In this work, we present the recent results of designing and developing a miniaturized mid-IR spectrometer designed to detect and identify specific markers, which may provide crucial information on air/water/food quality, human health, production line condition, etc.
The device is designed to operate in the spectral range of 3–5 µm or 7–9 µm, depending on the detector used, with a spectral resolution of approx. 20–100 nm, chosen appropriately for the targeted applications. Specific focus has been placed on the potential for the further miniaturization and cost optimization of the device.
The heart of the spectrometer, determining its spectral selectivity, is a 32-element, thermoelectrically cooled linear detector array (LDA) and a linear-variable filter (LVF). The LDA consists of InAsSb photodiodes, which, for a temperature of 230 K, offer a specific detectivity D* of the order of 1010/108 cmHz−1/2W−1 for the spectral range of 3–5 µm and 7–9 µm, respectively. The LVF’s spectral response changes linearly along its length—since it is placed parallelly and near the LDA, this effectively restricts the spectral response of each pixel to a narrow peak, shifted by a constant value with regard to its neighbors.
To test the applicability of the device, a standalone demonstrator was developed, consisting of a thermal light source, beam-forming optics, a light beam modulator and an optoelectronic detection setup. To prove the proper operation of this device, several tests were performed, evaluating, among other aspects, its detection limits for different substances. Various measurement configurations (transmissive, reflective, and multi-pass) were tested to improve the flexibility of the developed solution.
Since the presented work is a part of a bigger project focusing on the development of fully integrated micro-spectrometers, the perspectives for further miniaturization will also be discussed, with specific focus placed on the potential of photonic integrated circuits (PICs).
Author Contributions
Conceptualization, F.Ł., P.L. and J.K.; methodology, F.Ł., A.G. and D.S.; software, F.Ł.; validation, F.Ł. and J.K.; formal analysis, F.Ł.; investigation, F.Ł. and J.K.; resources, A.G. and D.S.; data curation, F.Ł.; writing—original draft preparation, F.Ł.; writing—review and editing, J.K. and R.P.; visualization, F.Ł.; supervision, P.L. and R.P.; project administration, P.L. and R.P.; funding acquisition, P.L. and R.P. All authors have read and agreed to the published version of the manuscript.
Funding
This work was supported by the National Centre for Research and Development project MIRPIC (TECHMATSTRATEG-III/0026/2019).
Institutional Review Board Statement
Not applicable.
Informed Consent Statement
Not applicable.
Data Availability Statement
The data that support the findings of this study are available from the corresponding author, F.Ł., upon reasonable request.
Conflicts of Interest
The authors declare no conflict of interest.
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