Nanoapertures milled in metallic films called zero-mode waveguides (ZMWs) overcome the limitation... more Nanoapertures milled in metallic films called zero-mode waveguides (ZMWs) overcome the limitations of classical confocal microscopes by enabling single molecule analysis at micromolar concentrations with improved fluorescence brightness.
The vast majority of proteins are intrinsically fluorescent in the ultraviolet, thanks to the emi... more The vast majority of proteins are intrinsically fluorescent in the ultraviolet, thanks to the emission from their tryptophan and tyrosine amino-acid constituents. However, the protein autofluorescence quantum yields are generally very low due to the prevailing quenching mechanisms by other amino acids inside the protein. This motivates the interest to enhance the radiative emission rate of proteins using nanophotonic structures. Although there have been numerous reports of Purcell effect and local density of optical states control in the visible range using single dipole quantum emitters, the question remains open to apply these concepts in the UV on real proteins containing several tryptophan and tyrosine amino acids arranged in a highly complex manner. Here, we report the first complete characterization of the Purcell effect and radiative rate enhancement for the UV intrinsic fluorescence of label-free β-galactosidase and streptavidin proteins in plasmonic aluminum nanoapertures. ...
Extending plasmonics into the ultraviolet range imposes the use of aluminum to achieve the best o... more Extending plasmonics into the ultraviolet range imposes the use of aluminum to achieve the best optical performance. However, water corrosion is a major limiting issue for UV aluminum plasmonics, as this phenomenon occurs significantly faster in presence of UV light, even at low laser powers of a few microwatts. Here we assess the performance of nanometer-thick layers of various metal oxides deposited by atomic layer deposition (ALD) and plasma-enhanced chemical vapor deposition (PECVD) on top of aluminum nanoapertures to protect the metal against UV photocorrosion. The combination of a 5 nm Al2O3 layer covered by a 5 nm TiO2 capping provides the best resistance performance, while a single 10 nm layer of SiO2 or HfO2 is a good alternative. We also report the influence of the laser wavelength, the laser operation mode and the pH of the solution. Properly choosing these conditions significantly extends the range of optical powers for which the aluminum nanostructures can be used. As a...
Single photon sources with high brightness and subnanosecond lifetimes are key components for qua... more Single photon sources with high brightness and subnanosecond lifetimes are key components for quantum technologies. Optical nanoantennas can enhance the emission properties of single quantum emitters, but this approach requires accurate nanoscale positioning of the source at the plasmonic hotspot. Here, we use plasmonic nanoantennas to simultaneously trap single colloidal quantum dots and enhance their photoluminescence. The nano-optical trapping automatically locates the quantum emitter at the nanoantenna hotspot without further processing. Our dedicated nanoantenna design achieves a high trap stiffness of 0.6 (fN/nm)/mW for quantum dot trapping, together with a relatively low trapping power of 2 mW/μm2. The emission from the nanoantenna-trapped single quantum dot shows 7× increased brightness, 50× reduced blinking, 2× shortened lifetime, and a clear antibunching below 0.5 demonstrating true single photon emission. Combining nano-optical tweezers with plasmonic enhancement is a pro...
Nanoparticles (NPs) with different geometry have been extensively inquired for decades owing to t... more Nanoparticles (NPs) with different geometry have been extensively inquired for decades owing to their unique optical properties which provide efficient focusing, absorption, scattering, waveguiding and directivity at the nanoscale. The development of an efficient photonic device requires good antenna, as well as resonator properties, that is where hybrid metal-semiconductor nanostructure comes in to play. This work is devoted to the numerical modeling of the optical properties of GaP nanowire (NW) with Ga plasmonic droplet. The modeling results demonstrate that such a self-assembled hybrid nanostructure provides polarization switchable focusing of light at the metal-semiconductor interface, effective beam steering, and emission confinement. Numerical simulation estimates that the field can be focused tenfold at the metal-semiconductor interface providing pathway for excitation of the quantum emitter or hot electron injection. The hybrid structure can also be used to turn the light efficiently without the need to bend the NW acting as a waveguide providing 4 times more efficient 90°beam steering compare to the NW without the Ga NP. We demonstrate that the light intensity varies 16 times at the interface for S and P polarization which can be utilized for optical switching in photonic or data processing applications. In the end we discuss the architecture of the devices for the future applications based on the investigated hybrid structure.
