INFORMATION TECHNOLOGY

Reconfigurable photonic technology enables large-bandwidth, picometer-scale on-chip spectrometers


A team from Optical Technology and the University of Cambridge proposed and implemented an on-chip integrated spectrometer scheme based on reconfigurable photonic technology, which realized ultra-high resolution in the picometer range and working bandwidth in the 100-nanometer range. In addition, the scheme exhibits excellent detection sensitivity, scalability, programmability, and thermal stability. This breakthrough opens up a new technology path for the miniaturization and practical application of high-performance spectrometers. At present, Guangyi Technology has completed the modular packaging applied to wearable products, so as to realize a wide range of spectroscopic applications such as physiological health and motion monitoring.

The article, published in the journal Light: Science & Applications, is titled “Broadband picometer-scale resolution on-chip spectrometer with reconfigurable photonics,” with Chunhui Yao as the first author and Qixiang Cheng as the corresponding author.

Spectrometers play an important role in many fields, including chemical analysis, biosensing, and materials characterization. In recent years, with the rapid development of mobile Internet of Things, the market has an increasing demand for small-size, low-cost, high-performance spectral analysis devices, such as health monitoring based on wearable devices, food safety monitoring and environmental monitoring based on handheld devices, and remote sensing imaging based on drones. However, traditional benchtop spectrometers are often constructed from large and expensive dispersive elements, which cannot meet the urgent need for real-time, convenient and accurate spectral analysis in modern society. Although academia and industry have been working to develop miniature spectrometers, shrinking in size often results in performance losses in terms of resolution, bandwidth, and signal-to-noise ratio. In recent years, computational spectrometers based on spectral time, spatial coding and numerical reconstruction algorithms have received extensive attention in the industry, but the currently reported technical solutions cannot overcome the technical problems of limited number of sampling channels or excessive coherence between sampling channels.

In order to break through the above technical bottlenecks, the team introduced the concept of reconfigurable photonic chips into spectral sampling shaping, and used reconfigurable photonic networks and distributed broadspectrum filtering technology to break through the size limitation of chip-level spectrometers and achieve picometer-level ultra-high resolution. Figure 1 shows a conceptual schematic of the proposed device, in which each node in the reconfigurable network is deployed with a broad-spectrum filtering element with different filtering portability, thereby assigning a nearly random filtering sampling response to different transmission paths.

Figure 1: Schematic diagram of the device architecture

By cleverly designing the spectral characteristics of each distributed filter element, the resulting quasi-random response has the characteristics of small autocorrelation and cross-correlation, so that the information of the entire spectrum can be efficiently extracted. At the same time, thanks to the scalability of the reconfigurable network, the exponential multiplication of sampling channels can be easily achieved. Figure 2 shows the on-chip spectrometer based on a 7-stage reconfigurable network integrated with the silicon nitride platform implemented by this work, and the resulting near-random spectral response of 256 sampling channels.

Figure 2: (a) Microscopic diagram of the spectrometer chip used in the experiment (b) The autocorrelation coefficient and correlation coefficient of the measured channel transmission response and the channel response of several channels (c-d) used as an example

Experiments show that the device has an operating bandwidth of more than 115 nanometers and a super-resolution of less than 30 picometers. Figure 3 shows the measurement results of detecting unimodal and bimodal narrowband laser signals and broadband ASE spectral signals, respectively, showing high reduction accuracy. Further simulation results show that by optimizing the number of sampling channels in the reconstructed network, the device can achieve single-digit picometer resolution, which meets or even exceeds the performance standards of many benchtop spectrometers.

Figure 3: (a) Reconstruction results of multiple narrowband laser signals (b) Reconstruction results of bimodal laser signals with different spacing (c) Reconstruction results of different broadband signals: ASE spontaneous spectrum for SOA (left) and ASE spontaneous spectrum for EDFA (right).

In addition, thanks to the low insertion loss of the reconfigurable photonic network and the low thermal sensitivity of the silicon nitride platform, combined with the simple control of the reconfigurable network, the device has strong practicability and universality.

Exhibition

The ultra-high-performance on-chip spectrometer presented in this article is expected to bring more innovative solutions to spectral analysis and related applications, including biomedical sensing, industrial chemical monitoring, and miniature optical imaging systems. At present, Guangyin Technology has completed the prototype development of the miniature spectral sensing module, as shown in Figure 4, the prototype product combines the spectrometer chip with artificial intelligence analysis algorithm, which is expected to quickly achieve a major commercial breakthrough in the field of sports health monitoring. (Source: China Optics)

Figure 4 Physical diagram of the wearable spectral sensing prototype of Guangyin Technology

Related paper information:https://doi.org/10.1038/s41377-023-01195-2

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