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Resolving pm wavelength shifts in optical sensing

 

Reflection or transmission properties of one and two-dimensional photonic crystals are widely used for optical sensing applications. A variety of optical sensors exist that change their optical properties upon a stimulus. A compact wavelength detector that is capable to resolve very small changes in the spectral output of these sensors is highly desirable. A photodiode array (PDA) or position sensor device (PSD) in combination with a linear variable bandpass filter features a very rigid and compact device to detect those changes. The filter converts the wavelength information of the incident light into a spatial intensity distribution that is analyzed by the photodetector. We have investigated the performance of these wavelength detectors depending on the optical properties of the filter. This includes the gradient with which the transmission function changes across the filter surface and the FWHM of the transmission function. Also, we point out differences between the PDA and the PSD and analyze the influence of inhomogeneous illumination of the unit.

 
citation

Schmidt, O. ; Kiesel, P. ; Mohta, S. ; Johnson, N. M. Resolving pm wavelength shifts in optical sensing. Applied Physics B - Lasers and Optics. 2007 March; 86 (4): 593-600.