VIPA (Virtually Imaged Phased Array) based spectrometers are now routinely favoured over other types of spectrometers (such as scanning Fabry-Perot) for Brillouin imaging because VIPAs permit higher data acquisition speeds as compared to others. However, higher speeds mean lower photon counts at the camera used to acquire the spectra. The quality of optical components used is also important and have profound effect on the quality of the spectrum. Yet, these issues have not been addressed by various groups doing Brillouin imaging around the world. In this talk we examine the effect of the various optical components on the overall performance of the spectrometer both in one and two stage configuration. We define information content in the measured spectra and using information theoretic approach determine system parameters under various design conditions. We show for example, the spherical aberration imparted by the plano-convex cylinder lens usually placed at the entrance of the spectrometer reduces signal quality but it otherwise does not affect the accuracy of measurements. On the other hand, aberrations introduced by lenses further down the optical train may result in significant loss in localisation accuracy of the spectra. Our approach will aid users of VIPA based spectrometers designing better quality systems.
ChengZe Song, Emilio Sánchez-Ortiga, Matthew R. Foreman, and Peter Török, "Optimisation of a single stage VIPA spectrometers (Conference Presentation)," Proc. SPIE 10067, Optical Elastography and Tissue Biomechanics IV, 100670N (Presented at SPIE BiOS: January 29, 2017; Published: 24 April 2017); https://doi.org/10.1117/12.2255054.5380018833001.
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Study of self-shadowing effect as a simple means to realize nanostructured thin films and layers with special attentions to birefringent obliquely deposited thin films and photo-luminescent porous silicon