Multiaperture Fourier spectrometers in planar waveguides Mirosław Florjańczyk a,b , Pavel Cheben b , Siegfried Janz b , Boris Lamontagne b , Jean Lapointe b , Alan Scott a,c , Kenneth Sinclair a , Brian Solheim a , and Dan-Xia Xu b a CRESS Space Instrumentation Laboratory, York University, Toronto, On, M3J 1P3, Canada b Institute for Microstructural Sciences, National Research Council, Ottawa, On, K1A 0R6, Canada c COM DEV Ltd., Ottawa, On, K2K 3J1, Canada ABSTRACT We present multiaperture stationary spectrometers in planar optical waveguides. The devices are based on the spatial heterodyning technique, do not require moving parts, and use Fourier transformation for spectra retrieval. The design is based on arrays of waveguide interferometers with linearly increasing optical path delay. The spectrometers have increased optical throughput due to multiple input waveguides. We discuss design, fabrication, and first experimental results for these multiaperture spectrometers implemented in silicon-on-insulator (SOI) ridge waveguides. Keywords: spectrometers, waveguides, Fourier spectroscopy, optical circuits 1. INTRODUCTION Development of miniature infrared spectrometers that are robust and environmentally reliable is of great interest for space-borne sensing and spectral imaging. It is important that miniaturization of the instrument does not compromise its performance and the instrument gathers as much light as possible. In classical optics instrumentation, it is known that interferometric spectrometers have the advantage of increased throughput (étendue) compared to dispersive spectrometers at comparable resolution [1]. A widespread use of scanning Fourier interferometers in infrared spectroscopy attests to that advantage. However, in space applications moving mirrors and mounts required for scanning in FT spectrometers pose problems of size, mass, and reliability. An interferometric technique that requires no moving parts in the spectrometer is the spatial heterodyne spectroscopy (SHS) and is based on Fourier transformation of stationary interference pattern [2]. It has been demonstrated that the spatial heterodyne spectrometer is capable of offering a substantial flux throughput over its conventional counterpart [3]. The SHS technique relies on interference of two wavefronts forming a spatial intensity pattern at the output, which unambiguously represents the input spectrum. The Fourier method is used to retrieve the input spectrum from the output interferogram. A monolithic glass SHS device was developed for observations of hydroxyl emission in Earth’s atmosphere in the ultraviolet spectral region [4], while a near-infrared version of such an instrument has been designed for spatial heterodyne observations of water (SHOW) [5]. The SHS principle has also been proposed in planar waveguide optics as a wavelength-dispersive device based on a Fourier-transform Michelson-type arrayed waveguide grating [6]. The essential feature of SHS is the formation of interference fringes of distinct spatial frequencies for different input wavelengths. The instrument is designed such that for the specific input wavelength λ 0 (the Littrow condition) there is no fringe pattern at the output, while fringes of different spatial periods are formed for inputs at other wavelengths. Following this simple idea of unambiguous relation between wavelengths and spatial frequencies of the interference fringes, devices can be developed that do not necessary use interference of continuous wavefronts, but are based on sampled wavefronts to produce discrete fringes. Such a device has been proposed as a multiaperture planar waveguide spectrometer formed by arrayed Mach-Zehnder interferometers (MZI) [7, 8]. The advantage of using MZIs is apparent in planar waveguide optics, where photolithographic processes enable fabrication of well controlled layout patterns, including the MZIs. In the arrayed MZI device, each interferometer samples the input wavefront independently, thus greatly increasing the light gathering capability of the spectrometer as compared to a device with single waveguide input. In this paper, we review our recent advancements in the development of the arrayed Mach-Zehnder Fourier spectrometer. We also introduce a new spectrometer concept based on arrayed Fabry-Perot interferometers. We discuss Integrated Optics: Devices, Materials, and Technologies XIII, edited by Jean-Emmanuel Broquin, Christoph M. Greiner, Proc. of SPIE Vol. 7218, 721816 · © 2009 SPIE · CCC code: 0277-786X/09/$18 · doi: 10.1117/12.810724 Proc. of SPIE Vol. 7218 721816-1