—This paper presents a simulated design of millimeter wave square patch antenna 1X6 array on sili... more —This paper presents a simulated design of millimeter wave square patch antenna 1X6 array on silicon and Roger RO4003 substrate for prominent multiple bands i.e. 58GHz-60GHz, 65GHz-68GHz, 72GHz-77GHz.Designed antenna can serve 5G cellular network as well as advance device-to-device (D2D) network which is special feature of 5G communication system to reduce end-to-end latency and to implement Mission Critical Push-To-Talk Communication (MCPTT) and Vehicle-to-Anything (V2X) Communication. Designed antenna has peakgain of 9 dB and very high efficiency. Return loss for given bands at their resonant frequencies are as low as-35dB and total bandwidth of 9.57 GHz. Silicon is used under feeding network to enhance the bandwidth and reduce the size of feeding network and low dielectric material under patch to reduce dielectric loss thus maintaining the efficiency. Symmetrical parallel feeding network is used to enhance gain. Inset fed with quarter wave transformers are used for feeding and matching, along with maintaining the conformity. A novel design is used to kill the spurious radiation due to feed network, thus shaping the radiation pattern for cellular application. Overall size of antenna is 6.7mmX30mmX1.2mm compatible with miniaturized devices and is printable. 1
This paper presents a simulated design of high
performance elliptical ring Microstrip patch anten... more This paper presents a simulated design of high performance elliptical ring Microstrip patch antenna at resonant frequency of 8 GHz for radar. Owing to its intrinsic geometry elliptical ring patch is found to be suitable candidate for designing high power, large gain and better efficiency conformal antennas for radar at X-band or even higher frequencies. Simulated antenna shows very high average gain of 7.5 dB for entire bandwidth of 340MHz i.e. 4.25% impedance bandwidth. Simulated results shows very good return loss performance, S11 parameter is -42.5 dB at resonant frequency. Roger Ultralam 2000 substrate is used to design the antenna. Average radiation efficiency of antenna is very high (97.9%). Design show great promise for radar application with no side lobes, high directivity of 7.71 dB at 8 GHz & very high front to back ratio. Comparative study of recent works in X-Band and our design is presented & variation of return loss with dielectric height is also elaborated in paper.
This paper presents design and simulation of wide
band elliptical ring patch antenna with arc tru... more This paper presents design and simulation of wide band elliptical ring patch antenna with arc truncation in K-band for mobile communication application. Elliptical ring’s intrinsic geometry leads to single feed circular polarization and high radiation efficiency so making it suitable for implementing on array and as well as for practical application were low losses are salient features. Antenna have large bandwidth and circular polarization at resonant frequency of 19.8 GHz and is suitable for satellite to mobile high speed communication were large free spectrum is required which is unavailable at lower frequencies. In K-band simulated results shows 20% impedance bandwidth and 110 MHz circular polarization band. Parametric study of antenna’s figure of merit i.e. return loss and axial ratio with radius of truncating circle is also illustrated.
Abstract- X-band is most important band for Radar, but existing radar antennas are bulky and lowe... more Abstract- X-band is most important band for Radar, but existing radar antennas are bulky and lower on mobility parameter, thus need a separate vehicle to carry. Radar antennas also suffer polarization mismatch loss leading to poor detection. This paper presents a simulated design of high performance, low profile patch antenna for X-band radar to mitigate the problem of portability as well as polarization mismatch loss. Elliptical patch has been used because of its intrinsic geometry it is found to be suitable candidate for designing high power, large gain and high efficiency conformal antennas for radar at X-band or even higher frequencies. Simulated antenna shows very high average gain of 7.5 dB for entire bandwidth of 600 MHz i.e. 7.41% impedance bandwidth. Axial Ratio is as low as 1.64 and shows circular polarization for 140 MHz bandwidth. Simulated results show very good return loss performance, S11 parameter is -36 dB and VSWR is 1.03 at resonant frequency. Roger Ultralam 2000 substrate is used to design the antenna. Average radiation efficiency of antenna is very high (97.9%). Design show great promise for radar and military satellite communication since no side lobes, high directivity of 7.71 dB for 8.1 GHz & very high front to back ratio. Comparative study of recent works in X-Band and our design is also presented.
