Signal recovery of a Fabry–Pérot interferometric x-ray pulse detector based on the RadOptic effect

Abstract

The signal recovery of a Fabry–Pérot interferometric x-ray pulse detector based on the RadOptic effect in the non-limiting case was investigated in this research. A Fe-doped InP with an invariant excess carrier recombination mechanism was used as the interference cavity material to achieve a constant temporal instrumental response function (tIRF). A linear and time-invariant detection system described by the convolution of the time-varying x-ray pulse and the constant tIRF was established based on the transient refractive index variation model determined by the three effects of band filling, band shrinkage, and free-carrier absorption. For the non-limiting case, the accumulation of excess carriers enhanced the sensitivity but altered the fluctuations of the real x-ray pulse. To realistically reconstruct the x-ray pulse, two-photon absorption of the infrared ultrashort pulse was used to simulate the ultrashort x-ray excitation to obtain the tIRF. Finally, using the conjugate gradient method, the original signal recorded by the detection system was deconvoluted to recover the signal. The success of signal recovery in the non-limiting case provided the basis for the development of detectors with adjustable sensitivity controlled by carrier lifetime.