Two-Color Quantum Correlation between Down-Conversion Beams at 1.5 and 3.3 μm from a Singly Resonant Optical Parametric Oscillator

Abstract

We demonstrated a two-color quantum correlation between the down-conversion beams with a telecommunication wavelength at 1.5 μm and mid-infrared wavelength at 3.3 μm generated by a singly resonant optical parametric oscillator (SRO) operated above the pump threshold with a magnesium-oxide doped periodically-poled lithium niobate crystal in the cavity. A maximum of 1.8 dB noise reduction of the intensity difference of the twin beams was measured at the analysis frequency of 5 MHz. Based on a theoretical model for the quantum correlation between the twin beams given by a semi-classical approach, the influence of the analysis frequency and pump parameter on the quantum correlation between the twin beams was discussed theoretically and experimentally. The quantum correlation between the twin beams was degraded at the analysis frequencies above 5 MHz due to the limitation of the bandwidth of SRO cavity and was degraded at the analysis frequencies below 5 MHz due to the excess intensity noise of the pump. The two-color quantum correlated twin beams at 1.5 and 3.3 μm have potential applications in high-precision measurements beyond the shot noise level.

Single-frequency optical parametric oscillator intracavity-pumped by a visible VECSEL for low-noise down-conversion to 1.55 µm

“…As well as a reduction in quantum phase noise, ultra-narrow fundamental linewidths can also be reached, with sub-kHz linewidths having already been recently demonstrated within our research group [17,42,43], where identical AlGaInP-based VECSEL samples were utilized. While the degree of intensitydifference squeezing that can be achieved should be irrespective of the quantum phase noise and narrow linewidth operation of the OPO pump source, for a given low intensity noise, reducing these characteristics can still open up new possibilities and applications in e.g., atomic clocks [44], and quantum communication [45], cryptography [46], spectroscopy [47,48] and computing [49].…”