We demonstrate improved efficiency and dynamic range for two-photon absorption at 1.5 µm in a photoelectron-counting GaAs photomultiplier tube. cw laser measurements show pure two-photon absorption occurring in the device from average powers of 1.3 µW to nearly 1 mW. We use the detector to implement an autocorrelator with peak-power × average-power sensitivity of 1.7 × 10<sup>-4</sup> (mW)<sup>2</sup> and discuss practical ways to reduce this figure of merit to as low as 1 × 10<sup>-5</sup> (mW)<sup>2</sup>.
© 2002 Optical Society of America
Jeffrey M. Roth, T. E. Murphy, and Chris Xu, "Ultrasensitive and high-dynamic-range two-photon absorption in a GaAs photomultiplier tube," Opt. Lett. 27, 2076-2078 (2002)