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Dive into the research topics where Sulochana Dhar is active.

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Featured researches published by Sulochana Dhar.


Journal of Biophotonics | 2009

Chip scale integrated microresonator sensing systems.

Nan Marie Jokerst; Matthew Royal; Sabarni Palit; Lin Luan; Sulochana Dhar; Talmage Tyler

Medicine, environmental monitoring, and security are application areas for miniaturized, portable sensing systems. The emerging integration of sensors with other components (electronic, photonic, fluidic) is moving sensing toward higher levels of portability through the realization of self-contained chip scale sensing systems. Planar optical sensors, and in particular, microresonator sensors, are attractive components for chip scale integrated sensing systems because they are small, have high sensitivity, can be surface customized, and can be integrated singly or in arrays in a planar format with other components using conventional semiconductor fabrication technologies. This paper will focus on the progress and prospects for the integration of microresonator sensors at the chip scale with photonic input/output components and with sample preparation microfluidics, toward self-contained, portable sensing systems.


Optics Express | 2012

Planar, flattened Luneburg lens at infrared wavelengths

John Hunt; Talmage Tyler; Sulochana Dhar; Yu-Ju Tsai; Patrick Bowen; Stéphane Larouche; Nan Marie Jokerst; David R. Smith

Employing artificially structured metamaterials provides a means of circumventing the limits of conventional optical materials. Here, we use transformation optics (TO) combined with nanolithography to produce a planar Luneburg lens with a flat focal surface that operates at telecommunication wavelengths. Whereas previous infrared TO devices have been transformations of free-space, here we implement a transformation of an existing optical element to create a new device with the same optical characteristics but a user-defined geometry.


IEEE Transactions on Biomedical Circuits and Systems | 2009

Progress in Chip-Scale Photonic Sensing

Nan Marie Jokerst; Lin Luan; Sabarni Palit; Matthew Royal; Sulochana Dhar; Martin A. Brooke; Talmage Tyler

Chip-scale integrated planar photonic sensing systems for portable diagnostics and monitoring are emerging, as photonic components are integrated into systems with silicon (Si), Si complementary metal-oxide semiconductor, and fluidics. This paper reviews progress in these areas. Medical and environmental applications, candidate photonic sensors, integration methodologies, integrated subsystem demonstrations, and challenges facing this emerging field are discussed in this paper.


Physical Review B | 2012

Electronically reconfigurable metal-on-silicon metamaterial

Yaroslav A. Urzhumov; Jae Seung Lee; Talmage Tyler; Sulochana Dhar; Vinh N. Nguyen; Nan Marie Jokerst; Paul Schmalenberg; David R. Smith

This work was supported by Toyota Motor Engineering and Manufacturing North America and partially supported by the Air Force Office of Scientific Research (Grant No. FA9550-09-1-0562).


Optics Express | 2014

High responsivity, low dark current, heterogeneously integrated thin film Si photodetectors on rigid and flexible substrates

Sulochana Dhar; David Marshall Miller; Nan Marie Jokerst

We report thin film single crystal silicon photodetectors (PDs), composed of 13- 25 μm thick silicon, heterogeneously bonded to transparent Pyrex® and flexible Kapton® substrates. The measured responsivity and dark current density of the PDs on pyrex is 0.19 A/W - 0.34 A/W (λ = 470 nm - 600 nm) and 0.63 nA/cm(2), respectively, at ~0V bias. The measured responsivity and dark current density of the flexible PDs is 0.16 A/W - 0.26 A/W (λ = 470 nm - 600 nm) and 0.42 nA/cm(2), respectively, at a ~0V bias. The resulting responsivity-to-dark current density ratios for the reported rigid and flexible PDs are 0.3-0.54 cm(2)/nW and 0.38-0.62 cm(2)/nW, respectively. These are the highest reported responsivity-to-dark current density ratios for heterogeneously bonded thin film single crystal Si PDs, to the best of our knowledge. These PDs are customized for applications in biomedical imaging and integrated biochemical sensing.


Biomedical Optics Express | 2012

A diffuse reflectance spectral imaging system for tumor margin assessment using custom annular photodiode arrays.

