Detection of stably bright squeezed light with the quantum noise reduction of 126  dB by mutually compensating the phase fluctuations

Abstract

We present a mutual compensation scheme of three phase fluctuations, originating from the residual amplitude modulation (RAM) in the phase modulation process, in the bright squeezed light generation system. The influence of the RAM on each locking loop is harmonized by using one electro-optic modulator (EOM), and the direction of the phase fluctuation is manipulated by positioning the photodetector (PD) that extracts the error signal before or after the optical parametric amplifier (OPA). Therefore a bright squeezed light with non-classical noise reduction of π is obtained. By fitting the squeezing and antisqueezing measurement results, we confirm that the total phase fluctuation of the system is around 3.1 mrad. The fluctuation of the noise suppression is 0.2 dB for 3 h.

Dependence of the squeezing and anti-squeezing factors of bright squeezed light on the seed beam power and pump beam noise

“…Since the first experimental demonstration of squeezed states based on the OPO succeeded in 1986 [16], intensive researches are carried out to increase the squeezing factor in the last thirty years [17][18][19][20][21][22][23][24][25][26]. Under the motivation of gravitational waves detection, a 10 dB squeezed vacuum state was detected for the first time at the University of Hanover in 2007 [20].…”

“…Our OPA is a semi-monolithic cavity consisting of a piezo actuated concave mirror and a PPKTP crystal and its parameters are the same as that of Ref. [23]. In order to ensure the results are taken, no experimental parameters other than the seed beam power and pump beam intensity and phase noise are varied during the measurement cycle.…”

“…During measurement of bright squeezed states, all data is taken under the conditions that the OPA cavity length and relative phase is actively controlled by using the mutual-compensation scheme [23]. The phase modulation signal is imprinted on the seed beam to generate error signal for all three control loops [31,32]: the error signal for stabilizing the OPA cavity length on resonance is demodulated from the photodetector PD2 placed in the reflected end of the OPA; the error signal of locking the relative phase between the pump and signal beams is obtain from the photodetector PD3 output.…”

Detection of 13.8 dB squeezed vacuum states by optimizing the interference efficiency and gain of balanced homodyne detection

“…In ideal conditions, an infinite squeezing factor can be generated and detected at the threshold. However, the measured squeezing level is usually limited by photon loss during squeezed states generation, propagation, and detection [12,[28][29][30] . The loss that occurs during the generation of the squeezed state is dependent of the escape efficiency of the OPO.…”

Detection and perfect fitting of 132 dB squeezed vacuum states by considering green-light-induced infrared absorption

“…The loss dependence becomes acute as the squeezing factor increases. In addition, the amount of squeezing generated has only a square-root dependence on the pump power [22,34]; the increase of pump power for a high squeezing factor induces higher GLIIRA loss in comparison with the status of a low squeezing factor. In order to detect a high-level squeezed state, it becomes urgent to consider and quantify the influence of GLIIRA loss on the squeezing factor in terms of an actual crystal sample.…”