Periodic Reporting for period 1 - Brainiaqs (BRAIN IMAGING WITH ARRAYS OF QUANTUM SENSORS)
Periodo di rendicontazione: 2020-10-16 al 2022-01-15
The objectives are:
1) Develop a 100-pixel array of quantum sensors based on superconducting nanowire single-photon detectors, with >80% detection efficiency, <20 ps time resolution and <50 ns deadtime able to count single photons in the wavelength range 1000-2500 nm.
2) Develop a near-IR Multi-Photon Microscopy system specifically designed to operate with near-IR chromophores and implement the detector of objective (1). The system will allow for a detection area of 1 mm2.
3) Use the near-IR Multi-Photon Microscopy system to noninvasively image biological functions in a mouse brain at millimetre depth.
We design and fabricated arrays of superconducting quantum sensors organized in bins for spectroscopy and imaging achieving high efficiency (up to 90%), low dark counts (down to 10 cps) and an ultrahigh time resolution (<10 ps) both in the visible and near-infrared. So far we have shown that we can scale up the detectors to 24 pixels, with an active area of about 50x50 micrometer.
The readout electronics that sense and amplify the photon detection signal have a significant influence to the overall detector characteristics, such as timing jitter, reset times and maximum count rates. Cryogenic low-noise amplification of extremely weak SNSPD output signal can significantly improve the signal-to-noise-ratio, thereby minimizing timing jitter. We have designed and characterized the first low noise amplifiers based on SiGe for operation with SNSPDs.
To show the innovation potential of the newly developed instrument we have implemented the detectors in a first bioimaging experiment. This has been done in close collaboration with project partner EMBL in order to ensure a timely dissemination of our technology and to receive critical feedback that will allow us to further tailor the microscope’s performance parameters for utmost practicality and impact. The first proof of principle measurements have been performed.
So far, low noise amplifiers traditionally obtained with InP HEMT amplifiers. Recently, silicon SiGe HBT technologies have shown to obtain noise figures comparable to InP HEMTs7. The benefit of silicon technologies is their better integration capabilities that is essential for large arrays along with low power consumption and good performances in the DC-3GHz range where we need amplification. So far this type of amplifiers has never been used with sensors based on superconducting nanowires, however it is expected a design can be made that is suitable to amplify the signal of these type of sensors. For the bio-imaging application the detectors were compared to traditional detectors. Although not using them yet at the wavelength with the highest potential, a clear improvement in signal to noise ratio has been shown.