Sangam Chatterjee - Academia.edu (original) (raw)
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Papers by Sangam Chatterjee
2007 Quantum Electronics and Laser Science Conference, 2007
ABSTRACT We report on the lasing dynamics of semiconductor disk lasers following well and barrier... more ABSTRACT We report on the lasing dynamics of semiconductor disk lasers following well and barrier pumping with both 500ns and 5 ¿s pulses. The dynamics are explained using rate-equations.
2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, 2007
We report on the lasing and photoluminescence dynamics of 1050nm semiconductor disk lasers using ... more We report on the lasing and photoluminescence dynamics of 1050nm semiconductor disk lasers using well and barrier pumping. Spectral and temporal features are explained using a rate equation model including microscopic gain and luminescence.
2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, 2007
In recent years, vertical cavity surface emitting lasers (VCSEL) have developed into an important... more In recent years, vertical cavity surface emitting lasers (VCSEL) have developed into an important semiconductor laser source in multiple applications. However, the limited output power of VCSEL systems restrains industrial applications. The vertical external cavity surface emitting laser (VECSEL) design overcomes this limitation by replacing the upper distributed bragg reflector by an external parabolic mirror. Nevertheless, heating of the active
Advances in Solid State Physics, 2009
This article reviews our THz-spectroscopy results on the intra-excitonic transitions of different... more This article reviews our THz-spectroscopy results on the intra-excitonic transitions of different III–V multi quantum well structures. Following a brief introduction to THz Time-Domain Spectroscopy a detailed description to the data analysis and extraction of refractive index and absorption is given. The behavior of the induced excitonic THz absorption in GaAs/(AlGa)As and (GaIn)As/GaAs multi quantum well structures is compared. Good
Physical Review B, 2001
ABSTRACT
2009 6th IEEE International Conference on Group IV Photonics, 2009
Ga(NAsP) multi quantum well heterostructures were grown pseudomorphically on exactly oriented (00... more Ga(NAsP) multi quantum well heterostructures were grown pseudomorphically on exactly oriented (001) silicon substrates without the formation of misfit dislocations. Optical pumped lasing operation was observed at temperatures up to 125 K.
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009
A finite density-dependent plasmon pole is observed in the inverse dielectric response function o... more A finite density-dependent plasmon pole is observed in the inverse dielectric response function of a two-dimensional electron gas by THz-spectroscopy. A microscopic many-body theory explains the experimental results.
2008 Device Research Conference, 2008
The focus of the present study is the optical characterisation of the novel direct band gap mater... more The focus of the present study is the optical characterisation of the novel direct band gap material Ga(NAsP) monolithically grown on Si substrate. Ga(NAsP)/(BGa)(AsP) multi-quantum-well heterostructures (MQWHs) were deposited by low temperature metal organic vapour phase epitaxy (MOVPE) in a commercial reactor system on nominally exact (001) Si substrates. In order to realise III/V laser diode the MQWH layer-stack was
2009 Device Research Conference, 2009
Nowadays silicon photonics gains more and more interest especially for the future architecture of... more Nowadays silicon photonics gains more and more interest especially for the future architecture of Si based optoelectronic integrated circuits (OEI C). OEIC building blocks such a s modulators, detectors as well as light wave guides have been demonstrated in a down-scalable process technology. However, a commercial solution for the monolithic integration of long-term stable laser diodes has not been achieved
35th International Conference on Infrared, Millimeter, and Terahertz Waves, 2010
ABSTRACT Understanding the interactions of the crystalline and the amorphous domains in semi-crys... more ABSTRACT Understanding the interactions of the crystalline and the amorphous domains in semi-crystalline polymers, such as HDPE or PVDF, is a subject of ongoing research. Here, we apply terahertz time-domain spectroscopy to study the impact of the glass transition taking place in the amorphous phase on lattice modes associated with the crystalline domains.
Optics letters, Jan 15, 2014
We present a fast and low-cost delay generator for terahertz (THz) waves that transfers a rotatio... more We present a fast and low-cost delay generator for terahertz (THz) waves that transfers a rotational motion of a transparent dielectric cube into an effective THz delay. The device is easily implemented in the THz beam path and allows for coherent sampling over 40 ps with a scan rate of hundreds of hertz. Furthermore, we show that our approach is particularly suitable for fast THz imaging.
