13 February 2012 Flat spectral response all-digital broadband variable fiber optic attenuator
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Abstract
The Texas Instruments (TI) digital micromirror device (DMD) is inherently a two dimensional (2-D) blaze grating that causes wavelength-dependent angular spreading of reflected broadband light limiting its use as a broadband variable fiber optic attenuator (VFOA). In this paper, we propose a novel design that utilizes a double-reflection architecture to counter angular spreading while at the same time eliminates the need to use any narrowband components such as wave plates thus delivering a truly flat spectral response VFOA. The key feature of this design is that the DMD, instead of being oriented in the Littrow retro-reflective configuration for the center wavelength, is oriented at a different angle to the input beam such that the blaze condition is still satisfied albeit for a different diffraction order n. The only wavelength dependent loss (WDL) in this design is due to the fact that the blaze condition is satisfied only for a center wavelength λc at which the diffraction efficiency is maximum while at other wavelengths, the blaze condition is not perfectly satisfied resulting in a loss in diffraction efficiency. Simulation results show a WDL of only 0.01 dB over the C-band compared to the previously reported experimental value of ±0.37 dB thus resulting in a truly flat spectral response VFOA.
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Mumtaz Sheikh, Mumtaz Sheikh, } "Flat spectral response all-digital broadband variable fiber optic attenuator", Proc. SPIE 8254, Emerging Digital Micromirror Device Based Systems and Applications IV, 82540P (13 February 2012); doi: 10.1117/12.907415; https://doi.org/10.1117/12.907415
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