The link between the inversion gain of quantum cascade structures and the Bloch gain in periodic ... more The link between the inversion gain of quantum cascade structures and the Bloch gain in periodic superlattices is presented. The proposed theoretical model based on the density matrix formalism is able to treat the gain mechanism of the Bloch oscillator and Quantum cascade laser on the same footing by taking into account in-plane momentum relaxation. The model predicts a dispersive contribution in addition to the (usual) population-inversion-dependent intersubband gain in quantum cascade structures and-in the absence of inversion-provides the quantum mechanical description for the dispersive gain in superlattices. It corroborates the predictions of the semi-classical miniband picture, according to which gain is predicted for photon energies lower than the Bloch oscillation frequency, whereas net absorption is expected at higher photon energies, as a description which is valid in the high-temperature limit. A red-shift of the amplified emission with respect to the resonant transition energy results from the dispersive gain contribution in any intersubband transition, for which the population inversion is small.
Physica E: Low-dimensional Systems and Nanostructures, 2008
We report simulations and experimental results of THz QCLs with quasi-periodic resonators based o... more We report simulations and experimental results of THz QCLs with quasi-periodic resonators based on a Fibonacci sequence.
This page was generated automatically upon download from the ETH Zurich Research Collection. For ... more This page was generated automatically upon download from the ETH Zurich Research Collection. For more information please consult the Terms of use. ETH Library PAPER • OPEN ACCESS Enhanced current injection from a quantum well to a quantum dash in magnetic field To cite this article: Gian L Paravicini-Bagliani et al 2014 New J. Phys. 16 083029 View the article online for updates and enhancements. Recent citations Carrier transfer efficiency and its influence on emission properties of telecom wavelength InP-based quantum dotquantum well structures Wojciech Rudno-Rudziski et al-Carrier diffusion as a measure of carrier/exciton transfer rate in InAs/InGaAsP/InP hybrid quantum dot-quantum well structures emitting at telecom spectral range W. Rudno-Rudziski et al-Carrier delocalization in InAs/InGaAlAs/InP quantum-dash-based tunnel injection system for 1.55 µm emission W. Rudno-Rudziski et al
Pulsed single mode operation of distributed feedback quantum cascade lasers is reported above roo... more Pulsed single mode operation of distributed feedback quantum cascade lasers is reported above room temperature at both 5.4 and 8 μm wavelengths. Peak optical powers up to 60 mW at 300 K are obtained with a tuning range of ∼60 nm from 100 to ∼320 K. The linewidth is limited by thermal drift during the pulse with a typical value of 0.3 cm−1 for a 10 ns long pulse at 300 K.
We report on the development of nanowire-based field-effect transistors operating as high sensiti... more We report on the development of nanowire-based field-effect transistors operating as high sensitivity terahertz (THz) detectors. By feeding the 1.5 THz radiation field of a quantum cascade laser (QCL) at the gate-source electrodes with a wide band dipole antenna, we record a photovoltage signal corresponding to responsivity values >10 V/W, with impressive noise equivalent power levels <6 × 10−11 W/√Hz at room temperature and a wide modulation bandwidth. The potential scalability to even higher frequencies and the technological feasibility of realizing multi-pixel arrays coupled with QCL sources make the proposed technology highly competitive for a future generation of THz detection systems.
Lasers and Optics Applied Physics B a.a. kosterev 1,✉ r.f. curl 1 f.k. tittel 1 m. rochat 2 m. be... more Lasers and Optics Applied Physics B a.a. kosterev 1,✉ r.f. curl 1 f.k. tittel 1 m. rochat 2 m. beck 2 d. hofstetter 2 j. faist 2
Recent advances in quantum-cascade (QC) laser active-region design are reviewed. Based on a rate ... more Recent advances in quantum-cascade (QC) laser active-region design are reviewed. Based on a rate equation model of the active region, we show why new gain regions based on a two-phonon resonance or a bound-to-continuum transition exhibit significantly better performance than the traditional design based on a three-quantum-well active region. Threshold current densities as low as 3 kA/cm 2 at = 300 K, operation with a peak power of 90 mW at 425 K, single-mode high-power operation up to temperatures above 330 K at 16 m and continuous wave operation up to = 311 K are demonstrated. QC lasers able to operate at high duty cycles (50%) on a Peltier cooler were used in a demonstration of a 300-MHz free-space optical link between two buildings separated by 350 m.