Sulochana Dhar; Justin Y. Lo; Gregory M. Palmer; Martin A. Brooke; Brandon S. Nichols; Bing Yu; Nirmala Ramanujam; Nan Marie Jokerst

Diffuse reflectance spectroscopy (DRS) is a well-established method to quantitatively distinguish between benign and cancerous tissue for tumor margin assessment. Current multipixel DRS margin assessment tools are bulky fiber-based probes that have limited scalability. Reported herein is a new approach to multipixel DRS probe design, which utilizes direct detection of the DRS signal by using optimized custom photodetectors in direct contact with the tissue. This first fiberless DRS imaging system for tumor margin assessment consists of a 4 × 4 array of annular silicon photodetectors and a constrained free-space light delivery tube optimized to deliver light across a 256 mm2 imaging area. This system has 4.5 mm spatial resolution. The signal-to-noise ratio measured for normal and malignant breast tissue-mimicking phantoms was 35 dB to 45 dB for λ = 470 nm to 600 nm.


PLOS ONE | 2013

Wavelength Optimization for Quantitative Spectral Imaging of Breast Tumor Margins

Justin Y. Lo; J. Quincy Brown; Sulochana Dhar; Bing Yu; Gregory M. Palmer; Nan Marie Jokerst; Nirmala Ramanujam

A wavelength selection method that combines an inverse Monte Carlo model of reflectance and a genetic algorithm for global optimization was developed for the application of spectral imaging of breast tumor margins. The selection of wavelengths impacts system design in cost, size, and accuracy of tissue quantitation. The minimum number of wavelengths required for the accurate quantitation of tissue optical properties is 8, with diminishing gains for additional wavelengths. The resulting wavelength choices for the specific probe geometry used for the breast tumor margin spectral imaging application were tested in an independent pathology-confirmed ex vivo breast tissue data set and in tissue-mimicking phantoms. In breast tissue, the optical endpoints (hemoglobin, β-carotene, and scattering) that provide the contrast between normal and malignant tissue specimens are extracted with the optimized 8-wavelength set with <9% error compared to the full spectrum (450–600 nm). A multi-absorber liquid phantom study was also performed to show the improved extraction accuracy with optimization and without optimization. This technique for selecting wavelengths can be used for designing spectral imaging systems for other clinical applications.


IEEE Photonics Technology Letters | 2010

Planar Integrated Optical Detection of a Hybrid Long-Range Surface Plasmon Using an InGaAs Inverted-MSM Detector Bonded to Silicon

Sulochana Dhar; Aloyse Degiron; David R. Smith; Nan Marie Jokerst

An InxGa1-xAs thin-film inverted metal-semiconductor-metal photodetector has been integrated with a gold hybrid long-range surface plasmon waveguide on silicon. This integrated structure enables planar integrated optical detection of a long-range surface plasmon wave at a wavelength of 1.55 μm.


Proceedings of SPIE | 2012

Diffuse Reflectance Spectral Imaging for Breast Tumor Margin Assessment

Justin Y. Lo; Sulochana Dhar; Bing Yu; Martin A. Brooke; T. F. Kuech; Nan Marie Jokerst; Nimmi Ramanujam

Diffuse reflectance spectroscopy has been previously explored as a promising method for providing real-time visual maps of tissue composition to help surgeons determine breast lumpectomy margins and to ensure the complete removal of a tumor during surgery. We present the simple design, validation, and implementation of a compact and cost-effective spectral imaging system for the application of tumor margin assessment. Our new system consists of a broadband source with bandpass filters for illumination and a fabricated custom 16-pixel photodiode imaging array for the detection of diffuse reflectance. The system prototype was characterized in tissue-mimicking phantoms and has an SNR of greater than 40 dB in phantoms, animals, and human tissue. We show proof-of-concept for performing fast, wide-field spectral imaging with a simple, inexpensive design. The strategy also allows for the scaling to higher pixel number and density in future iterations of the system.


ieee photonics conference | 2011

A custom wide-field spectral imager for breast cancer margin assessment

Sulochana Dhar; Justin Y. Lo; Bing Yu; Talmage Tyler; Martin A. Brooke; Nimmi Ramanujam; Nan Marie Jokerst; T. F. Kuech

A custom imaging array optimized for wide-field diffuse reflectance spectroscopy imaging for breast cancer margin diagnosis has been designed and implemented, with improvements over a previously reported system.

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