Utpal Das - Profile on Academia.edu (original) (raw)

Papers by Utpal Das

Aerosol and Air Quality Research, 2011

The IIT Kanpur Fog Chamber Facility has been conceptualized and built indigenously to study the f... more The IIT Kanpur Fog Chamber Facility has been conceptualized and built indigenously to study the fog formation and dissipation under various environmental conditions. The chamber has been designed such that all governing parameters can be controlled and optimized. The effects of relative humidity, temperature and size distribution, number and chemical composition of fog condensation nuclei (FCN) on the formation, stability and dissipation of fog has been studied. The visibility measurements were carried out using a He-Ne 632.8 nm monochromatic laser. It was found that aerosol number concentration, size distribution and chemical nature of FCN have significant effects on visibility reduction in fog. Direct comparisons were made for theoretical droplet growth and settling times in predicting the period for which stable fog was expected Vs the actual experimentally measured times for stable fog generated using different types of FCN. Effective radius, R eff , of fog droplet size distribution (DSD), a parameter that describes the optical properties of the droplet distribution was also calculated. It was noted that even for the same R eff (i.e. similar visibility), DSDs show notable differences depending on other conditions, implying the differences in the microphysical nature of fog. Fog dissipation results show that, with the decrease in temperature, the rate of fog dissipation decreases for all FCNs except for uncoated graphite, where no particular pattern has been observed maybe due to its less hygroscopic nature. The results from this study will help us in better understanding the optical nature of fog and designing of future fog vision devices.

Inductively coupled CH4/H2 plasma etching process for mesa delineation ofInAs/GaSb type-II superlattice pixels

Micro & Nano Letters, 2019

An inductively coupled C H 4 / H 2 plasma etching process for delineation of InAs/GaSb type-II su... more An inductively coupled C H 4 / H 2 plasma etching process for delineation of InAs/GaSb type-II superlattice pixels is presented. An optimised C H 4 / H 2 etch recipe without alternate O 2 plasma cleaning step showed an etch rate as high as 0.11 μm/min that results in smooth vertical sidewalls for the type-II superlattice pixel arrays with 10 μm pitch size and 2.4 μm deep trenches. At 70 K, the dark current density for the mesa etched + SU-8 polymer passivated type-II superlattice photodiodes was found to be 0.11 A/cm2 at an applied reverse bias voltage of 0.2 V. The activation energy of 13 meV obtained from the Arrhenius plot and a variable area diode array technique showed that the measured dark current is mainly attributed to bulk tunnelling current. This technique of mesa delineation for the type-II superlattice pixel arrays with small pitch size is a viable option in realising next-generation infrared focal plane arrays.

Embedded ring resonator in InGaAsP multi-quantum wells

13th International Conference on Fiber Optics and Photonics, 2016

Embedded ring (ER) is fabricated on InGaAsP/InP multi-quantum wells using electron beam lithograp... more Embedded ring (ER) is fabricated on InGaAsP/InP multi-quantum wells using electron beam lithography and methane hydrogen reactive ion etching. Experimental findings of this ER are also compared with the theoretical study.

This study investigated the relationship between the self-efficacy of basic school headteachers i... more This study investigated the relationship between the self-efficacy of basic school headteachers in Effutu municipality and their leadership effectiveness. The purpose of the study was to determine whether the selfefficacy of Basic School Heads in Effutu Municipality affects their leadership effectiveness. The quantitative method was used for the study. A population of 85 headteachers and 145 teachers were drawn from the 85 basic schools in Effutu municipality via total/whole enumeration and random sampling techniques respectively. The structured questionnaires were used to collect the data. The quantitative survey data was analysed with SPSS, specifically, frequencies and correlation. One research question and two hypotheses were formulated to guide the study. The major finding of the study was that the basic school headteachers self-efficacy affects their leadership effectiveness and that there is a positive relationship between self-efficacy and leadership effectiveness. G.E.S. should consider the self-efficacy of teachers before selecting them as heads for Basic Schools for effective academic performance or should invest in stimulating the self-efficacy of heads so as to work effectively. Other organizations should consider building the self-efficacy of their leadership so as to improve their effectiveness in performing their duties and also, rate selfefficacy high on recruitment requirements of applicants at recruitment interviews.

