We present a terahertz-SLM with a frequency working range from 1.0 THz to 2.3 THz. Over the complete frequency range, the spatial modulation contrast exceeds 50% with a peak modulation contrast of 87% at 1.38 THz. The pixels of the SLM consist of mirror arrays that can be selectively actuated by a bias voltage of 35 V. Each individual pixel can either work as a grating, that diffracts terahertz radiation away from the detector, or as a flat mirror, that reflects all terahertz radiation into the detector. The mirrors have a size of 220 μm x 100 μm. Due to the wide frequency working bandwidth of more than 1 THz, such modulators can be used as spatial light modulators in terahertz coded aperture imaging spectroscopes with single-pixel detectors.
Recent studies in spintronics have highlighted ultrathin magnetic metallic multilayers as a novel and very promising class of broadband terahertz radiation sources. Such spintronic multilayers consist of ferromagnetic (FM) and non-magnetic (NM) thin films. When triggered by ultrafast laser pulses, they generate pulsed THz radiation due to the inverse spin-Hall effect – a mechanism that converts optically driven spin currents from the magnetized FM layer into transient transverse charge currents in the NM layer, resulting in THz emission. As THz emitters, FM/NM multilayers have been intensively investigated so far only at 800-nm excitation wavelength using femtosecond Ti:sapphire lasers. In this work, we demonstrate that an optimized spintronic bilayer structure of 2-nm Fe and 3-nm Pt grown on 500 μm MgO substrate is just as effective as a THz radiation source when excited either at λ = 400 nm, λ = 800 nm or at λ = 1550 nm by ultrafast laser pulses (pulse width ~100 fs, repetition rate ~100 MHz). Even at low incident power levels, the Fe/Pt spintronic emitter exhibits efficient generation of THz radiation at all three excitation wavelengths. The efficient THz emitter operation at 1550 nm facilitates the integration of such spintronic emitters in THz systems driven by relatively low cost and compact fs fiber lasers without the need for frequency conversion.