Fig. 1. Experimental setup for generation and measurement of squeezed vacuum state of femtosecond pulse

Fig. 2. Relationship between femtosecond pulse vacuum squeeze and sweeping time. (a) Instantaneous state; (b) long-term sampling result

Fig. 3. Local and pump phase-locked loop experimental setup

Fig. 4. Error signal

Fig. 5. Relationship between femtosecond pulse vacuum squeeze and sweeping time under lock condition

Fig. 6. Long-term sampling result

Fig. 7. Comparison of long time drifts at squeeze positions

Fig. 8. Squeezed noise curves after multiple averages. (a) Unlocked condition; (b) lock condition