Sampling technique for achieving full unit-circle coverage using a real-axis spatial light modulator

We investigate the possibility of using a real-axis spatial light modulator (SLM) to realize complexamplitude modulation with full coverage over the unit circle. The real-axis SLM produces a pixelated bipolar-amplitude wavefront. Each pixel is basically a spatial pulse width with the signal information being carried by the pulse’s amplitude. Data streams generated in this manner have real and imaginary components due to the relative even and odd symmetry of the pulse amplitude modulation. When the pulse rate is twice the minimum Nyquist rate for band-limited amplitude modulation, it is possible to resolve the signal into its quadrature phase components (real and imaginary terms). By changing the relative amplitude of these quadrature phase terms, any value within the complex plane is accessible. Since the SLM does not have any optical gain, coverage is limited to the unit circle in the complex plane.