We present here a semiconductor injection laser operating in continuous wave with an emission cov... more We present here a semiconductor injection laser operating in continuous wave with an emission covering more than one octave in frequency, and displaying homogeneous power distribution among the lasing modes. The gain medium is based on a heterogeneous quantum cascade structure operating in the THz range. Laser emission in continuous wave takes place from 1.64 THz to 3.35 THz with optical powers in the mW range and more than 80 modes above threshold. Free-running beatnote investigations on narrow waveguides with linewidths of 980 Hz limited by jitter indicate frequency comb operation on a spectral bandwidth as wide as 624 GHz, making such devices ideal candidates for octave-spanning semiconductor-laser-based THz frequency combs. A broadband gain medium is desirable for a wide range of applications in laser science like widely tunable sources employing on-chip tuning [1, 2, 3], external cavity [4, 5, 6], or ultrashort pulse lasers [7, 8]. Broad gain is especially interesting when combined with locking techniques which enable the access to comb operation. Frequency combs act as rulers in the frequency domain and are realized starting either from a short-pulse mode-locked laser [9], or via non-linear processes [10, 11]. Combs have been demonstrated in the visible [12], Mid-Infrared (Mid-IR) 1
We present photoacoustic (PA) spectroscopy measurements of carbon dioxide, methanol, and ammonia.... more We present photoacoustic (PA) spectroscopy measurements of carbon dioxide, methanol, and ammonia. The light source for the excitation was a single-mode quantum cascade distributed-feedback laser, which was operated in pulsed mode at moderate duty cycle and slightly below room temperature. Temperature tuning resulted in a typical wavelength range of 3 cm 21 at a linewidth of 0.2 cm 21. The setup was based on a Herriott multipass arrangement around the PA cell; the cell was equipped with a radial 16-microphone array to increase sensitivity. Despite the relatively small average laser power, the ammonia detection limit was 300 parts in 10 9 by volume.
... The latter plays the role of injector on one side of the active region and on the other that ... more ... The latter plays the role of injector on one side of the active region and on the other that ... and j (4 in our case) is the number of optical phonon emissions that an electron needs to ... obtain an estimated in fair agreement with the experimental values in the 1080 K temperature range ...
... As displayed in Fig. 2(a), the luminescence spectrum at 10 K for light polarized in a plane p... more ... As displayed in Fig. 2(a), the luminescence spectrum at 10 K for light polarized in a plane perpendicular to the layers shows a peak at a photon energy hv=245 meV, somewhat lower than our calculated value for the transition energy un-der bias,&amp;#x27;E3,=275 meV. ...
A portable, stand-alone, real-time THz imaging system for high resolution is presented. The total... more A portable, stand-alone, real-time THz imaging system for high resolution is presented. The total weight of the apparatus is less than 15 kg and its physical dimension is of approximately (65 cm)3. A quantum cascade laser emitting at 3.4 THz based on a third-order distributed feedback cavity is used as radiation source for transmission and reflection imaging modes. We report real-time THz imaging with a bolometric camera operating at 15 Hz producing movies with a resolution of 120 x 160 pixels. With the help of a Stirling motor cryocooler the laser operates in continuous-wave at 40 K with more than 1 mW output power and less than 300 mW of power consumption. We were able to image small objects employing refractive elements that we manufactured in high density polyethylene achieving a resolution of twice the wavelength.
1996 54th Annual Device Research Conference Digest
Quantum Cascade (QC) lasers represent a fundamentally different semiconductor light-source based ... more Quantum Cascade (QC) lasers represent a fundamentally different semiconductor light-source based on the unipolar injection of carriers and on intersubband transitions between confined quantum states electrically pumped by resonant tunneling. In this paper QC lasers operating in the 9-11 μm infrared region are reported for the first time. Semiconductor lasers in the 8-13 μm atmospheric window are important for a wide range of applications from environmental sensing to industrial process control. In addition this work, combined with previous reports at shorter wavelengths, demonstrates that QC lasers are ideally suited to cover a wide spectral range by appropriate tailoring of the layer thickness using the same technologically advanced heterostructure material rather than low-band-gap semiconductors
2008 Conference on Lasers and Electro-Optics, 2008
Vincenzo Spagnolo INFM Regional Laboratory LIT 3 and Dipartimento Interateneo di FisicaM.Merlin... more Vincenzo Spagnolo INFM Regional Laboratory LIT 3 and Dipartimento Interateneo di FisicaM.Merlin , Politecnico di Bari, via Amendola 173, 70126 Bari, Italy ... Abstract: We have measured the electronic temperature of the upper laser level (TE ... At the present stage ...
