Photodetectors (PDs) for weak light signal detection have wide applications for optical communication and imaging. Antimony sulfide (Sb2S3) as a nontoxic and stable light-sensitive material becomes a promising candidate for weak light PDs, which are developing in the direction of high response, high speed, and low cost. Herein, a self-powered Sb2S3 PD with the structure of FTO/TiO2/Sb2S3/Au is developed to achieve weak light detection for 300–750 nm visible light. We control the Sb2S3 thickness with about 460 nm to match depletion region width (438 nm) and obtain an excellent photoresponsivity and 3 dB bandwidth. Furtherly, we prepare pyramid structure polydimethylsiloxane (PDMS) on the illuminating surface to enhance the performance of weak light detection by light-trapping effects. The photocurrent of Sb2S3 PD with 20 μm-sized PDMS texture achieves 13.6% improvement compared with the control one. Under weak 530 nm light illumination of 1 μW cm–2, the self-powered Sb2S3 PD with PDMS achieves high responsivity (3.41 A W–1), large detectivity (2.84 × 1013 Jones), and ultrafast speed (15 μs). The present Sb2S3 PD and light-trapping strategy are expected to provide an alternative to future commercial weak light detection applications.
Sb 2 S 3 crystals are composed of numerous 1D molecular chains contacted by van der Waals forces, easily forming 1D nanowires. Many scientific researchers focus on the research of Sb 2 S 3 nanowire PDs. The PD based on Sb 2 S 3 nanowires built on Si/SiO 2 by Zhong et al. [14] has achieved the ON/OFF ratio of 210, the responsivity of 1152 A W −1 , and the specific detectivity of 2 × 10 13 Jones. Zhang et al. [15] added Au nanoparticles to the Sb 2 S 3 nanowires and achieved high responsivity (59.5 A W −1 ), but the response speed was still relatively slow (≈0.2 s). Wang et al. [16] used CuSCN to attach to Sb 2 S 3 nanowires, which exhibited a switching ratio of 100 and the response time of 0.15 s. Ye et al. [17] used CVD to prepare high-quality Sb 2 S 3 nanowires. The PD demonstrated a quite large responsivity of 65 A W −1 , excellent detectivity of 2.1 × 10 14 Jones, and short response time of about 76 ms. The above researches show that the Sb 2 S 3 nanowire PD exhibits excellent performance. There are still some aspects that can be improved, such as slow response speed, complicated preparation process, and difficulty in integration. In our previous work, we used the rapid thermal evaporation (RTE) method to fabricate high-quality Sb 2 S 3 film and obtain excellent photoelectric properties for thin film PD. [18,19] The Sb 2 S 3 thin film PDs have advantages in uniformity, integration, and cost. The main performance parameters (responsivity and detectivity) of PDs are fundamentally extracted from photocurrent and dark current, which are limited by Sb 2 S 3 material properties and device structure. Therefore, reducing dark current and increasing photocurrent are the most direct and effective methods to improve the performance of PDs. The device structure, deposition process and performance of Sb 2 S 3 PDs need to be further investigated and developed.As a 1D ribbon material, Sb 2 S 3 exhibits strong anisotropy in optical, electrical, and defect properties. [20] The orientations of Sb 2 S 3 film could be controlled by substrate conditions and deposition techniques. [21,22] The Sb 2 S 3 film with [hk0] orientation means molecular chains are parallel to the substrate. The absorption capability of Sb 2 S 3 molecular chains changes along with the intersection (polarization) angle (θ) between light polarization direction and axis, which results in polarizationsensitive photo response. [23] The Sb 2 S 3 thin film PDs have large potential in polarized light detection.
Lead chalcogenide quantum dots (QDs) are one of the next generations of ideal narrow bandgap infrared semiconductors, due to their succinct solution processing, low‐cost fabrication, size‐tunable infrared bandgap, and excellent optoelectronic properties. Tremendous efforts including synthesis methods, surface ligand engineering, and device architecture engineering, drastically contribute to the significant improvement of the performance of the photodetectors based on QDs. In recent years, with the rapid development of consumer electronics, short‐wave infrared (SWIR) imaging sensors are in urgent demand. Thanks to the flexible manipulation of the QD thin film deposition process, a variety of QD‐based imaging technologies have been studied, including single‐pixel imaging sensors, integrated imaging sensors with readout circuit, and upconversion imaging sensors, which can effectively reduce the cost of SWIR imaging sensors and promote the commercial application in the consumer electronics. Herein, recent advances of QD‐based photodetectors and imaging sensors are summarized, emphatically focusing on the synthesis of QDs, surface ligand engineering, device architecture engineering, and imaging technology.
Real-time wavefront correction is a challenging problem to present for conventional adaptive optics systems. Here, we present an all-optical system to realize real-time wavefront correction. Using deep learning, the system, which contains only multiple transmissive diffractive layers, is trained to realize high-quality imaging for unknown, random, distorted wavefronts. Once physically fabricated, this passive optical system is physically positioned between the imaging lens and the image plane to all-optically correct unknown, new wavefronts whose wavefront errors are within the training range. Simulated experiments showed that the system designed for the on-axis field of view increases the average imaging Strehl Ratio from 0.32 to 0.94, and the other system intended for multiple fields of view increases the resolvable probability of binary stars from 30.5% to 69.5%. Results suggested that DAOS performed well when performing wavefront correction at the speed of light. The solution of real-time wavefront correction can be applied to other wavelengths and has great application potential in astronomical observation, laser communication, and other fields.
Curvature wavefront sensing usually requires the measurement of two defocused images at equal distances before and after the focus. In this paper, a new wavefront recovery algorithm based on only one defocused image is proposed. This algorithm contains the following four steps: response matrix calculation, establishment of intensity distribution equations, Zernike coefficients solution derived from the least squares method, and defocused image compensation with the solved Zernike coefficients. The performance of the algorithm in a large obscuration ratio and fast focal ratio optical system on axis and the edge of the field of view (FOV) is examined. Two optical systems of the Hubble telescope and a modified Paul-Baker telescope are employed to test the algorithm. The simulations show that the proposed algorithm outperforms in structural simplicity, and applications are expected in the wavefront recovery of the extreme environment (i.e., in space and the Antarctic).
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