Generation of pulsed squeezed light in a mode-locked optical parametric oscillator

The generation of pulsed squeezed light using an optical parametric oscillator (OPO) is discussed. This mode-locked optical parametric oscillator consists of a nonlinear crystal in a cavity which is resonant for both signal and idler waves and which is synchronously pumped by the second-harmonic of an acousto-optically mode-locked cw Nd: YAG laser. The fundamental wavelength of the pump laser provides local oscillator pulses for balanced homodyne detection of squeezed vacuum pulses emitted by the oscillator when operated below oscillation threshold. Photocurrent noise reduction to 30% below the classical shot-noise limit is observed, corresponding to squeezing of the field to a level approximately a factor of two below the mean square vacuum noise.     

Effects of roughness on the retroreflection from dielectric layers

The backscattering of electromagnetic radiation from rough dielectric layers with strong reflectors is studied both theoretically and experimentally. The retroreflected intensity is calculated as a function of the angle of incidence for different polarizations and different parameters of layers. It is shown that the interference pattern is extremely sensitive to the long-scale component of the roughness. The theoretical results are in a good agreement with the measurements of light scattering. The results are discussed in the context of microwave subsurface remote sensing.