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%.
Highlights
Silicon, as the most common semiconductor in electronic integrated circuits, has been considered as one of the best candidates for the natural hybrid of photonic and electronic devices [1]
Thermal-optical modulation was investigated by Cocorullo et al, but it is only suitable for low repetition rate applications due to its slow response [9,10]
The low-intensity part was used as the pump beam, while the high-intensity part was directed into an Optical Parametric Amplifier (OPA) to generate the signal beam with a tunable wavelength in the range between 4 and 6 μm
Summary
As the most common semiconductor in electronic integrated circuits, has been considered as one of the best candidates for the natural hybrid of photonic and electronic devices [1]. Thermal-optical modulation was investigated by Cocorullo et al, but it is only suitable for low repetition rate applications due to its slow response [9,10]. The free carrier plasma dispersion effect, where the material optical response varied with the free carrier density, is the most commonly-investigated modulation mechanism in silicon [11]. The free carrier density can be altered by the carrier depletion, accumulation or injection by either electronic or optical means [12]. The latter case is known as all-optical modulation, Appl.
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