Review on Speckle-Based Spectrum Analyzer

Wan, Yangyang; Fan, Xinyu; He, Zuyuan

doi:10.1007/s13320-021-0628-3

Cited by 21 publications

(10 citation statements)

References 80 publications

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“…Spectrometers, widely implemented in spectroscopic measurement, are facilitated by using speckle patterns 1 , 2 . The speckle pattern generated in disordered media is unique at each wavelength to reconstruct the input spectrum.…”

Section: Introductionmentioning

confidence: 99%

“…Spectrometers, widely implemented in spectroscopic measurement, are facilitated by using speckle patterns. 1,2 The speckle pattern generated in disordered media is unique at each wavelength to reconstruct the input spectrum. Random reflection, scattering, and interference generate speckle patterns during the propagation of light in multimode fiber, [3][4][5][6][7][8][9] singlemode fiber, 10,11 integrating sphere, 12 integrated waveguide, [13][14][15] or more disordered materials.…”

Section: Introductionmentioning

confidence: 99%

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Whispering-gallery-mode barcode-based broadband sub-femtometer-resolution spectroscopy with an electro-optic frequency comb

Xu,

Wan,

Fan

et al. 2024

Adv. Photon.

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.Spectroscopy is the basic tool for studying molecular physics and realizing biochemical sensing. However, it is challenging to realize sub-femtometer resolution spectroscopy over broad bandwidth. Broadband and high-resolution spectroscopy with calibrated optical frequency is demonstrated by bridging the fields of speckle pattern and electro-optic frequency comb. A wavemeter based on a whispering-gallery-mode barcode is proposed to link the frequencies of a probe continuous-wave laser and an ultrastable laser. The ultrafine electro-optic comb lines are generated from the probe laser to record spectrum of sample with sub-femtometer resolution. Measurement bandwidth is a thousandfold broader than comb bandwidth, by sequentially tuning the probe laser while its wavelength is determined. This approach fully exploits the advantages of two fields to realize 0.8-fm resolution with a fiber laser and 80-nm bandwidth with an external cavity diode laser. The spectroscopic measurements of an ultrahigh Q-factor cavity and gas molecular absorption are experimentally demonstrated. The compact system, predominantly constituted by few-gigahertz electronics and telecommunication components, shows enormous potential for practical spectroscopic applications.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Whispering-gallery-mode barcode-based broadband sub-femtometer-resolution spectroscopy with an electro-optic frequency comb

Xu,

Wan,

Fan

et al. 2024

Adv. Photon.

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“…[ 5 ] Speckles are recorded by launching incident lightwaves through a random medium that provides interferences of multiple reflections/refractions or gives variable spectral responses. [ 6 ] Inspired by this concept, random media such as single‐mode [ 7 ] or multi‐mode fibers, [ 8 ] integrating spheres, [ 9 ] and photonic crystal cavity array [ 10 ] have been used as the key element for RSA.…”

Section: Introductionmentioning

confidence: 99%

Reconstructive Spectrum Analyzer with High‐Resolution and Large‐Bandwidth Using Physical‐Model and Data‐Driven Model Combined Neural Network

Wan

Fan

et al. 2023

Laser & Photonics Reviews

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Most neural networks (NNs) used for reconstructive spectrum analyzers (RSAs) rely on data-driven training strategies, which can be time-consuming due to the need for a large training dataset with a limited amount of output channels. Here, a specially designed NN is proposed for a reconstructive wavemeter based on temporal speckle obtained from a whispering gallery mode (WGM) resonator. By combining a physical model and data-driven model, it only takes 10 µs to obtain a reference speckle for the generation of a training dataset. The WGM resonator-based wavemeter assisted by the NN uses only one photo-detector to obtain a temporal speckle, achieving a spectral resolution of 3.2 fm. The number of output channels reaches 2300, which is the largest dynamic range achieved by an NN in RSA without the need for re-training. It demonstrates that the proposed NN has capability to resolve unseen spectrum with multi-tone wavelengths. Moreover, the proposed network exhibits better robustness in long-time measurement compared to data-driven model based networks. This opens up new possibilities for NN design methods in RSA, without the need for a large training dataset, by incorporating a physical model to achieve high-resolution, high-dynamic-range, and fast-speed spectrum measurement.

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“…The same authors also used PCA to separate femtometer-resolved multiple independent wavelength measurements with a 0.2 fm precision from a 1 m long step-index MMF [ 24 ]. In recent years, PCA speckle pattern analysis has particularly yielded higher scales of wavelength resolution beyond the traditional methods mentioned earlier [ 25 , 26 , 27 ]. Hence, it is evident that the concept of speckle pattern analysis has led to a variety of breakthroughs in optical sensing for the development of fiber specklegram sensors (FSS), some of which have been applied to chemical sensing [ 28 ], force myography sensing [ 29 ], modal power distribution sensing [ 30 ], temperature and weight sensing [ 31 ], fluid properties sensing [ 32 ], and mechanical stimuli sensing [ 33 ].…”

Section: Introductionmentioning

confidence: 99%

A Machine Learning Specklegram Wavemeter (MaSWave) Based on a Short Section of Multimode Fiber as the Dispersive Element

Inalegwu

Gerald

Huang

2023

Sensors

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Wavemeters are very important for precise and accurate measurements of both pulses and continuous-wave optical sources. Conventional wavemeters employ gratings, prisms, and other wavelength-sensitive devices in their design. Here, we report a simple and low-cost wavemeter based on a section of multimode fiber (MMF). The concept is to correlate the multimodal interference pattern (i.e., speckle patterns or specklegrams) at the end face of an MMF with the wavelength of the input light source. Through a series of experiments, specklegrams from the end face of an MMF as captured by a CCD camera (acting as a low-cost interrogation unit) were analyzed using a convolutional neural network (CNN) model. The developed machine learning specklegram wavemeter (MaSWave) can accurately map specklegrams of wavelengths up to 1 pm resolution when employing a 0.1 m long MMF. Moreover, the CNN was trained with several categories of image datasets (from 10 nm to 1 pm wavelength shifts). In addition, analysis for different step-index and graded-index MMF types was carried out. The work shows how further robustness to the effects of environmental changes (mainly vibrations and temperature changes) can be achieved at the expense of decreased wavelength shift resolution, by employing a shorter length MMF section (e.g., 0.02 m long MMF). In summary, this work demonstrates how a machine learning model can be used for the analysis of specklegrams in the design of a wavemeter.

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Review on Speckle-Based Spectrum Analyzer

Cited by 21 publications

References 80 publications

Whispering-gallery-mode barcode-based broadband sub-femtometer-resolution spectroscopy with an electro-optic frequency comb

Whispering-gallery-mode barcode-based broadband sub-femtometer-resolution spectroscopy with an electro-optic frequency comb

Reconstructive Spectrum Analyzer with High‐Resolution and Large‐Bandwidth Using Physical‐Model and Data‐Driven Model Combined Neural Network

A Machine Learning Specklegram Wavemeter (MaSWave) Based on a Short Section of Multimode Fiber as the Dispersive Element

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