Theoretical And Experimental Investigation For The Generation Of Squeezed State Field At 1.5 μm With Quasi-phase Matching Crystal

In quantum information science, the ideal quantum information network system used light as the carrier of transmission and used atom as the node of storage. Since the wavelength of 1.5 μm corresponding to the minimum loss window and low dispersion window, the non-classical light at this wavelength had important applications in the optical fiber communication system based on fiber-optic transmission and also attracted many researchers all over the world threw themselves into this research. It was expected that the high-quality non-classical light field could be produced. The light could transmit in the low loss fiber over long distances when loading with information. During this process, the quantum property could be kept and quantum information could be effectively processed in order to promote the development of quantum information technology and the establishment of quantum information system. A high-quality entanglement was in need during these works. In my thesis for master degree, our group investigated on the generation of squeezed light at 1.5 μm from theoretical and experimental aspects. The main completed work was as follows:(1) A high power continuous wave (CW) single frequency 1.5 μm laser was experimentally generated. Two mode cleaners (MC) were used to filter the intensity noise of 1.5 μm laser and both of their transmission efficiencies were 80%. The intensity noise reached the shot noise limit (SNL) at the analysis frequency of 3 MHz for S polarization. This source provided the fundamental light of frequency-doubling process and the local light of balanced homodyne detection process.(2) A low noise high power CW single frequency 780 nm laser was obtained by external cavity frequency-doubling process and the conversion efficiency was 84.8%. The 780 nm laser was used as pump source of the optical parametric oscillator (OPO) and the crystal was periodically poled lithium niobate (PPLN) crystal. The maximum second harmonic (SH) output was 1W. In order to meet the low noise requirements of pump light of OPO, a 780 nm MC was used to filter the intensity noise of 780 nm laser. The intensity noise of 780 nm laser after the MC reached SNL at the analysis frequency of 4MHz for S polarization. The transmission efficiency of 780 nm MC was 80% and the maximum transmission SH power of MC was 700 mW.(3) A continuous variable (CV) squeezed vacuum at 1.5 μm was experimentally generated by using optical parametric process based on quasi-phase-matched crystal. We analyzed the factors affecting the degree of squeezed light field generated by OPO bellow threshold. The 780 nm high power CW single frequency low-noise laser produced before was used as the pump light of the OPO and 3 dB squeezed vacuum light at 1.5 μm was obtained.