Integrated echélle gratings for astrophotonics

In pursuit of miniaturization of spectrograph systems, various wavelength-dispersive technologies such as arrayed waveguide gratings (AWGs) [1] and stationary-wave integrated Fourier transform spectrographs (SWIFTS) [2] have been studied as possible candidates for practical implementations of compact, lightweight integrated spectrographs. Integrated echélle-grating (EG) based wavelength demultiplexers have been proposed as an alternative to AWGs for use as the main diffractive element in such a compact spectrograph [3]. Apart from the simple Rowland mount type, more sophisticated geometries, such as the perfect chirped grating (PCG) [4] and two-stigmatic-point gratings (SEG) [5] exist. In this work, we present the first planar integrated echélle grating based on SEG geometry and specifically designed for astronomical spectroscopy in the NIR range ~1500 nm to 1600 nm.