Calculation of reflection efficiency in waveguide DBR by spatially selective disordering of GaAs/sub 0.19/P/sub 0.9/-Al/sub 0.3/Ga/sub 0.7/As MQWs

Conference Proceedings. LEOS'98. 11th Annual Meeting. IEEE Lasers and Electro-Optics Society 1998 Annual Meeting (Cat. No.98CH36243)

A model for refractive index change of F induced disordering of GaAsP-AlGaAs QWs shows that index... more A model for refractive index change of F induced disordering of GaAsP-AlGaAs QWs shows that index changes ~0.1-0.4 at 45 mins anneal provides 99% reflection efficiency of 500 μm long waveguide DBR

1. Enhanced persistence of fog under illumination for carbon nanotube fog condensation nuclei S. Banerjee, S. N. Tripathi, U. Das, R. Ranjan, N. Jadhav, V. P. Singh, C. Jariwala, S. K. Sonkar and S. Sarkar, J. Appl. Phys., (2012), 112, 024901

Journal of Applied Physics

Pixel isolation in Type-II InAs/GaSb superlattice photodiodes by femto-second laser annealing

SPIE Proceedings, 2015

A 775 nm femto-second laser annealed approach for the inter-pixel isolation, without mesa etching... more A 775 nm femto-second laser annealed approach for the inter-pixel isolation, without mesa etching, to reduce dark currents of type-II InAs/GaSb superlattice photodiodes is presented. A greater than two fold improvement of the pixel isolation and a corresponding reduction in the dark current are observed for laser annealed superlattice photodiodes with a 5.5 μm cutoff wavelength, operating at 10K. A higher band gap barrier material from the superlattice structure in the inter-pixel region is expected to form after femto-second laser annealing, which has been explained on the basis of a superlattice inter-diffusion model. The increase in inter-pixel barrier height at 10K is estimated to be ~ 4 meV in the laser annealed superlattice photodiodes.

Chemical beam epitaxial growth of InP, InGaP, and InAs heterojunctions using triethylindium and bisphosphinoethane

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1993

Abstract The first chemical beam epitaxial growth of InP, InGaP/InP strained layer superlattices ... more Abstract The first chemical beam epitaxial growth of InP, InGaP/InP strained layer superlattices (SLS) and InGaP/InAs/InGaP quantum wells using bisphosphinoethane and tertiarybutylarsine as group V sources is reported. Mirrorlike surface morphology and ...

High-quality materials and heterostructures on (111)B GaAs

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1992

... and heterostructures on (111)B GaAs Albert Chin and Paul Martin General Electric Electronics ... more ... and heterostructures on (111)B GaAs Albert Chin and Paul Martin General Electric Electronics Laboratory, Syracuse, New York 13221 U. Das University of Florida ... Modulation-doped heterostructures show a 77-K mobility of 145 500 cmVV s with a sheet density of 5.0x10й cm~ ...

InGaAsP/InP QW impurity free intermixing for variable ZrO2 cap thickness

IEEE Photonics Technology Letters, 2015

Impurity Free Quantum Well Intermixing (IFQWI) by cap layer thickness variation for InGaAsP/InP m... more Impurity Free Quantum Well Intermixing (IFQWI) by cap layer thickness variation for InGaAsP/InP multiquantum wells (MQWs) is reported for the first time. The blue-shift is observed to be enhanced or inhibited depending on the thickness of the ZrO2 cap layer used (100-600nm) for anneal conditions of 600-750°C for 40s. The group-V intermixing in InGaAsP/InP dominates the IFQWI resulting in a blue-shift of the MQW band gap and the blue-shift increases with increasing ZrO2 thickness to 400nm. A 600nm ZrO2 cap is found to inhibit the blue-shift. For higher anneal temperatures similar inhibition nature is observed, with larger blue-shifts. An inter-diffusion model shows that the diffusion length ratio for Group-V to Group-III initially increases from 1.25-1.6 for 100-400nm ZrO2 thickness, but decreases to 1.1 for 600nm ZrO2. This technique is promising for the fabrication of tapered waveguides for photonic integration of InGaAsP/InP by IFQWI.

