Fig. 1. Principle of a concave grating miniature spectrometer. (a) A conventional concave grating spectrometer with one entrance slit. (b) The new concave grating spectrometer with two entrance slits. (A, A1, A2, B1, B2, Bλ1, Bλ2, and Bλ3 are all located in the meridional plane XOY. P is an arbitrary point in the grating).

Fig. 2. Simulated spectral bands and spectral resolutions in the whole slit. (a) Spectral resolutions of the two different types of spectrometers in the spectral range of 400–900 nm, and (b) spectral resolution of the new spectrometer in the spectral range of 900–1200 nm.

Fig. 3. Experimental setup for resolution testing. (a) A fiber is set on the position of entrance slit A1 for testing the spectral band of 400–800 nm. (b) A fiber is set on the position of entrance slit A2 for testing of the spectral band of 800–1200 nm.

Fig. 4. Measured spectra using the structure of two entrance slits. (a) Spectrum of mercury lamp. Spectra of lasers with a central wavelength of (b) 594.00 and (c) 632.80 nm. (d) Spectrum of Argon lamp. (f) Spectrum by using a supercontinuum source.