The high temperature superconductors which were discovered in 1986 still continue to pose major challenges to scientists. Not only is the mechanism for superconductivity not known, but the nature of the superconducting state and the motion of vortices continue to be debated intensely. We study the microwave response of superconductors, both for understanding the nature of superconductivity, the dynamics of vortices and for practical applications in microwave devices.
The principal areas of our research are:
- Fundamental measurements and analysis of the penetration depth and surface impedance of superconductors, with a view to understanding the pairing state, the quasiparticle spectrum and the gap parameter
- Vortex dynamics at high (rf and microwave) frequencies to obtain quantiative measurements of parameters such as pinning force constants, vortex viscosity, critical fields, melting and vortex glass transitions
- Flux penetration and critical state dynamics
- Josephson type nonlinear phenomena at microwave frequencies
- Development of novel measurement techniques, such as the “hot finger” cavity method to measure surface impedance, tunnel diode technique of measuring penetration depth, patterned film structures to study vortex dynamics, modulated microwave absorption
The materials we study are the cuprate High Tc superconductors, borocarbides, and organic superconductors.
Our work in Superconductivity is supported by:
- National Science Foundation
- Division of Materials Research and Division of Electrical and Communications Systems, Rome Laboratory, Hanscom AFB (an AFOSR lab)
Related Publications
Faegh, Samira; Jalili, Nader; Sridhar, Srinivas Sensor system utilizing piezoelectric microcantilever coupled with resonating circuit Miscellaneous 2018, (US Patent 9,921,226). Ozturk, Birol; Yavuzcetin, Ozgur; Sridhar, Srinivas A novel coupled resonator photonic crystal design in lithium niobate for electrooptic applications Journal Article In: International Journal of Optics, vol. 2015, 2015. Abstract | Tags: Nanomedicine, Sensors Faegh, Samira; Jalili, Nader; Sridhar, Srinivas Ultrasensitive piezoelectric-based microcantilever biosensor: Theory and experiment Journal Article In: IEEE/ASME Transactions on Mechatronics, vol. 20, no. 1, pp. 308–312, 2014. Yavuzcetin, O; Perry, Nicholas R; Malley, Sean T; Dally, Rebecca L; Novikov, Herman P; Ozturk, Birol; Sridhar, Srinivas Fabrication and characterization of single mode annealed proton exchanged waveguides in-x-cut lithium niobate Journal Article In: Optical Materials, vol. 36, no. 2, pp. 372–375, 2013. Faegh, Samira; Jalili, Nader; Yavuzcetin, Ozgur; Nagesha, Dattatri; Kumar, Rajiv; Sridhar, Srinivas A cost-effective self-sensing biosensor for detection of biological species at ultralow concentrations Journal Article In: Journal of Applied Physics, vol. 113, no. 22, pp. 224905, 2013. Faegh, Samira; Jalili, Nader; Sridhar, Srinivas A self-sensing piezoelectric microcantilever biosensor for detection of ultrasmall adsorbed masses: theory and experiments Journal Article In: Sensors, vol. 13, no. 5, pp. 6089–6108, 2013. Yavuzcetin, Ozgur; Novikov, Herman P; Dally, Rebecca L; Malley, Sean T; Perry, Nicholas R; Ozturk, Birol; Sridhar, Srinivas Photonic crystal fabrication in lithium niobate via pattern transfer through wet and dry etched chromium mask Journal Article In: Journal of Applied Physics, vol. 112, no. 7, pp. 074303, 2012. Sridhar, Srinivas; Gultepe, Evin; Nagesha, Dattatri Large scale nanoelement assembly method for making nanoscale circuit interconnects and diodes Miscellaneous 2011, (US Patent App. 12/936,938). Yavuzcetin, Ozgur; Ozturk, Birol; Xiao, Dong; Sridhar, Srinivas Conicity and depth effects on the optical transmission of lithium niobate photonic crystals patterned by focused ion beam Journal Article In: Optical Materials Express, vol. 1, no. 7, pp. 1262–1271, 2011. Selvarasah, S; Chao, SH; Chen, C-L; Sridhar, S; Busnaina, A; Khademhosseini, A; Dokmeci, MR A reusable high aspect ratio parylene-C shadow mask technology for diverse micropatterning applications Journal Article In: Sensors and Actuators A: Physical, vol. 145, pp. 306–315, 2008. Sridhar, Srinivas This event is cosponsored by the Central New England Chapter of the IEEE Lasers and Electro-Optics Society as part of the LEOS 30 th Anniversary Celebration Journal Article In: 2007. Selvarasah, S; Chao, SH; Chen, C-L; Mao, D; Hopwood, J; Ryley, S; Sridhar, S; Khademhosseini, A; Busnaina, A; Dokmeci, MR A high aspect ratio, flexible, transparent and low-cost parylene-C shadow mask technology for micropatterning applications Proceedings Article In: TRANSDUCERS 2007-2007 International Solid-State Sensors, Actuators and