Research On High Frequency Noise In Laser Pulse Signal Of Q-switched DPL

This paper deeply research and improve the optical detecting circuit with a capacitive bias voltage ,that could collect the high frequency noise in the laser pulse signal with the 1ns response-time AEPX65 PIN photodiode and Tektronix TDS5000B high speed sampling oscilloscope(Fast frame function). This high frequency noise in the laser pulse signal not only behaves the signal's amplitude and pulse width unstable which makes the different field distribution but also affect the pulse's stability of establish time. By the conversion from time to frequency, the high frequency noisy signal is mainly made of two parts in the frequency domain: The first part signal of 0.25GHZ～1GHZ and the second part signal of 1GHZ～1.8GHZ.After the comparison with the result of emulate data, it conclude that the first part signal is mainly affected by the laser multi-longitudinal mode distribution which is the main cause of the pulse width's instability in field distribution. The second part signal of 1GHZ～1.8GHZ is mainly affected by the laser multi-transverse mode distribution ,that is the main fact of the amplitude and pulse width's instability.