All-Optical Modulation and Ultrafast Switching in MWIR with Sub-Wavelength Structured Silicon

Abstract

We investigated and optimised the performance of the all-optical reflective modulation of the Mid-Wave Infrared (MWIR) signal by means of the optically-pumped sub-wavelength-structured optical membranes made of silicon. The membranes were optically pumped by a 60-femtosecond, 800-nm laser, while another laser operating in the MWIR ranging between 4 and 6 μ m was used to probe the optical response and modulation. We were able to achieve the conditions providing the modulation depth of 80% using the pump fluence of 3.8 mJ/cm 2 . To get a better insight into the performance and the modulation mechanism, we developed an optical model based on a combination of the Wentzel–Kramers–Brillouin approximation, Drude and Maxwell–Garnett theories. The model allowed us to estimate the values of the dielectric function, carrier concentration and scattering rate of the optically-excited membrane in the MWIR range. Using the model, we optimised the performance and found the conditions at which the reflective modulation can be operated with the ultrafast response of 0.55 ps and modulation contrast of 30%.

Localized Plasmon Field Effect of Gold Clusters Embedded in Nanoporous Silicon

“…The remnant of the beam was guided into an optical parametric amplifier (OPerA‐Solo) to generate a probe beam with the wavelength of 2.5 m and pulse duration of about 200 fs. [ 18,41 ] The optical path length of the pump beam was precisely adjusted by a computer‐controlled retroreflector, in order to adjust and scan the temporal overlap between pump and probe on the sample. The pump beam spot diameter on the sample was about 1 mm and the probe spot diameter was set to 600 m.…”

Ultrafast low-pump fluence all-optical modulation based on graphene-metal hybrid metasurfaces

“…All-optical modulation, compared to other techniques based on thermal, magnetic, acoustic, mechanical, and electrical effects, can achieve the highest modulation bandwidth up to THz. To date, all-optical modulation has been demonstrated based on a variety of materials and device designs, such as semiconductors waveguides 5 , colloidal plasmonic semiconductor nanocrystals 6 , chains of silicon nanoantennas 7 , gallium arsenide nanoparticles supporting Mie-type resonances 8 , nanostructured silicon membranes 9 , hot carrier effects of silver nanorods 10 , Tamm-plasmon resonance 11 , graphene-clad microfiber 12 , graphene–plasmonic slot waveguide 13 , thin-film absorber covered by graphene 14 , etc. Most of the modulators demonstrated experimentally are operated in the visible and near-infrared (IR) wavelength range.…”

“…Ultrafast optical modulation for mid-and far-IR wavelengths is highly desirable for ultrafast molecular spectroscopy 15 , space communication 16 – 18 , remote sensing 19 , biomedical diagnostics 20 – 23 , and astronomical applications 24 . Researchers have explored all-optical modulators based on optically pumped sub-wavelength-structured optical membranes made of silicon 9 , broadly tunable plasmons in solution-processed, degenerately doped oxide nanoparticles 25 , two-photon absorption in germanium-on-silicon waveguides 5 , and bulk Dirac fermions in MBE-grown crystalline cadmium arsenide (Cd3As2) 26 for wavelengths up to 6 µm. To date, it is still challenging to achieve ultrafast all-optical modulators for wavelengths >6 µm due to the inherent optical absorption and/or weak nonlinearity of optical materials.…”

High-speed and high-contrast two-channel all-optical modulator based on solution-processed CdSe/ZnS quantum dots

“…The AOMs have been widely inspected for their broad bandwidth, fast response and compact size, in which the light signal can be modulated in the photonic domain without exerting any external thermal, electronic, and other effects 5 , 8 , 9 . The progress of AOM goals not only at increasing the performance speed, but also at providing novel applications, such as broadband free-space communication, anti-fluctuation atmosphere imaging, and ultrafast time-of-flight detection, based on the current MIR detection technologies 16 , 17 .…”

“…So far, the range of telecommunication wavelengths has been the focus of most achievements and the researchers’ studies in the field of silicon optical modulators. The mid-infrared (MIR) to far-infrared (FIR) wavelength region has attracted less attention, in spite of its great potential and great solicitation on the market 16 , 21 . The most prominent applications in MIR, including free-space communication, security countermeasures, and thermal imaging employ the high transmission of the Earth’s atmosphere in the wavelength range between 3.5 μm and 5 μm.…”