Design and implementation of ultra-high resolution, large bandwidth, and compact diffuse light spectrometers

To realize spectrometers with state-of-the-art performance measures, we need to combine novel synthetic material properties and new device concepts using efficient design and optimization tools. Considering the material engineering, device innovation, and modeling and simulation tool development as the three primary areas of research in the invention of modern spectrometers, I put myself at the intersection of these three areas. My Ph.D. research has been focused on the development of such infrastructures for next generation spectrometers.;My research on the new concepts for spectrometer has been focused on the development of true multi-dimensional spectrometers, which use a multi-dimensional [two-dimensional (2D) or 3D] mapping of the spectral information into space. While the conventional spectrometers use a grating to form a one-dimensional (1D) spatial-spectral mapping, I showed that by combining a simple dispersive element (a volume hologram) formed in very inexpensive polymers with a basic Fabry-Perot interferometer, we can form a spectrometer with ultra-high resolution over a large spectral bandwidth, which surpasses all conventional spectrometers. This unique performance is obtained by the 2D spatial-spectral mapping enabled by combining two simple optical functionalities. I strongly believe that the extension of this mapping into three dimensions by using synthetic nanophotonic structures with engineered dispersion (optimized using the recently demonstrated modeling tool) can further improve the performance and reduce the overall spectrometer size into the micron regime.;The need for efficient modeling and simulation tools comes from the sophisticated nature of the new 3D nanophotonic structures, which makes their simple analysis using well-known simple formulas for the propagation of the electromagnetic fields in bulk materials impossible. On the other hand, direct numerical simulation of these structures using the well-known numerical simulation tools such as finite difference time-domain or the finite element techniques is not possible due to the excessive requirement of memory and simulation time. Added to the complexity of the problem is the diffuse (or spatially incoherent) nature of the optical beams in the state-of-the-art spectroscopy applications. In my Ph.D. research, I developed new approximate modeling tools for both the modeling of incoherent sources in nanophotonics, and for the propagation of such optical beams inside the 3D nanophotonic structures of interest with several orders of magnitude improvement in the simulation speed for practical size devices without sacrificing accuracy. I believe the tools developed in my research enable us to look into new structures and functionalities that we were not able to analyze simply before.;To enable new dispersive properties using a single nanophotonic structure, I have focused in my Ph.D. research into polymer-based 3D photonic crystals, which can be engineered using their geometrical features to demonstrate unique dispersive properties in three dimensions that cannot be matched by any bulk material even with orders of magnitude larger sizes. I have demonstrated the possibilities of using a very compact structure for wavelength demultiplexing and also for spectroscopy without adding any other device. The range of applications that can be enabled by having a material system with a wide range of 3D dispersive properties is very wide covering spectroscopy and sensing, dispersion management, diffraction compensation, pulse shaping, and many others. I am very interested in using this material platform and extend my current research into 3D heterostructures in which each portion of the structure is engineered to optimize a subset of optical functionalities. The simplest version of such heterostructures is the integration of interferometry and spectroscopy in a single structure. The most general view of such engineered nanostructures is to consider them as a 3D version of the gratings for the spatial-spectral mapping of the information in an optical beam.