We present a new coherent optical Beamformer for the receive mode based on a Dual Frequency Laser and Spatial Light Modulation matrixes. This coherent architecture, described and detailed by different building blocks, allows a full reconfiguration of the beam thanks to the SLM matrixes and a first down conversion due to the conjoint use of a heterodyne source and an external modulator.
We show that diode-pumped solid-state lasers can generate tunable high-purity microwave signals. In the case of a single-axis cavity containing an adjustable linear phase anisotropy, orthogonal linear eigenstates oscillate with a continuously tunable frequency difference. The maximum beat frequency is fixed by the laser cavity length and can reach a few tens of GHz. In order to reach the THz range, insertion of a double refraction crystal inside the laser cavity creates a two-axis laser that allows one to choose independently the frequencies of the two eigenstates. In this case the maximum beat frequency is fixed by the active medium gain bandwidth which is of a few THz for an Er:Yb:glass active medium. We show that doubling the two frequencies emitted by such a two-axis laser at 1.55 mum yields a source of tunable cw THz beat notes suitable for photomixing in GaAs-based THz emitters. Moreover, the beat notes generated by diode-pumped solid-state lasers can be phase-locked to microwave local oscillators. In particular, we show that a single-axis Er:Yb:glass laser provides a beat note continuously tunable from 0 to 20 GHz with a 170 muHz line width. The phase noise of such a source is measured to be lower than -130 dBc/Hz at 100 kHz offset from the carrier.