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Favorable isolation performance in optical transmitting-receiving (T/R) channels is key to establishing full-duplex bi-directional laser communication links when designing mono-wavelength laser communication terminals. This study proposes a novel design scheme for T/R channels that use a single laser wavelength. The system includes measures such as the deflection at λ/4 wave plate angles, light trap installation at a polarization beam splitter, and removal of polarization analyzers in optimized systems. A mathematical model describing isolation in the optical T/R channels is presented. Three types of factors that affect the isolation of optical T/R channels were analyzed and simulated in detail. The present simulation results show that the roughness of the λ/4 wave plate and the solid angle of the detector field of view are exponentially related to T/R isolation, which can thus be regarded as the most significant factors affecting isolation. According to the present design scheme, the prototype T/R channel was developed for measuring isolation. The measured value (77.8 dB) agrees well with the result determined using the established mathmatical model (77.3 dB). Conclusively, the present theoretical model can provideguidance for optimizing isolation in a mono-wavelength optical channel. Thus, it can be applied extensively in laser communication systems, including inter-satellite networks.

Based on the extended Huygens-Fresnel principle, the cross-spectral density function of a chirped Gaussian pulsed beam propagating in slant atmosphere path was derived, and the spectra shift properties of chirped Gaussian pulsed beam in slant atmosphere path were studied. The results show that the on-axis spectral shifts may be red shift comparing to the spectra at the source plane L = 0, while the off-axis spectra shifts is blue shift. The results also show that the red shift or the blue shift of chirped Gaussian pulsed beam in slant atmosphere path will increase as the parameters C 0 and α of slant atmosphere increase.

The equations of anomalous hollow beam (AHB) in slant atmosphere have been derived, and the average intensity distributions have been illustrated and analyzed using numerical examples. The results shown that the AHB propagating in slant atmosphere will lose the initial dark hollow with a solid core profile and evolve into Gaussian beam as the propagation distance increases. The results also shown the AHB propagating in slant atmosphere with larger strength (larger C 0 or small zenith angle α ) will lose the initial beam profile faster at the same propagation distance L.

The equations of average intensity and beam widths of a four-petal Lorentz-Gauss vortex (FPLGV) beam propagating in turbulent atmosphere have been derived, and the evolutions of average intensity and beam widths of a FPLGV beam in turbulent atmosphere are discussed using numerical examples. It is found that intensity distribution of a FPLGV beam at the short distance can be controlled by modulating topological charge M and beam order N , and the FPLGV beam will translate into Gaussian beam due to the actions of atmospheric turbulence at longer distance. It is also found that the beam widths of a FPLGV beam will increase as the distance increases, and the beam propagating in stronger atmospheric turbulence will have a larger beam width at the same propagation distance.

Based on the extended Huygens-Fresnel integral, the analytical expression of average intensity of a rectangular multi-Gaussian Schell-model vortex (RMGSMV) beam propagating in turbulent atmosphere is derived, the effects of turbulent atmosphere on the average intensity and effective beam widths of a RMGSMV beam are analyzed. The numerical results indicate that the RMGSMV beam propagating in turbulent atmosphere will gradually evolve from the dark hollow beam into a solid beam with Gaussian-like distribution, and the effective beam width W x z of a RMGSMV beam propagating in turbulent atmosphere with larger C n 2 will have a larger beam width. The results also show that the effective beam width of a RMGSMV beam with smaller σ , larger M and N 1 = N 2 will have a larger effective beam width as the propagation distance increases.

Considering the theory of coherence, the rectangular multi-Gaussian Schell-model vortex beam (RMGSMV) beam generated by multi-Gaussian Schell-model source has been introduced, and the propagation properties of RMGSMV beam propagating in free space has been analyzed by using the derived equations. The effects of beam parameters on the properties of RMGSMV beam propagating in free space have been discussed. The results show that the RMGSMV beam propagating in free space can remain the dark hollow center at the short propagation distance, and the beam will gradually evolve into a beam with similar rectangular flat-topped profile as the propagation distance increases.

Starting from Maxwell's equations and considering the quadratic electro-optic effect as a perturbation, we present a generalized wave coupling theory of quadratic electro-optic effect in linear absorbent centrosymmetric medium. We use a KLTN crystal as an example for studying the influences of linear absorption on the amplitudes and phases of the two electromagnetic wave components of electro-optic modulation.