Solid-State Electronics, 1986

Due to the absence of lattice-matching requirements, strained-layer superlattices offer a large t... more Due to the absence of lattice-matching requirements, strained-layer superlattices offer a large tunability in bandgap and other material properties suitable for device applications. Encouraging progress has been made in the molecular-beam epitaxial and metalorganic-vapor-phase-epitaxial growth of strained-layer superlattices and in their characterization. These have been briefly reviewed here. Since a strained-layer superlattice allows the use of InzGa,_,vAs layers with x-values up to-1.0, a large variation of the refractive index from that in GaAs occurs due to mismatch strain and alloying. This variation in refractive index has been calculated. The increase in refractive index can be used to form optical guides in the SLS and such guides with good vertical confinement is demonstrated. Preliminary measurements of the impact-ionization parameters and deep-level traps in these materials are also reported. a/@ values close to and slightly greater than unity are measured. A single electron trap with thermal activation energy equal to 0.16 eV is identified.

SiC light emitting quantized structures on silicon by spin-on technique

16th International Workshop on Physics of Semiconductor Devices, 2012

ABSTRACT SiC nanocrystals of size 4×30×40nm have been fabricated on Si (100)3° by a low cost spin... more ABSTRACT SiC nanocrystals of size 4×30×40nm have been fabricated on Si (100)3° by a low cost spin-on technique in which Htermination produces smaller crystallites but larger crystallite density at the substrate surface steps. Low temperature photoluminescence and atomic force microscopy (AFM) confirms the formation of quantum dashes. It has been observed that the spin speed and H-termination plays a crucial role in the formation of quantized structures on Si.

Integrated Waveguide Grating Using Impurity Induced Quantum Well Intermixing

Asia Optical Fiber Communication and Optoelectronic Exposition and Conference, 2008

Abstract This paper presents the work on InGaAsP/InP multi quantum well impurity intermixed waveg... more Abstract This paper presents the work on InGaAsP/InP multi quantum well impurity intermixed waveguide grating suitable for CWDM wavelength range. A channel bandwidth of 13nm and cross-talk in between-5dB to-10dB is obtained.

CWDM integrated waveguide gratings by InGaAsP/InP quantum well intermixing

2012 7th International Conference on Electrical and Computer Engineering, 2012

ABSTRACT Integrated waveguide Bragg gratings have been designed and fabricated for CWDM wavelengt... more ABSTRACT Integrated waveguide Bragg gratings have been designed and fabricated for CWDM wavelengths using F implantation and annealed quantum well intermixing technique, compatible with microelectronics processing. The measured peaks are blue shifted by ~35nm from that of the design and FWHM width widened by ~1nm due to inaccuracies in the processing. The measured insertion loss is ~4dB.

Fabrication of F-ion implanted quantum well intermixed waveguide grating

2012 Photonics Global Conference (PGC), 2012

ABSTRACT This paper reports the ion implantation induced quantum well intermixing used to fabrica... more ABSTRACT This paper reports the ion implantation induced quantum well intermixing used to fabricate waveguide gratings for applications at CWDM wavelengths on InGaAsP/InP multi quantum well structure. The waveguide is fabricated using reactive ion etching (methane chemistry) with a surface roughness 2~3nm. Focused ion beam is used to open windows for fluorine implantation on titanium mask followed by anneal under forming gas environment. The transmission spectrum of the waveguide has been measured and found cross talks of -10dB among the adjacent channels. The insertion loss of the fabricated waveguide gratings is less than 5dB.