Optics express, Jan 15, 2010
Spatially resolved photocurrent-spectroscopy and spatially resolved current-voltage characteristi... more Spatially resolved photocurrent-spectroscopy and spatially resolved current-voltage characteristics are introduced as new methods to characterize solar cells. A combination of these two methods is shown to localize and characterize deficiencies and structural damages in processed solar cells with high spatial resolution. The local external and internal quantum efficiencies as well as the local characteristic parameters of the p-n junction like the short circuit current, the saturation current, the ideality factor, and the optically induced shunt resistance can be determined quantitatively. Both, a slab of a damaged and an undamaged (GaIn)(NAs) concentrator solar cell, are used as test structures. Upon these test structures domains with a high concentration of impurities in the crystal structure and structural imperfections in the upper contact region are identified and analyzed. Additional numerical simulations prove the reliability and show limits of the methods.
ABSTRACT The carrier dynamics that occurs in Ge/SiGe QWs when electrons are excited to confined s... more ABSTRACT The carrier dynamics that occurs in Ge/SiGe QWs when electrons are excited to confined states at Γ is studied by means of optical spectroscopy at different lattice temperatures. The typical times for the different relaxation nd recombination processes are given and discussed.
2009 6th IEEE International Conference on Group IV Photonics, 2009
Ultrafast carrier dynamics of Ge/SiGe quantum wells grown on a Si substrate are investigated usin... more Ultrafast carrier dynamics of Ge/SiGe quantum wells grown on a Si substrate are investigated using pump-probe spectroscopy. Optical gain and population inversion are obtained on a femtosecond time scale. A microscopic theory supports the results.
Conference on Lasers and Electro-Optics 2012, 2012
Conference on Lasers and Electro-Optics 2012, 2012
A systematic study of carrier relaxation in Ge quantum wells is performed applying photoluminesce... more A systematic study of carrier relaxation in Ge quantum wells is performed applying photoluminescence and pump-probe spectroscopy. Intersubband-relaxation on a 100 fs time-scale and the presence of a non-thermal carrier distribution are identified.
ECS Transactions, 2013
ABSTRACT Ge is emerging as an interesting material for spintronic applications. We demonstrate th... more ABSTRACT Ge is emerging as an interesting material for spintronic applications. We demonstrate that in SiGe heterostructures strain and quantum confinement effects can be used to tailor spin related properties enhancing the spin polarization of injected carriers above the bulk limit. Moreover the fast Γ-L electron scattering and the strain induced removal of the heavy-hole, light-hole degeneracy, make SiGe heterostructures an ideal material platform for the study of hole dynamics.
2007 Quantum Electronics and Laser Science Conference, 2007
ABSTRACT We report on the lasing dynamics of semiconductor disk lasers following well and barrier... more ABSTRACT We report on the lasing dynamics of semiconductor disk lasers following well and barrier pumping with both 500ns and 5 ¿s pulses. The dynamics are explained using rate-equations.
2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, 2007
We report on the lasing and photoluminescence dynamics of 1050nm semiconductor disk lasers using ... more We report on the lasing and photoluminescence dynamics of 1050nm semiconductor disk lasers using well and barrier pumping. Spectral and temporal features are explained using a rate equation model including microscopic gain and luminescence.
2007 European Conference on Lasers and Electro-Optics and the International Quantum Electronics Conference, 2007
In recent years, vertical cavity surface emitting lasers (VCSEL) have developed into an important... more In recent years, vertical cavity surface emitting lasers (VCSEL) have developed into an important semiconductor laser source in multiple applications. However, the limited output power of VCSEL systems restrains industrial applications. The vertical external cavity surface emitting laser (VECSEL) design overcomes this limitation by replacing the upper distributed bragg reflector by an external parabolic mirror. Nevertheless, heating of the active
Advances in Solid State Physics, 2009
This article reviews our THz-spectroscopy results on the intra-excitonic transitions of different... more This article reviews our THz-spectroscopy results on the intra-excitonic transitions of different III–V multi quantum well structures. Following a brief introduction to THz Time-Domain Spectroscopy a detailed description to the data analysis and extraction of refractive index and absorption is given. The behavior of the induced excitonic THz absorption in GaAs/(AlGa)As and (GaIn)As/GaAs multi quantum well structures is compared. Good
Physical Review B, 2001
ABSTRACT
2009 6th IEEE International Conference on Group IV Photonics, 2009
Ga(NAsP) multi quantum well heterostructures were grown pseudomorphically on exactly oriented (00... more Ga(NAsP) multi quantum well heterostructures were grown pseudomorphically on exactly oriented (001) silicon substrates without the formation of misfit dislocations. Optical pumped lasing operation was observed at temperatures up to 125 K.
Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, 2009
A finite density-dependent plasmon pole is observed in the inverse dielectric response function o... more A finite density-dependent plasmon pole is observed in the inverse dielectric response function of a two-dimensional electron gas by THz-spectroscopy. A microscopic many-body theory explains the experimental results.
