built on the basis of dynamic holographic grating recorded in a PR crystal (Hukriede, et al, 2003;Petrov, et al, 2001;Petrov, et al, 2003;Runde, et al, 2005). The scheme of such photorefractive band-drop filter proposed in (Petrov, et al, 2003) is shown in Fig.…”

Mode-selective coupler for wavelength multiplexing using LiNbO3:Ti optical waveguides

“…For this purpose, experimental parameters of the waveguide fabrication process are thickness of the evaporated titanium film, width of the lithographically patterned titanium stripes, and in-diffusion conditions (diffusion temperature T and time ). With these values the two-dimensional diffusion profiles T ( , ) of titanium are calculated using literature data for the diffusion constant and index change ∆ ( T ) [15]. Then the wave equation is solved numerically for the resulting index profile ∆ ( , ) by utilizing a finite difference method, resulting in the mode dispersion and the field distributions E( ) of the guided modes propagating in the -direction.…”

“…Alternatively, we have shown that holographic recording of elementary gratings using two-beam interference is an appropriate and efficient technique to record narrowband reflection gratings using the photorefractive effect in LiNbO 3 [14,15]. Compared to other optical materials like glasses or polymers, a multiplexer of the described scheme in LiNbO 3 allows for additional fast electrical switching of the Bragg grating in the GHz regime due to the superior electro-optic properties of this substrate material.…”