Analysis of implantation induced gratings for CWDM

2005 Quantum Electronics and Laser Science Conference

Abstract The Bragg reflection coefficients suitable for a CWDM system have been calculated by usi... more Abstract The Bragg reflection coefficients suitable for a CWDM system have been calculated by using coupled mode theory based on perturbation obtained by impurity induced intermixing of quantum wells and analyzed for different order gratings.

40GHz integrated multi quantum well intermixed waveguide photodiodes

16th International Workshop on Physics of Semiconductor Devices, 2012

InGaAsP/InP Multi Quantum Well (MQW) based rib waveguide (WG) multi-wavelength PIN type photodiod... more InGaAsP/InP Multi Quantum Well (MQW) based rib waveguide (WG) multi-wavelength PIN type photodiodes (PD) have been designed for Coarse Wavelength Division Multiplexing (CWDM) systems in which spatial bandgap tailoring have been accomplished by using post growth Fluorine (F) implanted QW Intermixing (QWI) as the integration mechanism. Two separate structures with different composition but same well widths are necessary to detect all CWDM wavelengths in which a In0.5540Ga0.4460As0.9489P0.0511/InP (15nm/15nm) MQW structure has a 14 channel coverage which spans from 1350-1610nm. The thicknesses of the i-MQW layer and different layers constituting the WG have been optimized to give a maximum efficiency of 22%. A carrier tunneling time of 20ps along with the transit time limited bandwidth of 86GHz gives a 3dB bandwidth of 43GHz by optimizing the i-MQW thickness and dopant concentration of the different layers of the waveguide. For all 18 channels insertion loss of 0.4-23dB has been obtained for a detection sensitivity of 21dB. Design issues related to the contact formation for extracting the photo-generated microwave power in such photodiodes have been presented along with few fabrication details of the integration process.

Optics Letters, 1987

A monolithically integrated guided-wave modulator has been realized by using molecular-beam epita... more A monolithically integrated guided-wave modulator has been realized by using molecular-beam epitaxial regrowth and ion-milling techniques. The guiding and modulating regions consist, respectively, of In-doped GaAs and GaAs/InO. 34 GaO. 6 6As strained-layer multiquantum wells. Modulation is achieved by field-enhanced electroabsorption in the multiquantum wells. The insertion loss of the modulator is 0.9 dB, and the transmission loss in the guides is <1 dB/cm. The temporal response of similar GaAs/InGaAs as-grown photodiodes to pulsed laser excitation is characterized by a rise time of 115 psec.

Optical and Quantum Electronics, 2010

A multi-wavelength Quantum well (QW) waveguide photodiode (PD) have been designed for Coarse Wave... more A multi-wavelength Quantum well (QW) waveguide photodiode (PD) have been designed for Coarse Wavelength Division Multiplexing (CWDM) systems in which spatial tailoring of the bandgap with post growth F implanted QW intermixing of InGaAsP/InP multi QWs for the integration have been considered. Two separate structures with different composition but same well widths are necessary to detect all CWDM wavelengths. For In 0.5995 Ga 0.4005 As 0.8521 P 0.1479 well there is a 12 channel coverage from 1,270 to 1,490 nm and for the In 0.5540 Ga 0.4460 As 0.9489 P 0.0511 well the 14 channel spans from 1,350 to 1,610 nm. A carrier tunneling time of 20 ps along with the transit time limited bandwidth of 86 GHz gives a 3 dB bandwidth of 41 GHz by optimizing the i-MQW thickness and dopant concentration of the different layers of the waveguide. A maximum efficiency of 22% with insertion loss of 0.4-23 dB has been obtained.

Suspended substrate bias-T at 2.5-10 GHz

Microwave and Optical Technology Letters, 2000

An analysis of a radial suspended substrate (SS) stub-connected bias-T with the variational techn... more An analysis of a radial suspended substrate (SS) stub-connected bias-T with the variational technique and cascade network theory is presented incorporating end effects and losses. Calculated frequency-dependent stub impedances match well with published values from other ...

