The design of a combined functional phase-only diffractive optical element, which can be utilized in intersatellite optical communication, is demonstrated. The adopted design method of this paper is based on the nonlinear phase transformation by the law of colour separation, Rayleigth-Sommerfield diffraction theory, direct search optimization method, and Genetic algorithm. This combined functional phase-only diffractive optical element (CPDOE) is motivated by the intersatellite optical communication (IOC). To simplify the structure of optical systems in IOC, the PDOE combined two different functions into the same one element. The two functions are the colour separation and spatial focusing of beacon laser and signal laser. With the utilization of this element the structure of IOC can be highly simplified and integrated. The motivation of being used in IOC also raises the demands of large numerical aperture, polarization insensitivity and high diffraction efficiency. In order to predict the large angle diffraction precisely, the diffraction between the back side of DOE and focusing plane is computed by the means of Rayleigth-Sommerfield (RS) diffraction theory, a more rigorous diffraction theory than Fresnel diffraction theory. To get a high performance of optimization, the direct search and Genetic algorithm has been adopted, and the initial phase value has also be synthesized by the nonlinear phase transform by law of colour separation. The presented design result showed a high performance of the CPDOE. The high performance CPDOE will play an important rule in IOC to increase communication rate as well as decrease volume and weight.
The design of a phase-only diffractive WDM element, based on vector theory, is demonstrated. The adopted method of this design is a rigorous method based on the rigorous electromagnetic computation models the Beam propagation method (BPM)., Rayleigth-Sommerfield diffraction theory, and iterative optimization method. This phase-only diffractive optical WDM element (PDOE-WDM) is motivated by the intersatellite optical communication (IOC). And the motivation also raises the demands of large numerical aperture, polarization insensitivity and high diffraction efficiency. In order to predict the phase filter of DOE and the large angle diffraction precisely, a vigorous vector method has been adopted. The complex optical field right behind the BOE is computed by the Beam propagation method (BPM). And the diffraction between the back side of DOE and focusing plane is computed by the means of Rayleigth-Sommerfield (RS) diffraction theory, a more rigorous diffraction theory than Fresnel diffraction theory. The vector BPM method and the RS diffraction theory combined with FFT technology come along with the improvement of PDOE-WDM performances. And the high performance PDOE-WDM will play an important rule in IOC to increase communication rate as well as decrease volume and weight.
The theoretical and simulation angular dispersion characteristics of phase-only diffractive element are presented. The multi-wavelength dividing element is a key element in WDM system. Phase-only diffractive optical element (PDOE) used as WDM element has many merits, such as easy coupling, polarization insensitivity, low cross-talk and simple structure. There are two problems should be paid attention to in the design of PDOE. Firstly, the required large dispersion comes along with large diffraction angle. So the Fresnel assumption can not be satisfied in the diffraction calculation. Secondly, in the design of the PDOE, the multi-wavelength Yang-Gu phase retrieval algorithm is utilized to optimize the angular dispersion of PDOE. The convergence of YG algorithm is highly sensitive to the destination value. With the motivations above, it have been proceeded the study of the angular dispersion of PDOE. The theoretical and simulation results are presented in this paper. Based on the Phase Binary Equation, the angular dispersion is analyzed. Latter in this paper, an example PDOE has been designed. In the design process, the convergence of YG algorithm has been assured by the destination value carefully selected based the analysis results of angular dispersion. In the last part of this paper, the diffracted optical field behind the designed PDOE has been simulated with the method of Rayleigh-Sommerfeld diffraction theory. The simulation results are in quite accordance with the analytical results. So the angular dispersion of PDOE has been presented and validated by the works in this paper.