Microsystems Conference, pp. 533–536, IEEE 2007. Selvarasah, Selvapraba; Makaram, Prashanth; Chen, Chia-Ling; Xiong, Xugang; Chao, Shih-Hsien; Busnaina, Ahmed; Sridhar, Srinivas; Dokmeci, Mehmet R A three dimensional multi-walled carbon nanotube based thermal sensor on a flexible parylene substrate Proceedings Article In: 2007 7th IEEE Conference on Nanotechnology (IEEE NANO), pp. 1062–1066, IEEE 2007. Parikh, A; Yarbrough, W; Mason, M; Sridhar, S; Chidambaram, PR; Cai, Z Characterization of structure and morphology of an advanced p-channel field effect transistor under uniaxial stress by synchrotron x-ray diffraction Journal Article In: Applied physics letters, vol. 90, no. 17, pp. 172117, 2007. Tags: Sensors Sridhar, S; Giannakopoulos, AE; Suresh, S; Ramamurty, U CONDENSED MATTER: Dielectric and Optical Properties (PACS 77-79)-Electrical response during indentation of piezoelectric materials: A new method for material characterization Journal Article In: Journal of Applied Physics, vol. 85, no. 1, pp. 380–387, 1999. Tags: Sensors Selvarasah, S; Banyal, R; Casse, BDF; Lu, WT; Sridhar, S; Dokmeci, MR Design and implementation of silicon-based optical nanostructures for integrated photonic circuit applications using Deep Reactive Ion Etching (DRIE) technique Journal Article In: 0000.@misc{faegh2018sensor,
title = {Sensor system utilizing piezoelectric microcantilever coupled with resonating circuit},
author = {Samira Faegh and Nader Jalili and Srinivas Sridhar},
year = {2018},
date = {2018-00-01},
abstract = {An interchangeable sensor system is described, including: a microcantilever including a beam anchored at a first end, the beam being free to vibrate on another end, wherein a piezoelectric layer is deposited on a surface of the beam; an input configured to receive a voltage from a voltage source for applying voltage to the piezoelectric layer; and a resonating circuit including: the piezoelectric layer, configured as a capacitor of the resonant circuit; and one or more additional electrical elements; wherein the voltage source is configured to apply a first AC voltage under a first condition for actuating the microcantilever at a first mechanical resonating frequency of the microcantilever and a second AC voltage under a second condition for actuating the microcantilever at a second electrical resonating frequency of the resonating circuit. Method of using the sensor system is also described.},
note = {US Patent 9,921,226},
keywords = {Sensors},
pubstate = {published},
tppubtype = {misc}
}
@article{ozturk2015novel,
title = {A novel coupled resonator photonic crystal design in lithium niobate for electrooptic applications},
author = {Birol Ozturk and Ozgur Yavuzcetin and Srinivas Sridhar},
year = {2015},
date = {2015-01-01},
journal = {International Journal of Optics},
volume = {2015},
publisher = {Hindawi},
abstract = {High-aspect-ratio photonic crystal air-hole fabrication on bulk Lithium Niobate (LN) substrates is extremely difficult due to its inherent resistance to etching, resulting in conical structures and high insertion losses. Here, we propose a novel coupled resonator photonic crystal (CRPC) design, combining a coupled resonator approach with that of Bragg gratings. CRPC design parameters were optimized by analytical calculations and FDTD simulations. CRPC structures with optimized parameters were fabricated and electrooptically tested on bulk LN annealed proton exchange waveguides. Low insertion loss and large electrooptic effect were observed with the fabricated devices, making the CRPC design a promising structure for electrooptic device applications.},
keywords = {Nanomedicine, Sensors},
pubstate = {published},
tppubtype = {article}
}
@article{faegh2014ultrasensitive,
title = {Ultrasensitive piezoelectric-based microcantilever biosensor: Theory and experiment},
author = {Samira Faegh and Nader Jalili and Srinivas Sridhar},
year = {2014},
date = {2014-01-01},
journal = {IEEE/ASME Transactions on Mechatronics},
volume = {20},
number = {1},
pages = {308--312},
publisher = {IEEE},
