Wavemeter Based On Dispersion And Speckle In A Tapered Hollow Waveguide

We demonstrate a broadband wavemeter by imaging the radiation from multiple interfering modes approaching cutoff in a tapered hollow waveguide (clad by omnidirectional Bragg mirrors). Dispersion of the cutoff point was used to extract a coarse wavelength estimate, and subsequent computational analysis of the complex standing wave radiation pattern leading up to the cutoff point enabled a much finer estimate. This approach leverages the principles of speckle-based spectrometers but with added functionality provided by the spectral-spatial dispersion of the mode cutoff position. In proof-of-principle work, we verified a resolution < 10 pm over an operating range of nearly 100 nm in the near infrared using a tapered waveguide with a length < 1 mm. Significantly enhanced resolution should be possible through feasible refinements of the waveguides and peripheral components. (c) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement