Long-term stable bright amplitude-squeezed state of light at 1064 nm for quantum imaging

Bright amplitude-squeezed light at 1064 nm is generated with excellent long-term stability by utilizing the degenerate optical parametric amplifier (OPA) based on periodically poled KTiOPO4 (PPKTP) crystal. Amplitude noise reduction of as much as −5.5 dB is observed directly at an output power of 0.3 mW. This corresponds to a squeezing of −6.22 dB in the beam, the detection efficiency and the propagation efficiency are taken into account. The average value of the detected noise reduction in continuous operation over 5 h is −3.8 dB by locking the cavity length of the OPA. The squeezed state light is applied for imaging of virtual object. The experimental results indicate that the obtained image is more distinct and has less distortion compared to that obtained by infrared coherent light.