Aerosol and Air Quality Research, 2011

The IIT Kanpur Fog Chamber Facility has been conceptualized and built indigenously to study the f... more The IIT Kanpur Fog Chamber Facility has been conceptualized and built indigenously to study the fog formation and dissipation under various environmental conditions. The chamber has been designed such that all governing parameters can be controlled and optimized. The effects of relative humidity, temperature and size distribution, number and chemical composition of fog condensation nuclei (FCN) on the formation, stability and dissipation of fog has been studied. The visibility measurements were carried out using a He-Ne 632.8 nm monochromatic laser. It was found that aerosol number concentration, size distribution and chemical nature of FCN have significant effects on visibility reduction in fog. Direct comparisons were made for theoretical droplet growth and settling times in predicting the period for which stable fog was expected Vs the actual experimentally measured times for stable fog generated using different types of FCN. Effective radius, R eff , of fog droplet size distribution (DSD), a parameter that describes the optical properties of the droplet distribution was also calculated. It was noted that even for the same R eff (i.e. similar visibility), DSDs show notable differences depending on other conditions, implying the differences in the microphysical nature of fog. Fog dissipation results show that, with the decrease in temperature, the rate of fog dissipation decreases for all FCNs except for uncoated graphite, where no particular pattern has been observed maybe due to its less hygroscopic nature. The results from this study will help us in better understanding the optical nature of fog and designing of future fog vision devices.

Inductively coupled CH4/H2 plasma etching process for mesa delineation ofInAs/GaSb type-II superlattice pixels

Micro & Nano Letters, 2019

An inductively coupled C H 4 / H 2 plasma etching process for delineation of InAs/GaSb type-II su... more An inductively coupled C H 4 / H 2 plasma etching process for delineation of InAs/GaSb type-II superlattice pixels is presented. An optimised C H 4 / H 2 etch recipe without alternate O 2 plasma cleaning step showed an etch rate as high as 0.11 μm/min that results in smooth vertical sidewalls for the type-II superlattice pixel arrays with 10 μm pitch size and 2.4 μm deep trenches. At 70 K, the dark current density for the mesa etched + SU-8 polymer passivated type-II superlattice photodiodes was found to be 0.11 A/cm2 at an applied reverse bias voltage of 0.2 V. The activation energy of 13 meV obtained from the Arrhenius plot and a variable area diode array technique showed that the measured dark current is mainly attributed to bulk tunnelling current. This technique of mesa delineation for the type-II superlattice pixel arrays with small pitch size is a viable option in realising next-generation infrared focal plane arrays.

Embedded ring resonator in InGaAsP multi-quantum wells

13th International Conference on Fiber Optics and Photonics, 2016

Embedded ring (ER) is fabricated on InGaAsP/InP multi-quantum wells using electron beam lithograp... more Embedded ring (ER) is fabricated on InGaAsP/InP multi-quantum wells using electron beam lithography and methane hydrogen reactive ion etching. Experimental findings of this ER are also compared with the theoretical study.

This study investigated the relationship between the self-efficacy of basic school headteachers i... more This study investigated the relationship between the self-efficacy of basic school headteachers in Effutu municipality and their leadership effectiveness. The purpose of the study was to determine whether the selfefficacy of Basic School Heads in Effutu Municipality affects their leadership effectiveness. The quantitative method was used for the study. A population of 85 headteachers and 145 teachers were drawn from the 85 basic schools in Effutu municipality via total/whole enumeration and random sampling techniques respectively. The structured questionnaires were used to collect the data. The quantitative survey data was analysed with SPSS, specifically, frequencies and correlation. One research question and two hypotheses were formulated to guide the study. The major finding of the study was that the basic school headteachers self-efficacy affects their leadership effectiveness and that there is a positive relationship between self-efficacy and leadership effectiveness. G.E.S. should consider the self-efficacy of teachers before selecting them as heads for Basic Schools for effective academic performance or should invest in stimulating the self-efficacy of heads so as to work effectively. Other organizations should consider building the self-efficacy of their leadership so as to improve their effectiveness in performing their duties and also, rate selfefficacy high on recruitment requirements of applicants at recruitment interviews.