Using terahertz time-domain spectroscopy we investigate how quantum, magnetic and electrostatic c... more Using terahertz time-domain spectroscopy we investigate how quantum, magnetic and electrostatic confinement alters the photoconductivity of nanostructured semiconductors. In 2.0 THz and 2.9THz GaAs/AlGaAs quantum cascade structures under a magnetic field we observe transitions from the 1s to 2p- or 2p+ magneto-exciton states. The electron cyclotron resonance is prominent at high excitation fluence. Additionally, we report that the conductivity of photoexcited electrons in nanoporous InP honeycombs obeys the Drude model of free-carrier absorption, while the dark conductivity does not. This finding can be explained as a result of surface band bending spatially separating photoexcited electrons and holes, and also accounts for the long electron recombination lifetime (exceeding 100 ns) at low temperature.
Physica E: Low-dimensional Systems and Nanostructures, 2002
Si/SiGe quantum cascade structure of 3×4 periods show well-resolved intersubband electroluminesce... more Si/SiGe quantum cascade structure of 3×4 periods show well-resolved intersubband electroluminescence, whose nonradiative lifetimes are found to depend strongly on the design of the quantum well structure, and are shown to reach values comparable to that of an equivalent GaInAs/AlInAs laser structure. Problems that need to be overcome for the realization of a Si/SiGe quantum cascade laser are discussed in
Quantum-cascade distributed-feedback lasers (QC-DFB) with a grating close to the active region ar... more Quantum-cascade distributed-feedback lasers (QC-DFB) with a grating close to the active region are reported. Feedback is provided by the grating in a refractive index-dominated coupling scheme. Reliable single-mode emission at em 5.4 m with a side-mode suppression ratio (SMSR) 30 dB is observed. The laser is continuously tunable over 40 nm with a coefficient of 1=1T 0.37 nm/K in the temperature range from 200 K to 300 K. Comparison with Fabry-Perot QC lasers shows an overall improved performance of QC-DFB lasers.
Intersubband absorption measurements on two nominally undoped AlGaN/GaN-based high-electron-mobil... more Intersubband absorption measurements on two nominally undoped AlGaN/GaN-based high-electron-mobility transistors with different Al compositions in the barrier layer are presented. The first transistor with a barrier consisting of Al 0.6 Ga 0.4 N showed an absorption peak at 247 meV ͑1973 cm Ϫ1 ͒ with a full width at half maximum ͑FWHM͒ of 126 meV, while the second device utilizing an Al 0.8 Ga 0.2 N barrier had its peak at 306 meV ͑2447 cm Ϫ1 ͒ with a FWHM of 86 meV. Self-consistently computed potentials and intersubband transition energies showed good agreement with the experimental findings, and therefore confirmed previously published values for the internal piezoelectric field in such structures.
strained si nanowires are among the most promising transistor structures for implementation in ve... more strained si nanowires are among the most promising transistor structures for implementation in very large-scale integration due to of their superior electrostatic control and enhanced transport properties. Realizing even higher strain levels within such nanowires are thus one of the current challenges in microelectronics. Here we achieve 4.5% of elastic strain (7.6 GPa uniaxial tensile stress) in 30 nm wide si nanowires, which considerably exceeds the limit that can be obtained using siGe-based virtual substrates. our approach is based on strain accumulation mechanisms in suspended dumbbell-shaped bridges patterned on strained si-on-insulator, and is compatible with complementary metal oxide semiconductor fabrication. Potentially, this method can be applied to any tensile prestrained layer, provided the layer can be released from the substrate, enabling the fabrication of a variety of strained semiconductors with unique properties for applications in nanoelectronics, photonics and photovoltaics. This method also opens up opportunities for research on strained materials.
