Scattering Metal Waveguide Based Speckle-Enhanced Prism Spectrometry

We present an optical efficiency improved speckle spectrometer where a scattering metal wave-guide is utilized along with a conventional prism spectrometer. We conducted extensive tests on 25 different scatterers, involving a variety of nanoparticle concentrations, scattering layer thicknesses, and wave-guide vs. non-guiding type scatterers. We observed 35 pm spectral resolution at 1.3% optical efficiency, which we could only achieve with ∼0.01% optical efficiency using a conventional non-guiding scatterer. Thus our new implementation provides up to two orders of magnitude improvement in optical efficiency at the same spectral resolution, as opposed to scatterers that are not sandwiched between metal plates. The improvement in optical efficiency allows for rapid (∼5 μsec exposure) acquisition of the spectrum with a conventional CMOS camera. Thanks to its excellent spectral resolution and diminished optical losses, the proposed spectrometer could be utilized in high frame-rate, real time spectrum reconstruction applications, such as Optical Coherence Tomography.