abstract = {Microcantilever (MC)-based sensors have become an advantageous tool for detection of ultrasmall masses and biological species. Exploiting high affinity of biomolecules, MCs offer a simple, inexpensive, and highly sensitive platform for high throughput diagnosis and analytical sensing. A number of methods have been reported targeting sensitivity enhancement of MC-based systems including geometry modification, employing nanoparticle-enhanced MCs, and operating MCs in lateral and torsional modes. High mode resonating MCs have been reported as a promising sensitivity enhancement method. Although being investigated, there have not been enough analytical high fidelity models describing all dynamics and behavior of MCs operating in high modes with experimental proof. In this study, experimental results of a piezoelectric self-sensing MC operating as a biological sensor at ultrahigh mode along with theoretical verification are presented. Effect of absorbed mass on the frequency shift was investigated using self-sensing and optical measurement methodologies. Mode convergence theory was adopted in order to get the best estimation of resonance frequencies at different modes. Amino groups of aminothenethaiol solution are immobilized over MC. Shift in resonance frequencies in higher modes are measured and the quality factor is calculated proving the fact that sensitivity of MC to detect absorbed masses enhances as the number of modes increases.},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
@article{yavuzcetin2013fabrication,
title = {Fabrication and characterization of single mode annealed proton exchanged waveguides in-x-cut lithium niobate},
author = {O Yavuzcetin and Nicholas R Perry and Sean T Malley and Rebecca L Dally and Herman P Novikov and Birol Ozturk and Srinivas Sridhar},
year = {2013},
date = {2013-01-01},
journal = {Optical Materials},
volume = {36},
number = {2},
pages = {372--375},
publisher = {North-Holland},
abstract = {Lithium niobate is a key, well-known material in optical communication that maintains its importance due to its high speed in electro-optical modulators and other optical devices. Using a benzoic acid proton exchange method and annealing in wet O2, we have fabricated waveguides along the y-axis of -x-cut lithium niobate substrate. We have optimized proton exchange and annealing time to make waveguides with the highest transmission we observed to date. The optical transmission was measured in waveguides between 3 μm and 7 μm in width, and 10 mm in length. The near-field mode properties of the waveguides were also examined. In addition, we discovered that the transmission through waveguides is reduced by the surface residues which are underestimated in most fabrication processes. This paper outlines the full fabrication process as well as characterization methods in detail, including a supercontinuum laser source.},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
@article{faegh2013cost,
title = {A cost-effective self-sensing biosensor for detection of biological species at ultralow concentrations},
author = {Samira Faegh and Nader Jalili and Ozgur Yavuzcetin and Dattatri Nagesha and Rajiv Kumar and Srinivas Sridhar},
year = {2013},
date = {2013-01-01},
journal = {Journal of Applied Physics},
volume = {113},
number = {22},
pages = {224905},
publisher = {American Institute of Physics},
abstract = {Detection of ultrasmall masses and identification of biological molecules have been made possible as a result of advances in nanotechnology. Development of biosensing tools has significantly contributed to high-throughput diagnosis and analytical sensing exploiting high affinity of biomolecules. MicroCantilever (MC)-based detection has emerged as a promising biosensing tool for offering label-free and cost-effective sensing capabilities. One of the main criteria determining the success of each biosensor is the capability of the sensing platform to operate in aqueous media. Although being characterized with high sensitivity and simplicity, MCs do not provide an effective tool for measurement of marker proteins in liquid media due to large hydrodynamic damping and losses in the surrounding liquid. In this study, we describe two approaches to high sensitivity biomolecular detection using piezoelectric microcantilevers. (i) Immobilized Mass Detection in Air using electro-mechanical resonance: a unique self-sensing measurement technique is reported utilizing a self-sensing circuit consisting of a piezoelectric MC to address the mentioned limitation. The capability of the self-sensing measurement technique was first verified by detecting ultrasmall biological masses immobilized over the surface of MC by monitoring the shift in fundamental mechanical resonance frequency of the system in air and comparing it with optical-based measurement. This was further utilized for calibration of mass detection in liquid media. (ii) Immobilized Mass Detection in Liquid using the electrical self-sensing circuit's resonance: Once the capability to detect adsorbed mass was verified, the self-sensing platform was implemented to detect different concentrations of target molecule (glucose in this study) in liquid media by adopting the highly sensitive resonance frequency of the whole circuit instead of the mechanical response of MC. Molecular binding occurring over the surface of MC changes the capacitance of the total interface thus changing the resonance frequency of the circuit. The amount of shift in the measured circuit's resonance frequency provides qualitative and quantitative insight into the amount of target protein concentration. The reported diagnostic platform offers a simple, cost-effective, all-electronics method of detection where the need for any bulky, expensive optical based measurement is eliminated. Utilizing this technique, physiological concentration of glucose as low as 500 nM was measured in liquid media. This sensitivity is significantly higher than what has been previously reported using other mechanical resonance techniques.