A nanosecond gate-mode-driven silicon avalanche photodiode and its application to measuring fluorescence lifetimes of Ce-doped YAG ceramics

Abstract

We propose a silicon avalanche photodiode (Si-APD)-based boxcar-integrator, in which the Si-APD is driven in the gate mode. In the gate mode, by setting the direct current reverse-bias voltage Vr applied to the APD to below its breakdown voltage Vb, we superimpose a gate pulse of amplitude Vg on Vr so that the total voltage is nearly equal to Vb, but does not exceed it, i.e. Vr + Vg < Vb. In this case, the instantaneous current multiplication factor Mi of the APD is noticeably enhanced, especially when the duration of the gate pulse tw is reduced to the nanosecond scale. Because the gated Si-APD plays the role of a sampling unit as well as that of a photodetector for the repeatable signal light incident on the APD, in principle, the proposed scheme has an advantage in terms of the measured signal-to-noise ratio (SNR). To demonstrate the usefulness of the scheme, we have measured the fluorescence lifetimes of cerium-doped yttrium–aluminum–garnet (Ce:YAG) ceramics where the concentration of Ce is varied in steps.