Calculation of reflection efficiency in waveguide DBR by spatially selective disordering of GaAs/sub 0.19/P/sub 0.9/-Al/sub 0.3/Ga/sub 0.7/As MQWs

Conference Proceedings. LEOS'98. 11th Annual Meeting. IEEE Lasers and Electro-Optics Society 1998 Annual Meeting (Cat. No.98CH36243)

A model for refractive index change of F induced disordering of GaAsP-AlGaAs QWs shows that index... more A model for refractive index change of F induced disordering of GaAsP-AlGaAs QWs shows that index changes ~0.1-0.4 at 45 mins anneal provides 99% reflection efficiency of 500 μm long waveguide DBR

1. Enhanced persistence of fog under illumination for carbon nanotube fog condensation nuclei S. Banerjee, S. N. Tripathi, U. Das, R. Ranjan, N. Jadhav, V. P. Singh, C. Jariwala, S. K. Sonkar and S. Sarkar, J. Appl. Phys., (2012), 112, 024901

Journal of Applied Physics

Pixel isolation in Type-II InAs/GaSb superlattice photodiodes by femto-second laser annealing

SPIE Proceedings, 2015

A 775 nm femto-second laser annealed approach for the inter-pixel isolation, without mesa etching... more A 775 nm femto-second laser annealed approach for the inter-pixel isolation, without mesa etching, to reduce dark currents of type-II InAs/GaSb superlattice photodiodes is presented. A greater than two fold improvement of the pixel isolation and a corresponding reduction in the dark current are observed for laser annealed superlattice photodiodes with a 5.5 μm cutoff wavelength, operating at 10K. A higher band gap barrier material from the superlattice structure in the inter-pixel region is expected to form after femto-second laser annealing, which has been explained on the basis of a superlattice inter-diffusion model. The increase in inter-pixel barrier height at 10K is estimated to be ~ 4 meV in the laser annealed superlattice photodiodes.

Chemical beam epitaxial growth of InP, InGaP, and InAs heterojunctions using triethylindium and bisphosphinoethane

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1993

Abstract The first chemical beam epitaxial growth of InP, InGaP/InP strained layer superlattices ... more Abstract The first chemical beam epitaxial growth of InP, InGaP/InP strained layer superlattices (SLS) and InGaP/InAs/InGaP quantum wells using bisphosphinoethane and tertiarybutylarsine as group V sources is reported. Mirrorlike surface morphology and ...

High-quality materials and heterostructures on (111)B GaAs

Journal of Vacuum Science & Technology B: Microelectronics and Nanometer Structures, 1992

... and heterostructures on (111)B GaAs Albert Chin and Paul Martin General Electric Electronics ... more ... and heterostructures on (111)B GaAs Albert Chin and Paul Martin General Electric Electronics Laboratory, Syracuse, New York 13221 U. Das University of Florida ... Modulation-doped heterostructures show a 77-K mobility of 145 500 cmVV s with a sheet density of 5.0x10й cm~ ...

InGaAsP/InP QW impurity free intermixing for variable ZrO2 cap thickness

IEEE Photonics Technology Letters, 2015

Impurity Free Quantum Well Intermixing (IFQWI) by cap layer thickness variation for InGaAsP/InP m... more Impurity Free Quantum Well Intermixing (IFQWI) by cap layer thickness variation for InGaAsP/InP multiquantum wells (MQWs) is reported for the first time. The blue-shift is observed to be enhanced or inhibited depending on the thickness of the ZrO2 cap layer used (100-600nm) for anneal conditions of 600-750°C for 40s. The group-V intermixing in InGaAsP/InP dominates the IFQWI resulting in a blue-shift of the MQW band gap and the blue-shift increases with increasing ZrO2 thickness to 400nm. A 600nm ZrO2 cap is found to inhibit the blue-shift. For higher anneal temperatures similar inhibition nature is observed, with larger blue-shifts. An inter-diffusion model shows that the diffusion length ratio for Group-V to Group-III initially increases from 1.25-1.6 for 100-400nm ZrO2 thickness, but decreases to 1.1 for 600nm ZrO2. This technique is promising for the fabrication of tapered waveguides for photonic integration of InGaAsP/InP by IFQWI.