},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
@article{faegh2013self,
title = {A self-sensing piezoelectric microcantilever biosensor for detection of ultrasmall adsorbed masses: theory and experiments},
author = {Samira Faegh and Nader Jalili and Srinivas Sridhar},
year = {2013},
date = {2013-01-01},
urldate = {2013-01-01},
journal = {Sensors},
volume = {13},
number = {5},
pages = {6089--6108},
publisher = {Multidisciplinary Digital Publishing Institute},
abstract = {Detection of ultrasmall masses such as proteins and pathogens has been made possible as a result of advancements in nanotechnology. Development of label-free and highly sensitive biosensors has enabled the transduction of molecular recognition into detectable physical quantities. Microcantilever (MC)-based systems have played a widespread role in developing such biosensors. One of the most important drawbacks of all of the available biosensors is that they all come at a very high cost. Moreover, there are certain limitations in the measurement equipments attached to the biosensors which are mostly optical measurement systems. A unique self-sensing detection technique is proposed in this paper in order to address most of the limitations of the current measurement systems. A self-sensing bridge is used to excite piezoelectric MC-based sensor functioning in dynamic mode, which simultaneously measures the system’s response through the self-induced voltage generated in the piezoelectric material. As a result, the need for bulky, expensive read-out equipment is eliminated. A comprehensive mathematical model is presented for the proposed self-sensing detection platform using distributed-parameters system modeling. An adaptation strategy is then implemented in the second part in order to compensate for the time-variation of piezoelectric properties which dynamically improves the behavior of the system. Finally, results are reported from an extensive experimental investigation carried out to prove the capability of the proposed platform. Experimental results verified the proposed mathematical modeling presented in the first part of the study with accuracy of 97.48%. Implementing the adaptation strategy increased the accuracy to 99.82%. These results proved the measurement capability of the proposed self-sensing strategy. It enables development of a cost-effective, sensitive and miniaturized mass sensing platform.
Keywords: microcantilever; biosensor; distributed-parameter modeling; mass detection},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
Keywords: microcantilever; biosensor; distributed-parameter modeling; mass detection@article{yavuzcetin2012photonic,
title = {Photonic crystal fabrication in lithium niobate via pattern transfer through wet and dry etched chromium mask},
author = {Ozgur Yavuzcetin and Herman P Novikov and Rebecca L Dally and Sean T Malley and Nicholas R Perry and Birol Ozturk and Srinivas Sridhar},
year = {2012},
date = {2012-01-01},
journal = {Journal of Applied Physics},
volume = {112},
number = {7},
pages = {074303},
publisher = {American Institute of Physics},
abstract = {The need to fabricate photonic crystals from lithium niobate (LN) with accurate feature sizes is important to the development of optoelectronic devices. This paper reports a fabrication process to dry etch X-cut LN at a submicron scale using electron beam lithography and chromium as a hard mask. The chromium mask was used for both dry-etching and wet-etching in a unique method. Problems and solutions found during fabrication are presented. Arrays consisting of 400 nm diameter holes with a high aspect ratio were etched in LN, creating photonic crystals modeled to transmit light in the infrared spectrum.},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
@misc{sridhar2011large,
title = {Large scale nanoelement assembly method for making nanoscale circuit interconnects and diodes},
author = {Srinivas Sridhar and Evin Gultepe and Dattatri Nagesha},
year = {2011},
date = {2011-02-01},
