High-resolution microspectrometer with an aberration-correcting planar grating

Abstract

A concept for a highly miniaturized spectrometer featuring a two-component design is presented. The first component is a planar chip that integrates an input slit and aberration-correcting diffraction grating with an image sensor and is fabricated using microelectromechanical systems (MEMS) technologies. Due to the fabrication in a simple MEMS batch process the essential elements of the spectrometer are automatically aligned, and a low fabrication cost per device can be achieved. The second component is a spherical mirror, which is the only external part. The optimized grating structure compensates for aberrations within the spectrometer operating range, resulting in a diffraction-limited performance of the spectrometer optics. The prototype of the device has been fabricated and characterized. It takes a volume of 0:5 cm 3 and provides a FWHM spectral resolution of 0:7 nm over a 350 nm bandwidth from 420 nm to 770 nm combined with an etendue of 7:4 × 10 −5 mm 2 sr.

Design and implementation of a sub-nm resolution microspectrometer based on a Linear-Variable Optical Filter

“…However, these two peaks have different shape (FWHM) and because of that the algorithm is tested to check the possibility of separating these two peaks based on their shape. Figure 21 shows the result of the LMS algorithm compared with the spectrum of Neon lamp measured by the commercial spectrometer used in [18]. There is good agreement between the two spectra below 650 nm.…”

“…15b. Figure 16 shows a comparison between the calculated spectra of the Neon lamp from the LVOF data and the spectrum measured by a commercial spectrometer, used in [18], with 2 nm spectral resolution. There is good agreement between the two spectral measurements.…”

“…The commercial spectrometer is unable to separate the different peaks at about 639 nm and the measurement shows a broad peak, whereas with the LVOF-based microspectrometer it was possible to resolve the smaller narrowly spaced peaks at 640.5 and 637 nm. In order to make a better validation of the calculated spectrum, a comparison has been made with a grating-based microspectrometer reported in [18], which features a spectral resolving power of 0.7 nm. Figure 17 shows the comparison.…”

Medical apps in need of optical microspectrometers

“…Using micromachining technologies for fabrication of entire optical systems has proven difficult to achieve, which was mainly because of the incompatibility of planar technology with high-quality spectrometers. The best that can be achieved with a planar grating-based microspectrometer is a resolution of about 10 nm over the 630-730 nm spectral range (Grabarnik et al 2007), which can be significantly improved at the expense of on-chip CMOS-compatibility using an optical design with an external spherical mirror (Grabarnik et al 2008).…”

Compact gas cell integrated with a linear variable optical filter

“…These devices typically involved an electrostatically tunable Fabry-Perot (FP) resonator that was fabricated using bulk micromachining and silicon wafer bonding [3]. Subsequent studies have proposed grating-based microspectrometers for the visible and near-IR spectral range [4,5], MEMS-based Fourier transform infrared spectroscopy (FTIR) systems [6] and FP-based microspectrometers [7]. A special category can be reserved for the microspectrometer that is based on optical components in a waveguiding layer [8].…”