Abstract
A blazed chirped Bragg grating in a planar silica waveguide device was used to create an integrated diffractive element for a spectrometer. The grating diffracts light from a waveguide and creates a wavelength dependent focus in a manner similar to a bulk diffraction grating spectrometer. An external imaging system is used to analyse the light, later device iterations plan to integrate detectors to make a fully integrated spectrometer. Devices were fabricated with grating period chirp rates in excess of 100 nm mm-1, achieving a focal length of 5.5 mm. Correction of coma aberrations resulted in a device with a footprint of 20 mm×10 mm, a peak FWHM resolution of 1.8 nm, a typical FWHM resolution of 2.6 nm and operating with a 160 nm bandwidth centered at 1550 nm.
Highlights
The miniaturisation of spectrometers has been an important topic for over 20 years [1,2,3,4,5,6,7,8,9,10]
Doped glass layers are deposited on top of the thermal oxide using flame hydrolysis deposition (FHD); the first of these is a germanium doped photosensitive core, the second is a non-photosensitive cladding that matches the index of the thermal oxide layer
We have shown the ability to remove the effects of coma aberrations, allowing for small footprint devices without compromising the resolution
Summary
The miniaturisation of spectrometers has been an important topic for over 20 years [1,2,3,4,5,6,7,8,9,10]. In general these spectrometers fall into two categories: Fourier transform and dispersive. The input spectrum can be measured from the recorded light distribution across the sensor. It is this dispersive regime that will be investigated in this paper
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