Abstract
Infrared radiation reflection and transmission of a single layer of gold micropatch two-dimensional arrays, of patch length ∼m and width ∼m, have been carefully studied by a finite-difference time-domain (FDTD) method, and Fourier-transform infrared spectroscopy (FTIR). Through precision design of the micropatch array structure geometry, we achieve a significantly enhanced reflectance (85%), a substantial diffraction (10%), and a much reduced transmittance (5%) for an array of only 15% surface metal coverage. This results in an efficient far-field optical coupling with promising practical implications for efficient mid-infrared photodetectors. Most importantly we find that the propagating electromagnetic fields are transiently concentrated around the gold micropatch array in a time duration of tens of ns, providing us with a novel efficient near-field optical coupling.
Highlights
The interaction between light and microstructured materials offers great advantages for a wide range of applications including optoelectronics [1,2], bioimagings [3,4] as well as space exploitation, e.g., Laser Interferometer Gravitational-Wave Observatory (LIGO) where radiations of 30 Hz∼7.0 kHz are used to study cosmic gravitational waves [5]
We further studied a perfect Au sheet in which we observed a direct reflection of approximately 92%, very small transmission, virtually no diffraction at all, and a significant loss, see Figure 4, for the Infrared radiation (IR) radiation of wavelengths of our interest
The temporal/transient fields shown in Figure 3, that caused the strong diffraction, approximately 10% in Figure 2a, can be absorbed by placing the IR receiver close to the Au micropatch array plane, i.e., the near-field optical coupling
Summary
The interaction between light and microstructured materials offers great advantages for a wide range of applications including optoelectronics [1,2], bioimagings [3,4] as well as space exploitation, e.g., Laser Interferometer Gravitational-Wave Observatory (LIGO) where radiations of 30 Hz∼7.0 kHz are used to study cosmic gravitational waves [5]. Subwavelength hole array perforated in metal thin film was shown to significantly enhance light absorption [8,10,11], whilst three-dimensional microstructure gratings [12] and synchronously wired infrared antennas [13] have been designed and fabricated to demonstrate improved IR absorption. Enhanced light absorption, mostly in the visible and near infrared (NIR) spectral ranges, through hole array perforated in metal thin film was initially observed and reported in 1998 [24]. We combine computational simulations with experimental characterizations of nanofabricated single layers of two-dimensional gold micropatch arrays to understand and design wavelength-selective far- and near-field infrared optical couplings that operate in mid-IR wavelength regime aiming for, e.g., CO2 and alcohol sensing [30]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
