Shahriar Farhadi - Academia.edu (original) (raw)
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Massachusetts Institute of Technology (MIT)
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Papers by Shahriar Farhadi
Scientific Reports, 2021
Detection of low-index materials such as aerogels and also detection of refractive index variatio... more Detection of low-index materials such as aerogels and also detection of refractive index variations in these materials is still a challenging task. Here, a high figure of merit (FOM) sensor based on plasmon-induced transparency (PIT) is proposed for the detection of aerogel refractive index changes. In the proposed PIT sensor, the transparency window in an opaque region arises from the coupling between surface plasmon polariton (SPP) mode and planar waveguide mode. By comprising sub-wavelength grating (SWG) in the planar waveguide region, the maximum of the electric field of waveguide occurs in a low index media. This facilitates detection of the aerogels when they are used as the low index material (sensing material). Application of the subwavelength grating waveguide also improves the sensitivity of the sensor by a factor of six compared to a conventional structure with a homogenous waveguide. The proposed structure has a quality factor of Q ≥ 1800, and a reflection of 86%, and ca...
Applied Physics B, 2020
A compact and ultra-wideband multimode interferometer (MMI)-based polarization beam splitter (PBS... more A compact and ultra-wideband multimode interferometer (MMI)-based polarization beam splitter (PBS) is designed in a silicon-on-insulator (SOI) platform. A sub-wavelength grating (SWG) structure is employed in the multimode region to reduce the overall length of the structure and also increase its operating bandwidth. Instead of using the beat-length difference to separate the transverse electric (TE) and transverse magnetic (TM) polarized waves, the TM waves are directly coupled to the output bar port through an interconnecting waveguide, while the TE polarized waves are transmitted to the cross port by the self-imaging process. This substantially reduces the length of the PBS and the overall footprint can be as small as 4.8 × 21 µm 2. The proposed device exhibits the extinction ratio of more than 15 dB in a 250 nm wavelength range (1.38-1.63 µm) and more than 12 dB in the 350 nm wavelength range (1.3-1.65 µm) for the TE and TM polarizations, respectively. In addition, the insertion loss remains below 1.2 dB for both the TE and TM polarization in a broad wavelength range from 1.38 to 1.54 µm. The proposed PBS can be fabricated by a single-step etching process on an SOI wafer. Moreover, our simulations show the robustness of the PBS performance to the fabrication errors'.
Scientific Reports, 2021
Detection of low-index materials such as aerogels and also detection of refractive index variatio... more Detection of low-index materials such as aerogels and also detection of refractive index variations in these materials is still a challenging task. Here, a high figure of merit (FOM) sensor based on plasmon-induced transparency (PIT) is proposed for the detection of aerogel refractive index changes. In the proposed PIT sensor, the transparency window in an opaque region arises from the coupling between surface plasmon polariton (SPP) mode and planar waveguide mode. By comprising sub-wavelength grating (SWG) in the planar waveguide region, the maximum of the electric field of waveguide occurs in a low index media. This facilitates detection of the aerogels when they are used as the low index material (sensing material). Application of the subwavelength grating waveguide also improves the sensitivity of the sensor by a factor of six compared to a conventional structure with a homogenous waveguide. The proposed structure has a quality factor of Q ≥ 1800, and a reflection of 86%, and ca...
Applied Physics B, 2020
A compact and ultra-wideband multimode interferometer (MMI)-based polarization beam splitter (PBS... more A compact and ultra-wideband multimode interferometer (MMI)-based polarization beam splitter (PBS) is designed in a silicon-on-insulator (SOI) platform. A sub-wavelength grating (SWG) structure is employed in the multimode region to reduce the overall length of the structure and also increase its operating bandwidth. Instead of using the beat-length difference to separate the transverse electric (TE) and transverse magnetic (TM) polarized waves, the TM waves are directly coupled to the output bar port through an interconnecting waveguide, while the TE polarized waves are transmitted to the cross port by the self-imaging process. This substantially reduces the length of the PBS and the overall footprint can be as small as 4.8 × 21 µm 2. The proposed device exhibits the extinction ratio of more than 15 dB in a 250 nm wavelength range (1.38-1.63 µm) and more than 12 dB in the 350 nm wavelength range (1.3-1.65 µm) for the TE and TM polarizations, respectively. In addition, the insertion loss remains below 1.2 dB for both the TE and TM polarization in a broad wavelength range from 1.38 to 1.54 µm. The proposed PBS can be fabricated by a single-step etching process on an SOI wafer. Moreover, our simulations show the robustness of the PBS performance to the fabrication errors'.