Nanoapertures milled in metallic films called zero-mode waveguides (ZMWs) overcome the limitation... more Nanoapertures milled in metallic films called zero-mode waveguides (ZMWs) overcome the limitations of classical confocal microscopes by enabling single molecule analysis at micromolar concentrations with improved fluorescence brightness.
The vast majority of proteins are intrinsically fluorescent in the ultraviolet, thanks to the emi... more The vast majority of proteins are intrinsically fluorescent in the ultraviolet, thanks to the emission from their tryptophan and tyrosine amino-acid constituents. However, the protein autofluorescence quantum yields are generally very low due to the prevailing quenching mechanisms by other amino acids inside the protein. This motivates the interest to enhance the radiative emission rate of proteins using nanophotonic structures. Although there have been numerous reports of Purcell effect and local density of optical states control in the visible range using single dipole quantum emitters, the question remains open to apply these concepts in the UV on real proteins containing several tryptophan and tyrosine amino acids arranged in a highly complex manner. Here, we report the first complete characterization of the Purcell effect and radiative rate enhancement for the UV intrinsic fluorescence of label-free β-galactosidase and streptavidin proteins in plasmonic aluminum nanoapertures. ...
Extending plasmonics into the ultraviolet range imposes the use of aluminum to achieve the best o... more Extending plasmonics into the ultraviolet range imposes the use of aluminum to achieve the best optical performance. However, water corrosion is a major limiting issue for UV aluminum plasmonics, as this phenomenon occurs significantly faster in presence of UV light, even at low laser powers of a few microwatts. Here we assess the performance of nanometer-thick layers of various metal oxides deposited by atomic layer deposition (ALD) and plasma-enhanced chemical vapor deposition (PECVD) on top of aluminum nanoapertures to protect the metal against UV photocorrosion. The combination of a 5 nm Al2O3 layer covered by a 5 nm TiO2 capping provides the best resistance performance, while a single 10 nm layer of SiO2 or HfO2 is a good alternative. We also report the influence of the laser wavelength, the laser operation mode and the pH of the solution. Properly choosing these conditions significantly extends the range of optical powers for which the aluminum nanostructures can be used. As a...
Single photon sources with high brightness and subnanosecond lifetimes are key components for qua... more Single photon sources with high brightness and subnanosecond lifetimes are key components for quantum technologies. Optical nanoantennas can enhance the emission properties of single quantum emitters, but this approach requires accurate nanoscale positioning of the source at the plasmonic hotspot. Here, we use plasmonic nanoantennas to simultaneously trap single colloidal quantum dots and enhance their photoluminescence. The nano-optical trapping automatically locates the quantum emitter at the nanoantenna hotspot without further processing. Our dedicated nanoantenna design achieves a high trap stiffness of 0.6 (fN/nm)/mW for quantum dot trapping, together with a relatively low trapping power of 2 mW/μm2. The emission from the nanoantenna-trapped single quantum dot shows 7× increased brightness, 50× reduced blinking, 2× shortened lifetime, and a clear antibunching below 0.5 demonstrating true single photon emission. Combining nano-optical tweezers with plasmonic enhancement is a pro...
