We report on the observation of the helicity-dependent photoresponse of the 20-μm-thick silver–palladium (Ag/Pd) nanocomposite films. In the experiment, 120 fs pulses of Ti:S laser induced in the film an electric current perpendicular to the incidence plane. The photoinduced current is a linear function of the incident beam power, and its sign depends on the beam polarization and angle of incidence. In particular, the current is zero for the p- and s-polarized beams, while its sign is opposite for the right- and left-circularly polarized beams. By comparing experimental results with theoretical analysis, we show that the photoresponse of the Ag/Pd nanocomposite originates from the photon drag effect.

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We performed the investigation of the polarization-sensitive photocurrent generated in silver-palladium metal-semiconductor nanocomposite films under irradiation with nanosecond laser pulses at the wavelength of 2600 nm. It is shown that in both the transverse and the longitudinal configuration, the surface photogalvanic (SPGE) and photon drag effects (PDE) contribute to the observed photocurrent. However, the temporal profile of the transverse photocurrent pulse is monopolar at any polarization and angle of incidence, while the temporal profile of the longitudinal photocurrent pulse depends on the polarization of the excitation beam. Specifically, the irradiation of the film with the s-polarized excitation beam produces a monopolar photoresponse, while at p-polarized excitation, the photoresponse is bipolar, having a short front and long tail. Obtained experimental results are in agreement with the developed phenomenological theory, which describes transverse and longitudinal photocurrents due to SPGE and PDE in terms of relevant second-order nonlinear susceptibilities and allows us to obtain their dependences on the angle of incidence and polarization of the excitation laser beam. The pronounced dependence of the photocurrent on the angle of incidence and polarization of the excitation beam opens avenues toward the development of polarization- and position-sensitive detectors for industrial and space applications.

Plasmonic metasurfaces exhibiting collective responses known as surface lattice resonances (SLRs) show potential for realizing flat photonic components for wavelength-selective processes, including lasing and optical nonlinearities. However, postfabrication tuning of SLRs remains challenging, limiting the applicability of SLR-based components. Here, we demonstrate how the properties of high quality factor SLRs are easily modified by breaking the symmetry of the nanoparticle surroundings. We break the symmetry by changing the refractive index of the overlying immersion oil by controlling the ambient temperature of the device. We show that a modest temperature change of 10 °C can increase the quality factor of the SLR from 400 to 750. Our results demonstrate accurate and reversible modification of the properties of the investigated SLRs, paving the way toward tunable SLR-based photonic devices. More generally, we show how symmetry breaking of the environment can be utilized for efficient and potentially ultrafast modification of the SLR properties.