Solid-State Electronics, 1986

Due to the absence of lattice-matching requirements, strained-layer superlattices offer a large t... more Due to the absence of lattice-matching requirements, strained-layer superlattices offer a large tunability in bandgap and other material properties suitable for device applications. Encouraging progress has been made in the molecular-beam epitaxial and metalorganic-vapor-phase-epitaxial growth of strained-layer superlattices and in their characterization. These have been briefly reviewed here. Since a strained-layer superlattice allows the use of InzGa,_,vAs layers with x-values up to-1.0, a large variation of the refractive index from that in GaAs occurs due to mismatch strain and alloying. This variation in refractive index has been calculated. The increase in refractive index can be used to form optical guides in the SLS and such guides with good vertical confinement is demonstrated. Preliminary measurements of the impact-ionization parameters and deep-level traps in these materials are also reported. a/@ values close to and slightly greater than unity are measured. A single electron trap with thermal activation energy equal to 0.16 eV is identified.

SiC light emitting quantized structures on silicon by spin-on technique

16th International Workshop on Physics of Semiconductor Devices, 2012

ABSTRACT SiC nanocrystals of size 4×30×40nm have been fabricated on Si (100)3° by a low cost spin... more ABSTRACT SiC nanocrystals of size 4×30×40nm have been fabricated on Si (100)3° by a low cost spin-on technique in which Htermination produces smaller crystallites but larger crystallite density at the substrate surface steps. Low temperature photoluminescence and atomic force microscopy (AFM) confirms the formation of quantum dashes. It has been observed that the spin speed and H-termination plays a crucial role in the formation of quantized structures on Si.

Integrated Waveguide Grating Using Impurity Induced Quantum Well Intermixing

Asia Optical Fiber Communication and Optoelectronic Exposition and Conference, 2008

Abstract This paper presents the work on InGaAsP/InP multi quantum well impurity intermixed waveg... more Abstract This paper presents the work on InGaAsP/InP multi quantum well impurity intermixed waveguide grating suitable for CWDM wavelength range. A channel bandwidth of 13nm and cross-talk in between-5dB to-10dB is obtained.

CWDM integrated waveguide gratings by InGaAsP/InP quantum well intermixing

2012 7th International Conference on Electrical and Computer Engineering, 2012

ABSTRACT Integrated waveguide Bragg gratings have been designed and fabricated for CWDM wavelengt... more ABSTRACT Integrated waveguide Bragg gratings have been designed and fabricated for CWDM wavelengths using F implantation and annealed quantum well intermixing technique, compatible with microelectronics processing. The measured peaks are blue shifted by ~35nm from that of the design and FWHM width widened by ~1nm due to inaccuracies in the processing. The measured insertion loss is ~4dB.

Fabrication of F-ion implanted quantum well intermixed waveguide grating

2012 Photonics Global Conference (PGC), 2012

ABSTRACT This paper reports the ion implantation induced quantum well intermixing used to fabrica... more ABSTRACT This paper reports the ion implantation induced quantum well intermixing used to fabricate waveguide gratings for applications at CWDM wavelengths on InGaAsP/InP multi quantum well structure. The waveguide is fabricated using reactive ion etching (methane chemistry) with a surface roughness 2~3nm. Focused ion beam is used to open windows for fluorine implantation on titanium mask followed by anneal under forming gas environment. The transmission spectrum of the waveguide has been measured and found cross talks of -10dB among the adjacent channels. The insertion loss of the fabricated waveguide gratings is less than 5dB.