Nanoparticles (NPs) with different geometry have been extensively inquired for decades owing to t... more Nanoparticles (NPs) with different geometry have been extensively inquired for decades owing to their unique optical properties which provide efficient focusing, absorption, scattering, waveguiding and directivity at the nanoscale. The development of an efficient photonic device requires good antenna, as well as resonator properties, that is where hybrid metal-semiconductor nanostructure comes in to play. This work is devoted to the numerical modeling of the optical properties of GaP nanowire (NW) with Ga plasmonic droplet. The modeling results demonstrate that such a self-assembled hybrid nanostructure provides polarization switchable focusing of light at the metal-semiconductor interface, effective beam steering, and emission confinement. Numerical simulation estimates that the field can be focused tenfold at the metal-semiconductor interface providing pathway for excitation of the quantum emitter or hot electron injection. The hybrid structure can also be used to turn the light efficiently without the need to bend the NW acting as a waveguide providing 4 times more efficient 90°beam steering compare to the NW without the Ga NP. We demonstrate that the light intensity varies 16 times at the interface for S and P polarization which can be utilized for optical switching in photonic or data processing applications. In the end we discuss the architecture of the devices for the future applications based on the investigated hybrid structure.
—This paper presents a simulated design of millimeter wave square patch antenna 1X6 array on sili... more —This paper presents a simulated design of millimeter wave square patch antenna 1X6 array on silicon and Roger RO4003 substrate for prominent multiple bands i.e. 58GHz-60GHz, 65GHz-68GHz, 72GHz-77GHz.Designed antenna can serve 5G cellular network as well as advance device-to-device (D2D) network which is special feature of 5G communication system to reduce end-to-end latency and to implement Mission Critical Push-To-Talk Communication (MCPTT) and Vehicle-to-Anything (V2X) Communication. Designed antenna has peakgain of 9 dB and very high efficiency. Return loss for given bands at their resonant frequencies are as low as-35dB and total bandwidth of 9.57 GHz. Silicon is used under feeding network to enhance the bandwidth and reduce the size of feeding network and low dielectric material under patch to reduce dielectric loss thus maintaining the efficiency. Symmetrical parallel feeding network is used to enhance gain. Inset fed with quarter wave transformers are used for feeding and matching, along with maintaining the conformity. A novel design is used to kill the spurious radiation due to feed network, thus shaping the radiation pattern for cellular application. Overall size of antenna is 6.7mmX30mmX1.2mm compatible with miniaturized devices and is printable. 1
This paper presents a simulated design of high
performance elliptical ring Microstrip patch anten... more This paper presents a simulated design of high performance elliptical ring Microstrip patch antenna at resonant frequency of 8 GHz for radar. Owing to its intrinsic geometry elliptical ring patch is found to be suitable candidate for designing high power, large gain and better efficiency conformal antennas for radar at X-band or even higher frequencies. Simulated antenna shows very high average gain of 7.5 dB for entire bandwidth of 340MHz i.e. 4.25% impedance bandwidth. Simulated results shows very good return loss performance, S11 parameter is -42.5 dB at resonant frequency. Roger Ultralam 2000 substrate is used to design the antenna. Average radiation efficiency of antenna is very high (97.9%). Design show great promise for radar application with no side lobes, high directivity of 7.71 dB at 8 GHz & very high front to back ratio. Comparative study of recent works in X-Band and our design is presented & variation of return loss with dielectric height is also elaborated in paper.
This paper presents design and simulation of wide
band elliptical ring patch antenna with arc tru... more This paper presents design and simulation of wide band elliptical ring patch antenna with arc truncation in K-band for mobile communication application. Elliptical ring’s intrinsic geometry leads to single feed circular polarization and high radiation efficiency so making it suitable for implementing on array and as well as for practical application were low losses are salient features. Antenna have large bandwidth and circular polarization at resonant frequency of 19.8 GHz and is suitable for satellite to mobile high speed communication were large free spectrum is required which is unavailable at lower frequencies. In K-band simulated results shows 20% impedance bandwidth and 110 MHz circular polarization band. Parametric study of antenna’s figure of merit i.e. return loss and axial ratio with radius of truncating circle is also illustrated.