abstract = {Nanoelements such as single walled carbon nanotubes are assembled in three dimensions into a nanoscale template on a substrate by means of electrophoresis and dielectrophoresis at ambient temperature. The current-voltage relation indicates that strong substrate-nanotube interconnects carrying mA currents are established inside the template pores. The method is suitable for large-scale, rapid, three-dimensional assembly of 1,000,000 nanotubes per square centimeter area using mild conditions. Circuit interconnects made by the method can be used for nanoscale electronics applications.},
note = {US Patent App. 12/936,938},
keywords = {Sensors},
pubstate = {published},
tppubtype = {misc}
}
@article{yavuzcetin2011conicity,
title = {Conicity and depth effects on the optical transmission of lithium niobate photonic crystals patterned by focused ion beam},
author = {Ozgur Yavuzcetin and Birol Ozturk and Dong Xiao and Srinivas Sridhar},
year = {2011},
date = {2011-01-01},
journal = {Optical Materials Express},
volume = {1},
number = {7},
pages = {1262--1271},
publisher = {Optical Society of America},
abstract = {We report on novel focused ion beam fabrication techniques that can greatly improve the optical performance of photonic crystal structures. The finite depth and conicity effects of holes and trenches in Lithium Niobate (LN) photonic crystals have been theoretically analyzed, showing that the conicity causes refraction into the bulk sample, resulting in high transmission loss and no useful spectral features. The techniques for reducing the conicity angle from 25° to 5° were explained for the focused ion beam (FIB) milled structures.
©2011 Optical Society of America},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
©2011 Optical Society of America@article{selvarasah2008reusable,
title = {A reusable high aspect ratio parylene-C shadow mask technology for diverse micropatterning applications},
author = {S Selvarasah and SH Chao and C-L Chen and S Sridhar and A Busnaina and A Khademhosseini and MR Dokmeci},
year = {2008},
date = {2008-01-01},
journal = {Sensors and Actuators A: Physical},
volume = {145},
pages = {306--315},
publisher = {Elsevier},
abstract = {In this paper, we present a low cost, flexible and reusable parylene-C shadow mask technology for diverse micropatterning applications. The smallest feature size of 4 μm is demonstrated and the technology is scalable up to full wafer scale. With the addition of SU-8 pillars, we also demonstrate multimask processing with an alignment accuracy of about 4–9 μm. To achieve features with fine resolution, a low temperature and high aspect ratio (>8:1) parylene etch process is also developed. Utilizing this shadow mask, we successfully patterned proteins and cells on various surfaces (glass, PDMS, methacrylate). High pattern flexibility (structures with different shapes and dimensions are successfully patterned) and patterning on curved PDMS surfaces are also demonstrated. This technology has potential applications for patterning proteins, cells and organic transistors on conventional and/or unconventional substrates.},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
@article{sridharevent,
title = {This event is cosponsored by the Central New England Chapter of the IEEE Lasers and Electro-Optics Society as part of the LEOS 30 th Anniversary Celebration},
author = {Srinivas Sridhar},
year = {2007},
date = {2007-05-16},
abstract = {We discuss negative refraction at microwave and optical frequencies in 1D and 2D metallic and dielectric photonic crystal media. Here negative refraction is due to the anomalous dispersion characteristics of the medium. In negative index media, the fields and the wavevector obey a left-handed relationship. The experiments show that materials with tailor-made negative or positive refractive indices over broad spectral ranges can be designed and fabricated. We have also demonstrated that negative refraction leads to some novel optical elements for imaging, such as flat lenses and focusing by plano concave lenses. A general theory of imaging by a flat lens without optical axis has been developed, leading to specification of the characteristics required of the flat lens metamaterial. Features of images formed using negatively refracting optical elements, including sub-wavelength resolution, are discussed. Potential …},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
@inproceedings{selvarasah2007high,
title = {A high aspect ratio, flexible, transparent and low-cost parylene-C shadow mask technology for micropatterning applications},
author = {S Selvarasah and SH Chao and C-L Chen and D Mao and J Hopwood and S Ryley and S Sridhar and A Khademhosseini and A Busnaina and MR Dokmeci},