The link between the inversion gain of quantum cascade structures and the Bloch gain in periodic ... more The link between the inversion gain of quantum cascade structures and the Bloch gain in periodic superlattices is presented. The proposed theoretical model based on the density matrix formalism is able to treat the gain mechanism of the Bloch oscillator and Quantum cascade laser on the same footing by taking into account in-plane momentum relaxation. The model predicts a dispersive contribution in addition to the (usual) population-inversion-dependent intersubband gain in quantum cascade structures and-in the absence of inversion-provides the quantum mechanical description for the dispersive gain in superlattices. It corroborates the predictions of the semi-classical miniband picture, according to which gain is predicted for photon energies lower than the Bloch oscillation frequency, whereas net absorption is expected at higher photon energies, as a description which is valid in the high-temperature limit. A red-shift of the amplified emission with respect to the resonant transition energy results from the dispersive gain contribution in any intersubband transition, for which the population inversion is small.
Physica E: Low-dimensional Systems and Nanostructures, 2008
We report simulations and experimental results of THz QCLs with quasi-periodic resonators based o... more We report simulations and experimental results of THz QCLs with quasi-periodic resonators based on a Fibonacci sequence.
This page was generated automatically upon download from the ETH Zurich Research Collection. For ... more This page was generated automatically upon download from the ETH Zurich Research Collection. For more information please consult the Terms of use. ETH Library PAPER • OPEN ACCESS Enhanced current injection from a quantum well to a quantum dash in magnetic field To cite this article: Gian L Paravicini-Bagliani et al 2014 New J. Phys. 16 083029 View the article online for updates and enhancements. Recent citations Carrier transfer efficiency and its influence on emission properties of telecom wavelength InP-based quantum dotquantum well structures Wojciech Rudno-Rudziski et al-Carrier diffusion as a measure of carrier/exciton transfer rate in InAs/InGaAsP/InP hybrid quantum dot-quantum well structures emitting at telecom spectral range W. Rudno-Rudziski et al-Carrier delocalization in InAs/InGaAlAs/InP quantum-dash-based tunnel injection system for 1.55 µm emission W. Rudno-Rudziski et al
Pulsed single mode operation of distributed feedback quantum cascade lasers is reported above roo... more Pulsed single mode operation of distributed feedback quantum cascade lasers is reported above room temperature at both 5.4 and 8 μm wavelengths. Peak optical powers up to 60 mW at 300 K are obtained with a tuning range of ∼60 nm from 100 to ∼320 K. The linewidth is limited by thermal drift during the pulse with a typical value of 0.3 cm−1 for a 10 ns long pulse at 300 K.
We report on the development of nanowire-based field-effect transistors operating as high sensiti... more We report on the development of nanowire-based field-effect transistors operating as high sensitivity terahertz (THz) detectors. By feeding the 1.5 THz radiation field of a quantum cascade laser (QCL) at the gate-source electrodes with a wide band dipole antenna, we record a photovoltage signal corresponding to responsivity values >10 V/W, with impressive noise equivalent power levels <6 × 10−11 W/√Hz at room temperature and a wide modulation bandwidth. The potential scalability to even higher frequencies and the technological feasibility of realizing multi-pixel arrays coupled with QCL sources make the proposed technology highly competitive for a future generation of THz detection systems.
Lasers and Optics Applied Physics B a.a. kosterev 1,✉ r.f. curl 1 f.k. tittel 1 m. rochat 2 m. be... more Lasers and Optics Applied Physics B a.a. kosterev 1,✉ r.f. curl 1 f.k. tittel 1 m. rochat 2 m. beck 2 d. hofstetter 2 j. faist 2
Recent advances in quantum-cascade (QC) laser active-region design are reviewed. Based on a rate ... more Recent advances in quantum-cascade (QC) laser active-region design are reviewed. Based on a rate equation model of the active region, we show why new gain regions based on a two-phonon resonance or a bound-to-continuum transition exhibit significantly better performance than the traditional design based on a three-quantum-well active region. Threshold current densities as low as 3 kA/cm 2 at = 300 K, operation with a peak power of 90 mW at 425 K, single-mode high-power operation up to temperatures above 330 K at 16 m and continuous wave operation up to = 311 K are demonstrated. QC lasers able to operate at high duty cycles (50%) on a Peltier cooler were used in a demonstration of a 300-MHz free-space optical link between two buildings separated by 350 m.
