Photonics and Quantum Detection

Here, we report the temporal diffraction of electromagnetic waves in the optical telecommunication range for real epsilon-near-zero indium-tin-oxide (ITO) thin films sandwiched between fused silica and gold layers (FS/ITO/Au), fabricated using high-frequency alternating current sputtering under different substrate heat treatments (RT, 250 °C, 300 °C). Thermally treated ITO thin films show increase in dielectric constants, a shift of ENZ values towards lower wavelengths, higher number of free carriers, and enhanced carrier mobility. Pump and probe laser pulses with similar central frequencies, ranging from 134.9 THz to 221.6 THz (2.2 μm to 1.35 μm), corresponding to the real part of dielectric permittivity, ε1 = 0 to 1, were used to observe the temporal diffraction patterns at 70°. Pump laser double-pulses of 100 fs, 225 fs, and 300 fs, along with probe laser pulses of 200 fs, 400 fs, 794 fs, and 900 fs, were employed to optimize the diffraction, which occurs when the pump double-pulses completely overlap in time and size with the probe pulse. A correlation was identified between temporal slit separation and period of oscillation in the diffraction pattern of FS/ITO250/Au and FS/ITO300/Au. Specifically, pump double-pulses with time slits of 425 fs and 850 fs, both overlapping with the probe pulses of 794 fs and 900 fs, show a reciprocal relation between the temporal slit separation and the oscillation period in the diffraction pattern.