Title :
Multilayer thin-film stacks with steplike spatial beam shifting
Author :
Gerken, Martina ; Miller, David A B
Author_Institution :
Edward L. Ginzton Lab., Stanford Univ., CA, USA
Abstract :
This paper demonstrates the use of a single multilayer thin-film stack for generating custom-engineered spatial dispersion, i.e., spatial shift as a function of wavelength. Based on group-velocity effects similar to the superprism effect observed in photonic crystals, this thin-film grating (TFG) device allows for multiplexing or demultiplexing multiple wavelength-division-multiplexed (WDM) channels using a single nonperiodic thin-film stack. We designed a four-channel TFG for coarse WDM applications with 20-nm channel spacing and flat-top passbands. This paper shows that flat-top passbands correspond to a steplike spatial beam shifting with wavelength. The influence of a finite beamwidth on the passband shape is discussed using Fourier decomposition of the beam into plane-wave components. The paper concludes with experimental results for a three-channel TFG demonstrating steplike beam shifting.
Keywords :
Fourier analysis; channel spacing; demultiplexing equipment; diffraction gratings; multiplexing equipment; optical communication equipment; optical design techniques; optical dispersion; optical multilayers; thin films; wavelength division multiplexing; Fourier decomposition; TFG; WDM channels; beamwidth; channel spacing; demultiplexing; flat-top passbands; group-velocity effects; multilayer thin film stacks; multiplexing; photonic crystals; spatial dispersion; steplike spatial beam splitting; superprism effect; thin-film grating; wavelength-division-multiplexed channels; Channel spacing; Demultiplexing; Gratings; Nonhomogeneous media; Passband; Photonic crystals; Shape; Thin film devices; Transistors; Wavelength division multiplexing;
Journal_Title :
Lightwave Technology, Journal of
DOI :
10.1109/JLT.2004.824380
