  Identifying materials with an efficient spin-to-charge conversion is crucial
for future spintronic applications. The spin Hall effect is a central mechanism
as it allows for the interconversion of spin and charge currents. Spintronic
material research aims at maximizing its efficiency, quantified by the spin
Hall angle $\Theta_{\textrm{SH}}$ and the spin-current relaxation length
$\lambda_{\textrm{rel}}$. We develop an all-optical method with large sample
throughput that allows us to extract $\Theta_{\textrm{SH}}$ and
$\lambda_{\textrm{rel}}$. Employing terahertz spectroscopy, we characterize
magnetic metallic heterostructures involving Pt, W and Cu$_{80}$Ir$_{20}$ in
terms of their optical and spintronic properties. We furthermore find
indications that the interface plays a minor role for the spin-current
transmission. Our analytical model is validated by the good agreement with
literature DC values. These findings establish terahertz emission spectroscopy
as a reliable tool complementing the spintronics workbench.