Abstract- X-band is most important band for Radar, but existing radar antennas are bulky and lowe... more Abstract- X-band is most important band for Radar, but existing radar antennas are bulky and lower on mobility parameter, thus need a separate vehicle to carry. Radar antennas also suffer polarization mismatch loss leading to poor detection. This paper presents a simulated design of high performance, low profile patch antenna for X-band radar to mitigate the problem of portability as well as polarization mismatch loss. Elliptical patch has been used because of its intrinsic geometry it is found to be suitable candidate for designing high power, large gain and high efficiency conformal antennas for radar at X-band or even higher frequencies. Simulated antenna shows very high average gain of 7.5 dB for entire bandwidth of 600 MHz i.e. 7.41% impedance bandwidth. Axial Ratio is as low as 1.64 and shows circular polarization for 140 MHz bandwidth. Simulated results show very good return loss performance, S11 parameter is -36 dB and VSWR is 1.03 at resonant frequency. Roger Ultralam 2000 substrate is used to design the antenna. Average radiation efficiency of antenna is very high (97.9%). Design show great promise for radar and military satellite communication since no side lobes, high directivity of 7.71 dB for 8.1 GHz & very high front to back ratio. Comparative study of recent works in X-Band and our design is also presented.
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Papers by prithu roy
performance elliptical ring Microstrip patch antenna at
resonant frequency of 8 GHz for radar. Owing to its intrinsic
geometry elliptical ring patch is found to be suitable candidate
for designing high power, large gain and better efficiency
conformal antennas for radar at X-band or even higher
frequencies. Simulated antenna shows very high average gain of
7.5 dB for entire bandwidth of 340MHz i.e. 4.25% impedance
bandwidth. Simulated results shows very good return loss
performance, S11 parameter is -42.5 dB at resonant frequency.
Roger Ultralam 2000 substrate is used to design the antenna.
Average radiation efficiency of antenna is very high (97.9%).
Design show great promise for radar application with no side
lobes, high directivity of 7.71 dB at 8 GHz & very high front to
back ratio. Comparative study of recent works in X-Band and
our design is presented & variation of return loss with dielectric
height is also elaborated in paper.
band elliptical ring patch antenna with arc truncation in K-band
for mobile communication application. Elliptical ring’s intrinsic
geometry leads to single feed circular polarization and high
radiation efficiency so making it suitable for implementing on
array and as well as for practical application were low losses are
salient features. Antenna have large bandwidth and circular
polarization at resonant frequency of 19.8 GHz and is suitable
for satellite to mobile high speed communication were large free
spectrum is required which is unavailable at lower frequencies.
In K-band simulated results shows 20% impedance bandwidth
and 110 MHz circular polarization band. Parametric study of
antenna’s figure of merit i.e. return loss and axial ratio with
radius of truncating circle is also illustrated.
Drafts by prithu roy
performance elliptical ring Microstrip patch antenna at
resonant frequency of 8 GHz for radar. Owing to its intrinsic
geometry elliptical ring patch is found to be suitable candidate
for designing high power, large gain and better efficiency
conformal antennas for radar at X-band or even higher
frequencies. Simulated antenna shows very high average gain of
7.5 dB for entire bandwidth of 340MHz i.e. 4.25% impedance
bandwidth. Simulated results shows very good return loss
performance, S11 parameter is -42.5 dB at resonant frequency.
Roger Ultralam 2000 substrate is used to design the antenna.
Average radiation efficiency of antenna is very high (97.9%).
Design show great promise for radar application with no side
lobes, high directivity of 7.71 dB at 8 GHz & very high front to
back ratio. Comparative study of recent works in X-Band and
our design is presented & variation of return loss with dielectric
height is also elaborated in paper.
band elliptical ring patch antenna with arc truncation in K-band
for mobile communication application. Elliptical ring’s intrinsic
geometry leads to single feed circular polarization and high
radiation efficiency so making it suitable for implementing on
array and as well as for practical application were low losses are
salient features. Antenna have large bandwidth and circular
polarization at resonant frequency of 19.8 GHz and is suitable
for satellite to mobile high speed communication were large free
spectrum is required which is unavailable at lower frequencies.
In K-band simulated results shows 20% impedance bandwidth
and 110 MHz circular polarization band. Parametric study of
antenna’s figure of merit i.e. return loss and axial ratio with
radius of truncating circle is also illustrated.