Techniques for reading the spectral content of a spatial-spectral grating in an inhomogeneously broadened transition (IBT) material include directing multiple probe waveforms to probe a spatial mode of the IBT material. Each probe waveform is a linear frequency modulated chirp; each probe waveform partially overlaps in frequency with a different probe waveform; and multiple output signals are detected from the IBT material in response. Based on the multiple output signals, a readout signal is determined that represents a complete or nearly complete temporal map of the spectral content of the spatial-spectral grating. Calibration of the frequency content can be achieved by simultaneously reading out calibration spectral features. These techniques allow high-bandwidth spectral content to be read with segmented narrow bandwidth chirp probe waveforms and low-bandwidth high-dynamic-range detectors and digitizers.