  The heightened sensitivity observed in non-Hermitian systems at exceptional
points (EPs) has garnered significant attention. Typical EP sensor
implementations rely on precise measurements of spectra and importantly, for
real time sensing measurements, the EP condition ceases to hold as the
perturbation increases over time, thereby preventing the use of high
sensitivity at the EP point. In this work, we present an new approach to EP
sensing which goes beyond these two traditional constraints. Firstly, instead
of measuring the spectra, our scheme of EP based sensing is based on the
observation of decay length of the optical mode in finite size gratings, which
is validated via coupled mode theory as well as full wave electrodynamic
simulations. Secondly, for larger perturbation strengths, the EP is spectrally
shifted instead of being destroyed -- this spectral shift of the EP is
calibrated and using this look-up table, we propose continuous real time
detection by varying the excitation laser wavelength. As a proof of principle
of our technique, we present an application to the sensing of coronavirus
particles, which shows unprecedented limit of detection. These findings will
contribute to the expanding field of exceptional point based sensing
technologies for real time applications beyond spectral measurements.
