Polarization-transforming reflector

We discuss in Section IX techniques for constructing a reflection mode spectrometer based on quasioptical techniques that will have a receiver input bandwidth A/ = 25 GHz. The quasioptical component that accomplishes this function is a Polarization Transforming Reflector (PTR) discussed in Howard et al. (1986) We use the PTR as a wave plate that rejects noise components outside of a narrow band. We discuss this point further in Section IX. Based on Eq. (78), this should allow a further reduction in Frt, min factor of 2 compared to the current spectrometer. We may... 

The layout for a novel scheme that overcomes the limitations of a Michelson duplexer is shown in Figure 7. The most important element of the spectrometer in Fig. 7 is the polarization-transforming reflector (PTR), which functions as a quarter-wave plate in this configuration. We will defer a detailed discussion of PTRs for the moment and focus instead on its functionality. To that end, consider Fig. 8a, where we have unfolded the optical layout between the PTR and the Fabry-Perot interferometer (FPI) in order to see the evolution of the electric field polarization more clearly. 

Let us now trace the polarization evolution of a Gaussian beam as it traverses the optical system shown in Fig. 7. Polarizer P passes radiation linearly polarized at 45° (L450) with respect to the normal to the plane of the page. The polarization-transforming reflector (PTR) converts linearly... 

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