We present here a semiconductor injection laser operating in continuous wave with an emission cov... more We present here a semiconductor injection laser operating in continuous wave with an emission covering more than one octave in frequency, and displaying homogeneous power distribution among the lasing modes. The gain medium is based on a heterogeneous quantum cascade structure operating in the THz range. Laser emission in continuous wave takes place from 1.64 THz to 3.35 THz with optical powers in the mW range and more than 80 modes above threshold. Free-running beatnote investigations on narrow waveguides with linewidths of 980 Hz limited by jitter indicate frequency comb operation on a spectral bandwidth as wide as 624 GHz, making such devices ideal candidates for octave-spanning semiconductor-laser-based THz frequency combs. A broadband gain medium is desirable for a wide range of applications in laser science like widely tunable sources employing on-chip tuning [1, 2, 3], external cavity [4, 5, 6], or ultrashort pulse lasers [7, 8]. Broad gain is especially interesting when combined with locking techniques which enable the access to comb operation. Frequency combs act as rulers in the frequency domain and are realized starting either from a short-pulse mode-locked laser [9], or via non-linear processes [10, 11]. Combs have been demonstrated in the visible [12], Mid-Infrared (Mid-IR) 1
We present photoacoustic (PA) spectroscopy measurements of carbon dioxide, methanol, and ammonia.... more We present photoacoustic (PA) spectroscopy measurements of carbon dioxide, methanol, and ammonia. The light source for the excitation was a single-mode quantum cascade distributed-feedback laser, which was operated in pulsed mode at moderate duty cycle and slightly below room temperature. Temperature tuning resulted in a typical wavelength range of 3 cm 21 at a linewidth of 0.2 cm 21. The setup was based on a Herriott multipass arrangement around the PA cell; the cell was equipped with a radial 16-microphone array to increase sensitivity. Despite the relatively small average laser power, the ammonia detection limit was 300 parts in 10 9 by volume.
... The latter plays the role of injector on one side of the active region and on the other that ... more ... The latter plays the role of injector on one side of the active region and on the other that ... and j (4 in our case) is the number of optical phonon emissions that an electron needs to ... obtain an estimated in fair agreement with the experimental values in the 1080 K temperature range ...
... As displayed in Fig. 2(a), the luminescence spectrum at 10 K for light polarized in a plane p... more ... As displayed in Fig. 2(a), the luminescence spectrum at 10 K for light polarized in a plane perpendicular to the layers shows a peak at a photon energy hv=245 meV, somewhat lower than our calculated value for the transition energy un-der bias,&amp;#x27;E3,=275 meV. ...
A portable, stand-alone, real-time THz imaging system for high resolution is presented. The total... more A portable, stand-alone, real-time THz imaging system for high resolution is presented. The total weight of the apparatus is less than 15 kg and its physical dimension is of approximately (65 cm)3. A quantum cascade laser emitting at 3.4 THz based on a third-order distributed feedback cavity is used as radiation source for transmission and reflection imaging modes. We report real-time THz imaging with a bolometric camera operating at 15 Hz producing movies with a resolution of 120 x 160 pixels. With the help of a Stirling motor cryocooler the laser operates in continuous-wave at 40 K with more than 1 mW output power and less than 300 mW of power consumption. We were able to image small objects employing refractive elements that we manufactured in high density polyethylene achieving a resolution of twice the wavelength.
1996 54th Annual Device Research Conference Digest
Quantum Cascade (QC) lasers represent a fundamentally different semiconductor light-source based ... more Quantum Cascade (QC) lasers represent a fundamentally different semiconductor light-source based on the unipolar injection of carriers and on intersubband transitions between confined quantum states electrically pumped by resonant tunneling. In this paper QC lasers operating in the 9-11 μm infrared region are reported for the first time. Semiconductor lasers in the 8-13 μm atmospheric window are important for a wide range of applications from environmental sensing to industrial process control. In addition this work, combined with previous reports at shorter wavelengths, demonstrates that QC lasers are ideally suited to cover a wide spectral range by appropriate tailoring of the layer thickness using the same technologically advanced heterostructure material rather than low-band-gap semiconductors
2008 Conference on Lasers and Electro-Optics, 2008
Vincenzo Spagnolo INFM Regional Laboratory LIT 3 and Dipartimento Interateneo di FisicaM.Merlin... more Vincenzo Spagnolo INFM Regional Laboratory LIT 3 and Dipartimento Interateneo di FisicaM.Merlin , Politecnico di Bari, via Amendola 173, 70126 Bari, Italy ... Abstract: We have measured the electronic temperature of the upper laser level (TE ... At the present stage ...
