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Semi-Dispos.png

Fig. 1. Pixel devices made from
metal/YBCO semiconductor/metal trilayers
(C2N clean-rooms, Paris Saclay University).

Semi-Caracs_2.png

Fig. 2. For a trilayer device, current response (blue) and analytic model (red).

 A. Cheneau, DOI: 10.1109/IRMMW-THz50927.2022.9895502

Semi-Antenna.png

Fig. 3. Chicken-leg antenna coupled pixel device (C2N clean-rooms, Paris-Saclay University).

Room temperature terahertz 2D thermal imaging arrays

 

 

Context

Low power terahertz waves are fully harmless electromagnetic waves in the frequency range from 500 to 5000 GHz (= 5 THz). These waves can penetrate dielectric or non-conducting materials like plastics, ceramics, paper, wood, fabric, etc. By contrast, metallic or conducting surfaces are reflecting those waves.

THz imaging is therefore a promising technique in various applications: environment domain, health domain (blood circulation, tumour detection), fusion plasma imaging (renewable energy), industry (temperature control, hostile media), civil security (suspect objects concealed underneath clothing)...

Materials science and device aspects

We are developing pyroelectric detectors made from semiconducting Y-Ba-Cu-O (hereafter YBCO) oxide materials (Fig.1). These semiconductor oxides can be prepared at room temperature in the form of thin films and can be integrated with already processed CMOS electronic readout technologies. Near infrared (IR) tests (at 0.850 µm wavelength) of detectors made from these films show impressive performance (see Fig. 2) in terms of low noise and time constant (< 20 ns) as compared to commercial pyroelectric detectors (0.1-100 ms). We are now developping these detectors for longer wavelengths (THz waves).

Electromagnetic coupling and thermal budget aspects

 

These concern first the implementation of micro-antennas associated with the elementary pixels, so to optimize the electromagnetic coupling between the incoming radiation and the sensing element. The specificity here is to accommodate the large pixel impedance (several kW) while maintaining a large bandwidth (1 to 4 THz, typically), which leads to non-standard antenna structures (Fig. 3).

To cope with thermal aspects (bolometer sensitivity, crosstalk between pixels), modelling is performed to design pixel arrays with optimized surface density.

 

Readout electronics aspect

This deals with the design, realization and test of readout and signal processing circuitry associated with the pixel array, currently in CMOS technologies. In particular, low noise, high gain and large bandwidth amplifiers are required.

Optical engineering aspect

As an initial step, it concerns the design of detector optical characterization setups, from the near infrared to the far infrared. In view of a direct detection active imaging system design, the main concerns are the scene illumination with a scanned THz source and the associated focusing optics, to reach a compromise between pixel sensitivity, array size and frame rate.

Some related publications

  1. A. Cheneau, A. Dégardin, and A. Kreisler, “Mixed oxide provides an efficient solution to near infrared detection,” Proc. SPIE 12737, Electro-Optical and Infrared Systems: Technology and Applications XX, 1273704 (2023). doi: 10.1117/12.2680357.

  2. A F. Dégardin, V.S. Jagtap, and A. J. Kreisler, "Semiconducting amorphous Y-Ba-Cu-O: an attractive material for fast and sensitive thermal sensing in the NIR to THz range," Proc. SPIE 11279, pp. 1127909-1/12 (2020).

  3. A. Dégardin, V. Jagtap, M. Razanoelina, X. Galiano, M. Tonouchi, A. Kreisler, “Y-Ba-Cu-O semiconducting pyroelectric thermal sensors: design and test of near-infrared amorphous thin film detectors and extension to antenna-coupled THz devices,” SPIE Proc. 11164, pp. 1116409-1/13 (2019).

  4. M. Razanoelina, S. Ohashi, I. Kawayama, H. Murakami, A. F. Dégardin, A. J. Kreisler, and M. Tonouchi “Measurable lower limit of thin film conductivity with parallel plate waveguide terahertz time domain spectroscopy,” Optics Letters 42 (15), pp. 3056-3059 (2017).

  5. A.J. Kreisler, A.F. Dégardin, X. Galiano & D. Alamargui, “Low noise and fast response of IR sensing structures based on amorphous Y-Ba-Cu-O semiconducting thin films sputtered on silicon,” Thin Solid Films 617, pp. 71-75 (2016).

  6.  A.F. Dégardin, V.S. Jagtap, X. Galiano & A.J. Kreisler, “Semiconducting Y-Ba-Cu-O thin films sputtered on MgO and SiOx/Si substrates: Morphological, electrical and optical properties for infrared sensing applications,” Thin Solid Films 601, pp. 93-98 (2016).

  7. X. Galiano, A.F. Dégardin, V.S. Jagtap, A.J. Kreisler, "Fast pyroelectric response of semiconducting Y-Ba-Cu-O detectors with high IR sensitivity," IEEE Proceedings. DOI: 10.1109/IRMMW-THz.2015.7327488

  8. A.F. Dégardin, X. Galiano, A. Gensbittel, O. Dubrunfaut, V.S. Jagtap & A.J. Kreisler, "Amorphous Y–Ba–Cu–O oxide thin films: Structural, electrical and dielectric properties correlated with uncooled infrared pyroelectric detection performances," Thin Solid Films 553, pp. 104-108 (2014).

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