Recently, a research team from the National Key Laboratory of Optical Quantum Technology and Devices at Shanxi University utilized a new scheme of reservoir-engineered parametric coupling to experimentally realize a novel squeezed laser light source. The relevant research findings, titled "Reservoir-engineered squeezed lasing through the parametric coupling," were published in the top physics journal Physical Review Letters.
Figure 1. Schematic diagram of the principle of squeezed lasing
Compared to squeezed light fields, squeezed lasers combine the coherence of classical lasers with the quantum properties of squeezed vacuum fields, offering potential applications in quantum optics and broader fields of physics. However, the superior coherence of lasers is a product of the strong interaction between stimulated emission and light amplification, and during the process of stimulating particles for stimulated emission, quantum properties are destroyed; The preparation of compressed light fields relies on spontaneous emission processes, which maintain quantum correlations through phase-sensitive manipulation of weak interactions. However, this process degrades the coherence of the output light field. Therefore, existing laser excitation and compressed state preparation schemes cannot achieve the unity of light field coherence and quantum properties, posing significant challenges for the experimental preparation of compressed lasers.
Figure 2. Experimental test results demonstrating the unity of laser and compressed properties
This study, based on our group's high-compression-degree compressed-state optical field preparation technology, employs a technical scheme utilizing vacuum editing in optical parametric coupling to address the challenge of reconciling laser coherence with compressed-state quantum properties. It successfully prepares a novel quantum resource of high-power, narrow-linewidth, high-compression-degree compressed lasers for the first time experimentally. Specifically: A theoretical model for the evolution of compressed laser noise was established, and a novel technical scheme for preparing compressed lasers using vacuum-edited optical parametric coupling was proposed. Low-loss, phase-change-free optical parametric oscillators, strong parametric coupling, and single-mode selection techniques were developed, enabling the experimental preparation of compressed lasers with a maximum compression degree of -6.1 dB, a linewidth of 15 kHz (approaching the initial laser linewidth), and an output power of 2.6 mW. This work has demonstrated for the first time the phase transition process in a compressed-state suppression cavity enhancement system, achieved effective preservation of quantum states in a strong parametric coupling system, and expanded the application of compressed states in actual physical systems.
