Plasmon resonance enhanced colloidal HgSe quantum dot filterless narrowband photodetectors for mid-wave infrared

Narrowband detection of mid-wave infrared is of great importance for many applications including thermal imaging and scientific research. Detection of narrowband signals is typically achieved by using broadband photodetectors combined with interference filters or interferometric optics, which inevitably increase the architectural complexity and transmission loss. Here, we report an uncooled and filterless narrowband photodetector for the detection of mid-wave infrared with an enhanced photoresponse by plasmon resonance. Colloidal HgSe quantum-dot films were employed as sensing materials with narrowband optical absorption due to the intraband 1S(e)-1P(e) transition. Furthermore, gold nanodisk arrays were designed, fabricated and integrated with the HgSe quantum-dot films. Based on the nearfield resonance created by the nanodisk structure, the responsivity at the center wavelength of the HgSe quantum-dot film based narrowband photodetector can be increased. In our experiments, four narrowband photodetectors with tunable center wavelengths of 4.2 mu m, 6.4 mu m, 7.2 mu m and 9.0 mu m were fabricated. After the integration with the plasmonic nanodisk array, the responsivity at the center wavelength of the four fabricated narrowband photodetectors was enhanced by 517%@ 4.2 mu m, 288%@ 6.4 mu m, 257%@ 7.2 mu m, and 208%@ 9.0 mu m, reaching up to 145 mA W-1, 92.3 mAW(-1), 88.6 mA W-1, and 86 mA W-1, respectively. The results demonstrated that the full-width at half-maxima of spectral responsivity was also decreased by 42.9% to 59.9% after the integration of the plasmonic nanodisk array. The full-width at half-maxima for four types of photodetectors were all below 2 mm (center wavelength-full-width at half-maxima: 4.2-1.05 mu m, 6.4-1.15 mm, 7.2-1.25 mu m, and 9.0-1.75 mu m), indicating a very sharp spectral photoresponsivity.