In this work, lightly-doped black silicon (BSi) is fabricated using cryogenic DRIE in a maskless manner and its transmittance and reflectance are measured using an integrating sphere and a spectrometer in the near infrared (NIR) wavelength range of 1300 nm - 2500 nm. Then, the surface is cleaned and copper (Cu) is deposited on the BSi using the wet deposition technique of electroless plating, enabling high throughput coating. The copper ions are deposited on the BSi surface in a Cu sulphate solution, taking advantage of the conformity of the plating to the nano/micro structures of the BSi targeting lower reflectance and higher absorptivity. The Cu-plated BSi is measured and observed to have a minimum reflectance of 10% compared to 30% in the case of BSi, and a minimum transmittance of 10% compared to 40% in the bare black silicon. Thus, the Cu-plated BSi has a maximum absorptivity of about 80% compared to 30% in the bare BSi. The absorptivity is found to decrease with increasing the wavelength. This enhancement using the electroless Cu plating further qualifies the BSi as a candidate for NIR thermal light sources.
All manufactured sampled grating structures are mainly used for `wavelength tunability'. In this paper we succeeded in generating two modes by using Sampled Grating DFB laser. The two modes, will be optically heterodyned on a photodetector for mm-wave (via mode beating) signal generation. The advantage of that design is its size compactness (a single section, single electrode fed with a DC current supply), stable mode spacing, and relatively lower cost compared with other means of mm-wave generation. The simulation results will be presented using the well established model. Two parameters are shown to be affecting on the dual mode spacing and amplitude: the coupling coefficient and the carrier density variation along the (SG) structure. The former (coupling coefficient) mainly influences the mode spacing which is translated into the mm-wave frequency at the photodetector level. The anomalous coupling coefficient behavior leading to a quasi-stable mode spacing independent on the DFB section length increase is studied, interpreted and optimized. The latter (carrier density) plays a dramatic effect on that structure, resulting on fading away one of the two modes. We, succeeded in confining these two chirped modes into the structure by detuning the gratings. Finally, detuned grating effect will be explained.
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