  We measured reflectivity on static stripe-ordered
La$_{1.84-y}$Nd$_y$Sr$_{0.16}$CuO$_4$ (LNSCO) $y$\,=\,0.1, 0.2, 0.3, and 0.4 by
means of reflective terahertz time-domain spectroscopy (THz-TDS) with electric
field polarized along c-axis, in which one can obtain lower frequency
information than the conventional Fourier transform type spectrometer.
Recently, two-dimensional superconducting (2DSC) property
\cite{tajima,schafgans,li}, intra-layer perfect conductivity not accompanied
with inter-layer superconducting behavior, was reported on LNSCO
($x$\,=0.15\,,\,$y$\,$\geq$\,0.2). We observed the existence of Josephson
plasma edge, which suggests that 2DSC is not realized in these compounds.
