Theoretical discussion is given of low-noise uncooled parametric down-converter which is realized by using two unsynchronized pump generators at different frequencies.
In terms of a new Hamiltonian we introduce a modified Jaynes–Cummings model to represent the interaction between a two-level atom and two electromagnetic fields injected simultaneously within a perfect cavity. The field–field interaction is assumed to be in the frequency converter form. Exact expressions of the dynamical operators is given by solving the equations of the motion in the Heisenberg picture. The entropy squeezing is examined in the framework of Shannon information entropy. Using the entropic uncertainty relation, one can be able to show that there is a new kind of quantum squeezing in the entropy.
Quantum-correlated twin beams were successfully generated from an optical parametric oscillator (OPO) pumped by a frequency-doubled diode laser. The 50-mW diode laser output at 1080 nm was first converted to 22.5-mW green light, and then was used to pump an OPO to yield signal and idler beams with a total power of 5 mW. Noise reduction of 4.3 dB below the shot-noise level was observed in the intensity-difference spectrum. The setup opens a simple way to a compact and low-cost source of diverse nonclassical states of light.