Accurate measurement of high extinction ratios of ultrafast pulsed sources

We present a technique to accurately measure the extinction ratio (ER) of pulses shorter than 10 ps and show that this technique is accurate for ER values from 20 to 50 dB. The technique is based on second-harmonic generation frequency-resolved optical gating. The ER of 1.8-ps pulses was measured and compared with a calculated value. The error between experimentally obtained value and the expected value is within 0.5 dB.