Combined Diffuse Optical Tomography (DOT) and MRI System for Cancer Imaging in Small Animals

Recently, there has been a great amount of interest in developing multi-modality imaging techniques for oncologic research and clinical studies with the aim of obtaining complementary information and, thus, improving the detection and characterization of tumors. In this present work, the details of a combined MR-diffuse optical imaging system for dual-modality imaging of small animals are given. As a part of this effort, a multi-spectral frequency domain diffuse optical tomography system is integrated with an MRI system. Here, a network analyzer provides the rf modulation signal for the laser diodes and measures the amplitude and the phase of the detected signals. Photomultiplier tubes are utilized to measure low-level signals. The integration of this optical imaging system with the 4T MRI system is realized by incorporating a fiber adaptive interface inside the MR magnet. Coregistration is achieved by a special probe design utilizing fiducial markers. A finite element algorithm is used to solve the diffusion equation and an inverse solver based on this forward solver is implemented to calculate the absorption and scattering maps from the acquired data. The MR a priori information is used to guide the optical reconstruction algorithm. Phantom studies show that the absorption coefficient of a 7 mm inclusion in an irregular object located in 64 mm phantom is recovered with 11 % error when MR a priori information is used. ENU induced tumor model is used to test the performance of the system in vivo

Combined diffuse optical tomography (DOT) and MRI system for cancer imaging in small animals

Recently, there has been a great amount of interest in developing multi-modality imaging techniques for oncologic research and clinical studies with the aim of obtaining complementary information and, thus, improving the detection and characterization of tumors. In this present work, the details of a combined MR-diffuse optical imaging system for dual-modality imaging of small animals are given. As a part of this effort, a multi-spectral frequency domain diffuse optical tomography system is integrated with an MRI system. Here, a network analyzer provides the rf modulation signal for the laser diodes and measures the amplitude and the phase of the detected signals. Photomultiplier tubes are utilized to measure low-level signals. The integration of this optical imaging system with the 4T MRI system is realized by incorporating a fiber adaptive interface inside the MR magnet. Coregistration is achieved by a special probe design utilizing fiducial markers. A finite element algorithm is used to solve the diffusion equation and an inverse solver based on this forward solver is implemented to calculate the absorption and scattering maps from the acquired data. The MR a priori information is used to guide the optical reconstruction algorithm. Phantom studies show that the absorption coefficient of a 7 mm inclusion in an irregular object located in 64 mm phantom is recovered with 11 % error when MR a priori information is used. ENU induced tumor model is used to test the performance of the system in vivo

The superlinear carrier absorption enhanced silicon MOS micro-ring modulator

We demonstrate superlinear plasma absorption effects in silicon MOS micro-ring modulators, which have been harnessed to enhance the optical modulation depth. Operating speed up to 100 Gbaud with a of BER &lt;1e-6 is achieved. </p

Strong Electro-Absorption in GeSi Epitaxy on Silicon-on-Insulator (SOI)

We have investigated the selective epitaxial growth of GeSi bulk material on silicon-on-insulator substrates by reduced pressure chemical vapor deposition. We employed AFM, SIMS, and Hall measurements, to characterize the GeSi heteroepitaxy quality. Optimal growth conditions have been identified to achieve low defect density, low RMS roughness with high selectivity and precise control of silicon content. Fabricated vertical p-i-n diodes exhibit very low dark current density of 5 mA/cm2 at −1 V bias. Under a 7.5 V/µm E-field, GeSi alloys with 0.6% Si content demonstrate very strong electro-absorption with an estimated effective ∆α/α around 3.5 at 1,590 nm. We compared measured ∆α/α performance to that of bulk Ge. Optical modulation up to 40 GHz is observed in waveguide devices while small signal analysis indicates bandwidth is limited by device parasitics

Strong Electro-Absorption in GeSi Epitaxy on Silicon-on-Insulator (SOI)

We have investigated the selective epitaxial growth of GeSi bulk material on silicon-on-insulator substrates by reduced pressure chemical vapor deposition. We employed AFM, SIMS, and Hall measurements, to characterize the GeSi heteroepitaxy quality. Optimal growth conditions have been identified to achieve low defect density, low RMS roughness with high selectivity and precise control of silicon content. Fabricated vertical &lt;em&gt;p&lt;/em&gt;-&lt;em&gt;i&lt;/em&gt;-&lt;em&gt;n&lt;/em&gt; diodes exhibit very low dark current density of 5 mA/cm&lt;sup&gt;2&lt;/sup&gt; at −1 V bias. Under a 7.5 V/µm E-field, GeSi alloys with 0.6% Si content demonstrate very strong electro-absorption with an estimated effective ∆α/α around 3.5 at 1,590 nm. We compared measured ∆α/α performance to that of bulk Ge. Optical modulation up to 40 GHz is observed in waveguide devices while small signal analysis indicates bandwidth is limited by device parasitics

Dataset in support of the journal article &#39;Harnessing plasma absorption in silicon MOS ring modulators&#39;

Please read the readme.docx file for more detailed information of the publication.</span

Harnessing plasma absorption in silicon MOS ring modulators

High bandwidth, low power and compact silicon electro-optical modulators are essential for future energy efficient and densely integrated optical data communication circuits. The all-silicon plasma dispersion effect ring resonator modulator is an attractive prospect. However, its performance is currently limited by the trade-off between modulation depth and switching speed dictated by its quality factor. Here we introduce a mechanism to leap beyond this limitation by harnessing the plasma absorption induced in a silicon MOS waveguide to enhance the extinction ratio of a low quality factor, high-speed ring modulator. Fabricated devices have demonstrated a modulation depth ~ 27dB for a bias ~ 3.5V. Modulation enhancement has been observed for frequencies of operation from kHz to GHz with data modulation up to 100Gbit/s on-off keying demonstrated, paving the evolution of optical interconnects to 100 Gbaud and beyond per wavelength