Analysis of implantation induced gratings for CWDM

2005 Quantum Electronics and Laser Science Conference

Abstract The Bragg reflection coefficients suitable for a CWDM system have been calculated by usi... more Abstract The Bragg reflection coefficients suitable for a CWDM system have been calculated by using coupled mode theory based on perturbation obtained by impurity induced intermixing of quantum wells and analyzed for different order gratings.

40GHz integrated multi quantum well intermixed waveguide photodiodes

16th International Workshop on Physics of Semiconductor Devices, 2012

InGaAsP/InP Multi Quantum Well (MQW) based rib waveguide (WG) multi-wavelength PIN type photodiod... more InGaAsP/InP Multi Quantum Well (MQW) based rib waveguide (WG) multi-wavelength PIN type photodiodes (PD) have been designed for Coarse Wavelength Division Multiplexing (CWDM) systems in which spatial bandgap tailoring have been accomplished by using post growth Fluorine (F) implanted QW Intermixing (QWI) as the integration mechanism. Two separate structures with different composition but same well widths are necessary to detect all CWDM wavelengths in which a In0.5540Ga0.4460As0.9489P0.0511/InP (15nm/15nm) MQW structure has a 14 channel coverage which spans from 1350-1610nm. The thicknesses of the i-MQW layer and different layers constituting the WG have been optimized to give a maximum efficiency of 22%. A carrier tunneling time of 20ps along with the transit time limited bandwidth of 86GHz gives a 3dB bandwidth of 43GHz by optimizing the i-MQW thickness and dopant concentration of the different layers of the waveguide. For all 18 channels insertion loss of 0.4-23dB has been obtained for a detection sensitivity of 21dB. Design issues related to the contact formation for extracting the photo-generated microwave power in such photodiodes have been presented along with few fabrication details of the integration process.

Optics Letters, 1987

A monolithically integrated guided-wave modulator has been realized by using molecular-beam epita... more A monolithically integrated guided-wave modulator has been realized by using molecular-beam epitaxial regrowth and ion-milling techniques. The guiding and modulating regions consist, respectively, of In-doped GaAs and GaAs/InO. 34 GaO. 6 6As strained-layer multiquantum wells. Modulation is achieved by field-enhanced electroabsorption in the multiquantum wells. The insertion loss of the modulator is 0.9 dB, and the transmission loss in the guides is <1 dB/cm. The temporal response of similar GaAs/InGaAs as-grown photodiodes to pulsed laser excitation is characterized by a rise time of 115 psec.

Optical and Quantum Electronics, 2010

A multi-wavelength Quantum well (QW) waveguide photodiode (PD) have been designed for Coarse Wave... more A multi-wavelength Quantum well (QW) waveguide photodiode (PD) have been designed for Coarse Wavelength Division Multiplexing (CWDM) systems in which spatial tailoring of the bandgap with post growth F implanted QW intermixing of InGaAsP/InP multi QWs for the integration have been considered. Two separate structures with different composition but same well widths are necessary to detect all CWDM wavelengths. For In 0.5995 Ga 0.4005 As 0.8521 P 0.1479 well there is a 12 channel coverage from 1,270 to 1,490 nm and for the In 0.5540 Ga 0.4460 As 0.9489 P 0.0511 well the 14 channel spans from 1,350 to 1,610 nm. A carrier tunneling time of 20 ps along with the transit time limited bandwidth of 86 GHz gives a 3 dB bandwidth of 41 GHz by optimizing the i-MQW thickness and dopant concentration of the different layers of the waveguide. A maximum efficiency of 22% with insertion loss of 0.4-23 dB has been obtained.

Suspended substrate bias-T at 2.5-10 GHz

Microwave and Optical Technology Letters, 2000

An analysis of a radial suspended substrate (SS) stub-connected bias-T with the variational techn... more An analysis of a radial suspended substrate (SS) stub-connected bias-T with the variational technique and cascade network theory is presented incorporating end effects and losses. Calculated frequency-dependent stub impedances match well with published values from other ...