The emission of a Nd-YAG laser (EKSPLA SL234) at 1064~nm with pulse duration of 100~ps is used to provide sub-ns time resolution. Two polarizers and a half-wave plate for 1064~nm are used to tune laser pulse energy. The second half-wave plate is installed in order to rotate the polarization of the laser beam relative to the electrodes. A red colored glass filter is used to suppress light at the second harmonic generated in the optical elements due to high laser intensity. the beam is directed along the electrodes. After the light is focused to the middle of the discharge gap along the electrodes in the plane located at half of the electrode thickness. The beam is collimated and the second harmonic is separated from the fundamental one by a dichroic mirror. A blue colored glass filter eliminates the residual light at 1064~nm, and, finally, a laser line filter with center wavelength at 532~nm and FWHM of 1~nm (Thorlabs FL532-1) is installed at the entrance of a photomultiplier tube (PMT; Hamamatsu H11901-210). Fast photodiode (Thorlabs FDS015) with rise time of about 200~ps is used to record timestamp of the laser pulse relative to the discharge. The time of light propagation from the diode to the discharge cell and the delay of the signal propagation in the BNC cable are taken into account to determine the time shift between E-FISH signal and signal from high voltage and current probes. Then a precise synchronization is performed by measurement of a Laplacian field at conditions without ignition of the discharge. The energy of the laser pulse is monitored by another photodiode (Thorlabs DET10A), which has a bigger area and, thus, is less sensitive to pulse-to-pulse laser profile variation. A glass diffuser plate is installed in front of the diode to additionally reduce the influence of possible laser profile instabilities.