Highly efficient quantum dense coding for continuous variables has been experimentally accomplished by means of exploiting a bright Einstein-Podolsky-Rosen (EPR) beam with anticorrelation of amplitude quadratures and correlation of phase quadratures. Two bits of classical information are encoded on two quadratures of a half of a bright EPR beam, then are simultaneously decoded by the other half of the EPR beam with the sensitivities beyond that of the shot noise limit. A high degree of immunity to unauthorized eavesdropping has been experimentally demonstrated.

A high energy long pulse and low peak power at 365nm ultra-violet laser is described. The laser at this wavelength is produced by the second harmonic generation of a flash-lamp pumped solid state Alexandrite laser. At optimum temperature, coherent 365nm light of 186mJ/pulse with 220 gs width is obtained without Q-switching.

A compact LD pumped intracavity frequency-doubled and frequency-stabilized ring Nd: YAP/KTP laser with high output up to 1.1W at 540nm is achieved. In the design of the laser configuration, the anisotropic characteristics of Nd:YAP optical biaxial crystal are taken into account. A quarter-wave plate is placed between the Faraday rotator and the s-cut KTP to ensure the output fundamental wave from KTP in pure linear-polarization paralleling to that of the oscillating laser and unidirectional operation of laser. Due to rigorously temperature controlling on KTP crystals and optimizing design of resonator, the stable single-frequency green output is obtained. The intensity fluctuation is less than + 1.5%, and frequency stability is better than

A frequency-doubled and frequency-stabilized ring Nd: YAP laser with a six-mirror cavity is demonstrated. This laser satisfies both the thermal insensitivity and optimal frequency-doubling conditions. A second-harmonic output to 1W at 0.54mm is achieved. The intensity fluctuation is less than 61.5% and the frequency stability is better than 61MHz

The configuration of a semimonolithic continuous wave nondegenerate optical parametric oscillator (cw-NOPO) consisting of an a-cut KTP crystal pumped by an intracavity frequency-doubled and frequency-stabilized Nd: YAP laser is reported. Both two-mode quadrature-phase squeezing of 3:7dB and intensity-difference squeezing of 7dB have been generated from the cw-NOPO operating respectively below and above the oscillation threshold through the frequency down-conversion process.