关键词:
Automatic testing
摘要:
Objective The characterization of single-photon detectors (SPDs) plays an important role in the development and application stages of SPDs. The demand grows as the application of solid-state SPDs rapidly increases in fields such as LiDAR and low-light imaging. Since SPDs typically respond to incident photons over a wide spectral range, measurement of the photon detection efficiency (PDE) of an SPD over its entire spectral response range (i.e., PDE spectrum) becomes a complex and time-consuming task. Traditionally, the correlated-photon method and the standard detector substitution (SDS) method are commonly used for the measurement of PDEs of SPDs. However, these methods require additional measurements and corrections for the dead time, afterpulsing, and dark count effects to obtain an accurate PDE. This limitation can be overcome using our recently proposed event-refreshed time-to-digital converter (ER-TDC)-based method. In this study, we design and develop an automatic PDE spectrum testing system based on ER-TDC to improve measurement efficiency and repeatability, and its performance is fully tested. Methods A dedicated system, consisting of a light-emitting diode (LED) array and an ER-TDC, is designed and developed for measuring PDE spectra (400 ‒ 1100 nm) of SPDs [Fig. 2(a)], with the supporting automatic measurement procedure (Fig. 4) implemented in Python. The spectral and temporal emission characteristics of the LEDs at different powers (1.0 ‒ 800.0 nW) are measured using a fiber optic spectrometer and ER-TDC, respectively. Power calibration measurements are conducted on the automatic system exploiting two calibrated photodiodes (PDs). The performance of the automatic system is tested at various LED emitting powers using a commercially available silicon single-photon avalanche diode (Si-SPAD), and the resulting PDE spectrum is compared with that measured by the traditional SDS method [Fig. 2(b)]. Results and Discussions The central wavelength (Fig. 5) and powe