Fig. 1. Characterization of one resonant-cavity-enhanced CQD homojunction photodetector. (a) Schematic structure of the detector is depicted on the left. The upper-right inset displays a cross-sectional scanning electron microscopy (SEM) image of the device, and the bottom-right inset shows a magnified image of the CQD layer. Scale bar: 500 nm. (b) Electric field distribution of the detector. (c) Simulated absorption of CQD layer with different spacer thicknesses. (d) Simulated absorption of CQD layer with different gold contact thicknesses. (e) Simulated absorption of CQD layers with different upper gold thicknesses. (f) Simulated absorption of CQD layer with different CQD thicknesses.

Fig. 2. Resonance-enhanced CQD homojunction device characterization. (a) I–V curves comparing detectors with and without resonant-cavity-enhanced microstructures. (b) Noise spectra comparing detectors with and without resonant-cavity-enhanced microstructures. (c) Response spectra comparing detectors with and without resonant-cavity-enhanced microstructures.

Fig. 3. HgTe CQD spectrometer. (a) The detector line array and data processing section, and the schematic diagram of the line array post-processing circuit is shown on the right. (b1) Voltage spectra calculated following Eq. (1). (b2) Directly measured photovoltage spectra. (c) Response spectra of the detector at different positions. (d) Spectrogram after spectral differentiation from (c).

Fig. 4. Reconstructed spectrum. (a) Plot of photovoltage as a function of x at different positions before and after placing the sample. (b) Schematic spectral response curves for 256 different positions xn. (c) Comparison of spectra obtained with a commercial Fourier transform spectrometer and reconstructed spectra.

Fig. 5. Picture of the detector array. (a) 4-inch wafer without drop-casting HgTe CQD. (b) 4-inch wafer after drop-casting HgTe CQD. (c) Line array detector with 256 pixels.

Fig. 6. Response speed of single pixel device.

Fig. 7. The I–V curves and CQD layer thickness tests. (a) I–V curves and 340 nm QD layer thickness tests for a resonant cavity-enhanced detector and a microstructured detector without a resonant cavity. (b) I–V curves and 470 nm QD layer thickness tests for a resonant cavity-enhanced detector and a microstructured detector without a resonant cavity. (c) I–V curves and 600 nm QD layer thickness tests for a resonant cavity-enhanced detector and a microstructured detector without a resonant cavity. (d) I–V curves and 400 nm QD layer thickness tests for a resonant cavity-enhanced detector and a microstructured detector without a resonant cavity.

Fig. 8. The I–V curves of other channels among the 256 pixels.

Fig. 9. Simulation of quantum dots with different response wavelengths for devices of the same structure. (a) Simulated absorption of HgTe layers with different spacer thicknesses. (b) Simulated absorption of HgTe layers with different quantum dot thicknesses. (c) Spectral response of devices with and without resonant cavity enhancement.

Fig. 10. Pictures of grating microscope observations. (a) 1 mm/100, (b) 1 mm/300, (c) 1 mm/600.

Fig. 11. Physical picture of the detector array and the grating elements.

Fig. 12. Algorithm flow chart.

Fig. 13. Training datasets comprising photovoltage and spectral eigenvalue. (a) Spectral response of a detector with resonant cavity at different xn, (b) spectral integration, (c) measured voltage. (d) Transmittance of filter 1. (e) Spectral response of a detector with resonant cavity enhancement under the condition of filter 1 at different positions, (f) measured voltage. (g) Transmittance of filter 2. (h) Spectral response with resonant cavity enhanced detector under the condition of filter 2 at different positions, (i) measured voltage.

Fig. 14. Neural network self-learning filter transmittance library with (a) transmittance peaks of about 2.3 μm, (b) transmittance peaks of about 1.7 μm, and (c) transmittance peaks of about 1.9 μm.

Fig. 15. Schematic of the detector line array movement and the data processing section. (a) Schematic of the detector line array movement. (b) Spectral response curve when the line array detector is located at xn′. (c) Integral plot of spectral curves. (d) Spectrogram of panel (b) after performing spectral differencing.

Table 1. Comparison of NIR Spectrometers between Reported Works and This Work