2008 Device Research Conference, 2008
The focus of the present study is the optical characterisation of the novel direct band gap mater... more The focus of the present study is the optical characterisation of the novel direct band gap material Ga(NAsP) monolithically grown on Si substrate. Ga(NAsP)/(BGa)(AsP) multi-quantum-well heterostructures (MQWHs) were deposited by low temperature metal organic vapour phase epitaxy (MOVPE) in a commercial reactor system on nominally exact (001) Si substrates. In order to realise III/V laser diode the MQWH layer-stack was
2009 Device Research Conference, 2009
Nowadays silicon photonics gains more and more interest especially for the future architecture of... more Nowadays silicon photonics gains more and more interest especially for the future architecture of Si based optoelectronic integrated circuits (OEI C). OEIC building blocks such a s modulators, detectors as well as light wave guides have been demonstrated in a down-scalable process technology. However, a commercial solution for the monolithic integration of long-term stable laser diodes has not been achieved
35th International Conference on Infrared, Millimeter, and Terahertz Waves, 2010
ABSTRACT Understanding the interactions of the crystalline and the amorphous domains in semi-crys... more ABSTRACT Understanding the interactions of the crystalline and the amorphous domains in semi-crystalline polymers, such as HDPE or PVDF, is a subject of ongoing research. Here, we apply terahertz time-domain spectroscopy to study the impact of the glass transition taking place in the amorphous phase on lattice modes associated with the crystalline domains.
Optics letters, Jan 15, 2014
We present a fast and low-cost delay generator for terahertz (THz) waves that transfers a rotatio... more We present a fast and low-cost delay generator for terahertz (THz) waves that transfers a rotational motion of a transparent dielectric cube into an effective THz delay. The device is easily implemented in the THz beam path and allows for coherent sampling over 40 ps with a scan rate of hundreds of hertz. Furthermore, we show that our approach is particularly suitable for fast THz imaging.
Optics express, Jan 15, 2010
Spatially resolved photocurrent-spectroscopy and spatially resolved current-voltage characteristi... more Spatially resolved photocurrent-spectroscopy and spatially resolved current-voltage characteristics are introduced as new methods to characterize solar cells. A combination of these two methods is shown to localize and characterize deficiencies and structural damages in processed solar cells with high spatial resolution. The local external and internal quantum efficiencies as well as the local characteristic parameters of the p-n junction like the short circuit current, the saturation current, the ideality factor, and the optically induced shunt resistance can be determined quantitatively. Both, a slab of a damaged and an undamaged (GaIn)(NAs) concentrator solar cell, are used as test structures. Upon these test structures domains with a high concentration of impurities in the crystal structure and structural imperfections in the upper contact region are identified and analyzed. Additional numerical simulations prove the reliability and show limits of the methods.
ABSTRACT The carrier dynamics that occurs in Ge/SiGe QWs when electrons are excited to confined s... more ABSTRACT The carrier dynamics that occurs in Ge/SiGe QWs when electrons are excited to confined states at Γ is studied by means of optical spectroscopy at different lattice temperatures. The typical times for the different relaxation nd recombination processes are given and discussed.
2009 6th IEEE International Conference on Group IV Photonics, 2009
Ultrafast carrier dynamics of Ge/SiGe quantum wells grown on a Si substrate are investigated usin... more Ultrafast carrier dynamics of Ge/SiGe quantum wells grown on a Si substrate are investigated using pump-probe spectroscopy. Optical gain and population inversion are obtained on a femtosecond time scale. A microscopic theory supports the results.
Conference on Lasers and Electro-Optics 2012, 2012
Conference on Lasers and Electro-Optics 2012, 2012
A systematic study of carrier relaxation in Ge quantum wells is performed applying photoluminesce... more A systematic study of carrier relaxation in Ge quantum wells is performed applying photoluminescence and pump-probe spectroscopy. Intersubband-relaxation on a 100 fs time-scale and the presence of a non-thermal carrier distribution are identified.
ECS Transactions, 2013
ABSTRACT Ge is emerging as an interesting material for spintronic applications. We demonstrate th... more ABSTRACT Ge is emerging as an interesting material for spintronic applications. We demonstrate that in SiGe heterostructures strain and quantum confinement effects can be used to tailor spin related properties enhancing the spin polarization of injected carriers above the bulk limit. Moreover the fast Γ-L electron scattering and the strain induced removal of the heavy-hole, light-hole degeneracy, make SiGe heterostructures an ideal material platform for the study of hole dynamics.