Using terahertz time-domain spectroscopy we investigate how quantum, magnetic and electrostatic c... more Using terahertz time-domain spectroscopy we investigate how quantum, magnetic and electrostatic confinement alters the photoconductivity of nanostructured semiconductors. In 2.0 THz and 2.9THz GaAs/AlGaAs quantum cascade structures under a magnetic field we observe transitions from the 1s to 2p- or 2p+ magneto-exciton states. The electron cyclotron resonance is prominent at high excitation fluence. Additionally, we report that the conductivity of photoexcited electrons in nanoporous InP honeycombs obeys the Drude model of free-carrier absorption, while the dark conductivity does not. This finding can be explained as a result of surface band bending spatially separating photoexcited electrons and holes, and also accounts for the long electron recombination lifetime (exceeding 100 ns) at low temperature.
Physica E: Low-dimensional Systems and Nanostructures, 2002
Si/SiGe quantum cascade structure of 3×4 periods show well-resolved intersubband electroluminesce... more Si/SiGe quantum cascade structure of 3×4 periods show well-resolved intersubband electroluminescence, whose nonradiative lifetimes are found to depend strongly on the design of the quantum well structure, and are shown to reach values comparable to that of an equivalent GaInAs/AlInAs laser structure. Problems that need to be overcome for the realization of a Si/SiGe quantum cascade laser are discussed in
Quantum-cascade distributed-feedback lasers (QC-DFB) with a grating close to the active region ar... more Quantum-cascade distributed-feedback lasers (QC-DFB) with a grating close to the active region are reported. Feedback is provided by the grating in a refractive index-dominated coupling scheme. Reliable single-mode emission at em 5.4 m with a side-mode suppression ratio (SMSR) 30 dB is observed. The laser is continuously tunable over 40 nm with a coefficient of 1=1T 0.37 nm/K in the temperature range from 200 K to 300 K. Comparison with Fabry-Perot QC lasers shows an overall improved performance of QC-DFB lasers.
Intersubband absorption measurements on two nominally undoped AlGaN/GaN-based high-electron-mobil... more Intersubband absorption measurements on two nominally undoped AlGaN/GaN-based high-electron-mobility transistors with different Al compositions in the barrier layer are presented. The first transistor with a barrier consisting of Al 0.6 Ga 0.4 N showed an absorption peak at 247 meV ͑1973 cm Ϫ1 ͒ with a full width at half maximum ͑FWHM͒ of 126 meV, while the second device utilizing an Al 0.8 Ga 0.2 N barrier had its peak at 306 meV ͑2447 cm Ϫ1 ͒ with a FWHM of 86 meV. Self-consistently computed potentials and intersubband transition energies showed good agreement with the experimental findings, and therefore confirmed previously published values for the internal piezoelectric field in such structures.
strained si nanowires are among the most promising transistor structures for implementation in ve... more strained si nanowires are among the most promising transistor structures for implementation in very large-scale integration due to of their superior electrostatic control and enhanced transport properties. Realizing even higher strain levels within such nanowires are thus one of the current challenges in microelectronics. Here we achieve 4.5% of elastic strain (7.6 GPa uniaxial tensile stress) in 30 nm wide si nanowires, which considerably exceeds the limit that can be obtained using siGe-based virtual substrates. our approach is based on strain accumulation mechanisms in suspended dumbbell-shaped bridges patterned on strained si-on-insulator, and is compatible with complementary metal oxide semiconductor fabrication. Potentially, this method can be applied to any tensile prestrained layer, provided the layer can be released from the substrate, enabling the fabrication of a variety of strained semiconductors with unique properties for applications in nanoelectronics, photonics and photovoltaics. This method also opens up opportunities for research on strained materials.
Uploads
Papers by J. Faist