year = {2007},
date = {2007-01-01},
booktitle = {TRANSDUCERS 2007-2007 International Solid-State Sensors, Actuators and Microsystems Conference},
pages = {533--536},
organization = {IEEE},
abstract = {In this paper, we present a flexible parylene-C shadow mask technology for creating microscale patterns on flat and curved surfaces. The smallest feature size of 4 μm is demonstrated and the technology is scalable up to full wafer size. With the addition of SU-8 pillars, we also demonstrate multi mask processing with an alignment accuracy of about 5-6 μm. To achieve the smallest features, a low temperature and high aspect ratio (>8:1) parylene etch process is also developed. Utilizing this shadow mask, we successfully patterned proteins and cells on various surfaces (glass, PDMS, methacrylate) up to 9 times. This technology has potential applications for patterning proteins, cells and organic transistors on conventional and/or unconventional substrates.},
keywords = {Sensors},
pubstate = {published},
tppubtype = {inproceedings}
}
@inproceedings{selvarasah2007three,
title = {A three dimensional multi-walled carbon nanotube based thermal sensor on a flexible parylene substrate},
author = {Selvapraba Selvarasah and Prashanth Makaram and Chia-Ling Chen and Xugang Xiong and Shih-Hsien Chao and Ahmed Busnaina and Srinivas Sridhar and Mehmet R Dokmeci},
year = {2007},
date = {2007-01-01},
booktitle = {2007 7th IEEE Conference on Nanotechnology (IEEE NANO)},
pages = {1062--1066},
organization = {IEEE},
abstract = {In this paper, we present a flexible parylene-C shadow mask technology for creating microscale patterns on flat and curved surfaces. The smallest feature size of 4 μm is demonstrated and the technology is scalable up to full wafer size. With the addition of SU-8 pillars, we also demonstrate multi mask processing with an alignment accuracy of about 5-6 μm. To achieve the smallest features, a low temperature and high aspect ratio (>8:1) parylene etch process is also developed. Utilizing this shadow mask, we successfully patterned proteins and cells on various surfaces (glass, PDMS, methacrylate) up to 9 times. This technology has potential applications for patterning proteins, cells and organic transistors on conventional and/or unconventional substrates.},
keywords = {Sensors},
pubstate = {published},
tppubtype = {inproceedings}
}
@article{parikh2007characterization,
title = {Characterization of structure and morphology of an advanced p-channel field effect transistor under uniaxial stress by synchrotron x-ray diffraction},
author = {A Parikh and W Yarbrough and M Mason and S Sridhar and PR Chidambaram and Z Cai},
year = {2007},
date = {2007-01-01},
journal = {Applied physics letters},
volume = {90},
number = {17},
pages = {172117},
publisher = {American Institute of Physics},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
@article{sridhar1999condensed,
title = {CONDENSED MATTER: Dielectric and Optical Properties (PACS 77-79)-Electrical response during indentation of piezoelectric materials: A new method for material characterization},
author = {S Sridhar and AE Giannakopoulos and S Suresh and U Ramamurty},
year = {1999},
date = {1999-01-01},
journal = {Journal of Applied Physics},
volume = {85},
number = {1},
pages = {380--387},
publisher = {New York, NY: American Institute of Physics, c1937-},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
@article{selvarasahdesign,
title = {Design and implementation of silicon-based optical nanostructures for integrated photonic circuit applications using Deep Reactive Ion Etching (DRIE) technique},
author = {S Selvarasah and R Banyal and BDF Casse and WT Lu and S Sridhar and MR Dokmeci},
abstract = {In this paper, we present the fabrication of nano optical elements by means of deep reactive ion etching technique (Bosch process) on a silicon-on-insulator substrate. The nano structures are fabricated in a two step process. The first step consists of direct-writing nanoscale patterns on PMMA polymer by electron beam lithography. These nano patterns are then transferred to the silicon surface by a low temperature and low pressure deep reactive ion etching (DRIE) process using PMMA as a mask. The low temperature and low pressure conditions in the DRIE process minimize scalloping in the nanoscale features. We found that the etch rate is highly dependent on the aspect ratio of the structure. We have used the DRIE method to fabricate a negative-index photonic crystal flat lens and demonstrated the focusing properties of this flat lens using a near-field scanning optical microscope.},
keywords = {Sensors},
pubstate = {published},
tppubtype = {article}
}
