Infrared spectrometers have significant applications in industry and laboratories. However, traditional infrared spectrometers, such as grating-based and Fourier-transform infrared (FTIR) spectrometers, are space-consuming and expensive. They require liquid nitrogen cooling, greatly limiting their applications in portable devices and broader applications.

Computational spectrometers, utilizing arrays of micro-sized detectors with tunable response spectra and reconstruction algorithms, eliminate the need for large components like gratings and interferometers found in traditional spectrometers, resulting in a significant reduction in size. Furthermore, employing electrical methods like gate voltage to nonlinearly modulate the photoresponse spectra of individual detection elements can replace the spatial dimensions of detector arrays, significantly reducing the size of computational spectrometers. Two-dimensional material black phosphorus (BP), with tunable bandgap, van der Waals layered structure, and high mid-infrared responsiveness, provides an excellent material platform for on-chip micro-infrared spectrometers.

Assistant Professor Xiaolong Chen’s research team from the Department of Electronic and Electrical Engineering at the Southern University of Science and Technology (SUSTech) has recently demonstrated a miniaturized room-temperature infrared spectrometer based on a single BP-MoS₂ heterostructure.

Their work, entitled “Room-Temperature Self-Powered Infrared Spectrometer Based on a Single Black Phosphorus Heterojunction Diode”, has been published in Nano Letters, a top journal covering all aspects of nanoscience and nanotechnology and their subdisciplines.

This study presents an on-chip micrometer-scale infrared spectrometer operating at room temperature based on a single BP-MoS₂ van der Waals heterostructure, as illustrated in Figure 1a. By utilizing the quantum-confined Franz-Keldysh effect, Stark effect, Moss-Burstein effect, and other optoelectronic effects induced by the gate voltage, the light responsivity curve of the BP-MoS₂ heterostructure exhibits nonlinear changes with gate voltage (Figure 1b). When an unknown incident spectrum irradiates the BP-MoS₂ heterostructure, the spectrum of the incident light can be calculated by measuring the photocurrent at different gate voltages (Figure 1c) and combining reconstruction algorithms (Figure 1d). The device is capable of operating in a wide wavelength range of 1.7–3.5 micrometers at room temperature, with a footprint of only 30×50 μm^2, significantly smaller than that of traditional infrared spectrometers, offering new possibilities for photonic chip integration.

Figure 1. (a) Schematic structure diagram of the BP-MoS₂ spectrometer. (b) Responsivity matrix of the BP-MoS₂ spectrometer depending on gate voltage V_g and wavelength. (c) Photocurrent-gate voltage curve under illumination from a blackbody radiation source. (d) Comparison of reconstructed spectrum curve of miniaturized BP-MoS₂ spectrometer (blue) with measured spectrum by a commercial FTIR spectrometer (orange).

Han Wang, a doctoral candidate at SUSTech, is the first author of this paper. Assistant Professor Xiaolong Chen is the corresponding author, and SUSTech is the first communication unit.

The work was supported by the Shenzhen Excellent Youth Program, National Natural Science Foundation of China (NSFC), Shenzhen Basic Research Program, and the Guangdong Major Talent Project. The authors also acknowledge Yun Wang and Chun Cheng for their support with thickness characterization.

Paper link: https://pubs.acs.org/doi/10.1021/acs.nanolett.3c04044

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