Study On Locking Techniques In Preparation And Detection Of Squeezed States Of Light

As an important non-classical resource, squeezed light has been widely adoptedin various fields. A lot of methods could be employed to generate squeezed states oflight, while the Optical Parametric Oscillator(OPO) is one of the most effectivemethods. However, the OPO cavity could be affected by external environmentaldisturbance, such as vibration and airflow, which will decrease significantly thesqueezing degree in the preparation of squeezed states of light. Therefore, somemethods must be conducted to stabilize the OPO cavity. The main results andinnovation of this paper are summarized as follows:First of all, we discuss theoretically the feasibility of preparation of squeezedstates of light by OPO cavity theoretically. We show that the bright quadratureamplitude squeezed states of light could be produced with periodically poledKTiOPO4(PPKTP) crystal by Quasi-phase matching in an OPO cavity.Secondly, we compare three different locking techniques which are the mostwidely employed: Pound-Drever-Hall (PDH) locking technique, dither lockingtechnique, and fringe locking technique. The comparison results show that the fringelocking technique could be adopted in the stabilization of the OPO cavity, since it ismore simple than other locking techniques, also, the fringe locking technique couldavoid additional noise caused by modulation of signal light. Furthermore, thesynchronous phase sensitive detection using a lock-in amplifier is not required in thefringe locking technique. Another advantage is that the squeezed light stabilized bythis technique doesn’t contain modulation signal, which is very important for theapplication of the squeezed light without modulation signal. In a word, the fringelocking technique could be employed in the preparation of squeezed states of light.Finally, experiments of stabilizing the OPO cavity by the fringe locking techniqueare performed. The experimental results show that the length variance of the cavity isfixed7.27nm over2hours in continuous operation, and the longest locking durationcan be up to3.8hours, which is sufficient for the detection of the squeezed states of light in the common experiments.