In this work we employ dibromocarbene (DBC) radicals to covalently functionalize solution-exfolia... more In this work we employ dibromocarbene (DBC) radicals to covalently functionalize solution-exfoliated graphene via the formation of dibromocyclopropyl adducts. This is achieved using a basic-aqueous/organic bi-phasic reaction mixture to decompose the dibromocarbene precursor, bromoform, in conjunction with a phase transfer catalyst to facilitate ylide formation and carbene migration to graphene substrates. DBC-functionalized graphene (DBC-graphene) was characterized using a range of spectroscopic and analytical techniques to confirm the covalent nature of functionalization. Modified optical and electronic properties of DBC-graphene were investigated using UV-vis spectroscopy, analysis of electrical I-V transport properties and using non-contact terahertz time-domain spectroscopy (TTDS). The implications of the carbene functionalization of graphene are considered in the context of scalable radical functionalization methodologies for bulk-scale graphene processing and controlled band-gap manipulation of graphene.
This paper reviews metrology aspects of terahertz time-domain spectroscopy. Noise is discussed to... more This paper reviews metrology aspects of terahertz time-domain spectroscopy. Noise is discussed together with its effects on system performance, including frequency-dependent dynamic range, signal-to noise ratio, and the measurement bandwidth. Sources of uncertainties are addressed, as are measurement errors arising from system design and from interactions with the object under test. Finally, techniques of system calibration are described. Commonly encountered issues are addressed and simple practical solutions suggested. Existing literature on the subject is reviewed.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The area of terahertz science and applications has grown dramatically in the last 30 years. Instr... more The area of terahertz science and applications has grown dramatically in the last 30 years. Instrumental platforms for THz measurements have also proliferated, and now include laser-based, electronic, opto-electronic, and microwave photonics devices. As the field matured, metrology and standardization have gained focused attention, resulting in an increasing number of publications and a book devoted to the subject. However, these have been primarily focused on photonic-based free-space techniques and their particular demands and issues. This paper presents a brief review of metrology requirements for active THz electronic devices, the available instrumentation, state of the art, and challenges.
ABSTRACT A variety of fabrics are examined using THz time-domain spectroscopy. Different types of... more ABSTRACT A variety of fabrics are examined using THz time-domain spectroscopy. Different types of textiles are shown to have different THz optical properties, which may be employed to combat textile counterfeiting.
A dense set of solid solution crystals GaSe1-xSx is examined using THz-TDS. Evolution of phonon a... more A dense set of solid solution crystals GaSe1-xSx is examined using THz-TDS. Evolution of phonon absorption peaks with the increase of S content is shown to have complex transformation, which should be considered in the design of dispersion equations for THz applications.
ABSTRACT Gallium Selenide crystals having compositions modified with a range of elements are inve... more ABSTRACT Gallium Selenide crystals having compositions modified with a range of elements are investigated using THz time-domain spectroscopy, Raman, FTIR and ellipsometry. The optical properties are related to modifications in the crystal structure.
A variety of solid solution GaSe1-xSx crystals are examined using THz time-domain spectroscopy. D... more A variety of solid solution GaSe1-xSx crystals are examined using THz time-domain spectroscopy. Different types of crystals are shown to have different THz optical properties and anisotropy, which may be employed for THz applications.
The emission spectra and the lifetimes of the lasing transition 4 I 13/2-4 I 15/2 in Er 3ϩ-doped ... more The emission spectra and the lifetimes of the lasing transition 4 I 13/2-4 I 15/2 in Er 3ϩ-doped TeO 2-ZnO-Na 2 O ternary glasses have been studied. The investigation includes two main studies: The first part discusses the Raman spectroscopic analysis of the host glass structure. In the second part, we explain the dependence of Er 3ϩ-ion photoluminescence near 1500 nm on OH Ϫ-ion concentration. The influence of the concentrations of Er 2 O 3 and the glass structure modifiers ͑ZnO, Na 2 O͒ on the lifetimes of 4 I 13/2 level and line shape of the emission spectra has been analyzed. It was observed that the increasing concentrations of Er 3ϩ ions resulted in spectral broadening as a consequence of Er 3ϩ being distributed in the glass structure. The measured lifetimes of 4 I 13/2 emission vary between 4.5 and 7.8 ms and strongly depend on OH-ion concentrations. The structural origin of the spectral broadening of the Er emission line is particularly discussed by analyzing the spectral components in the tellurite, modified silicate, and fluoride glass hosts. The number of spectral components at room temperature in Er-doped TeO 2 , silicate, and fluoride glasses are compared, and the dependence of line strengths and site-to-site variation of the rare-earth ions on the structure of each glass is also explained. The unusually large broadening of the OH Ϫ band in the TeO 2 family of glasses is analyzed in the context of the tellurite glass structure.
Cadmium mixed halide glasses exhibit lower peak phonon energy than conventional fluorozirconate g... more Cadmium mixed halide glasses exhibit lower peak phonon energy than conventional fluorozirconate glasses. New glass compositions doped with Pr3+-ions were fabricated using controlled atmosphere melting and casting techniques. The optical properties of new bulk glasses were studied by spectruscopic techniques. The significance of an empirically derived total loss curve for bulk glass is examined for the design of a 1.3 µm amplifier. The concentration effects of Pr3+-ions as a dopant in the glass were studied, and its absorption cross-section measured to establish the ground state absorption in bulk glass. The thermal stability of mixed halide glasses was studied by differential scanning calorimetry. and an appraisal of their devitrification behaviour is presented.
Wireless bridges operating at THz frequencies have drawn a lot of attention in recent years. This... more Wireless bridges operating at THz frequencies have drawn a lot of attention in recent years. This application requires multiple optical local oscillators (LOs) throughout the link and, hence, the accumulated phase noise may impose a major challenge for its practical implementation. Of all the techniques to mitigate phase noise, single sideband (SSB) modulation is a very promising candidate due to its simple implementation. In this paper, we show, for the first time, the transmission of a 6 GBd SSB QPSK signal at 250 GHz and investigate the impact of laser phase noise on the quality of the THz signal. The performance of the system is investigated by digitally tuning the linewidth of the optical local oscillator up to 10 MHz. The results show no observable penalty associated with increasing linewidth, confirming the validity of SSB for applications where multiple domain conversions are required.
Abstract : We investigated the possibility of determining the nonlinear properties of Si, GaAs an... more Abstract : We investigated the possibility of determining the nonlinear properties of Si, GaAs and GaSex-1Sx and other nonlinear optical crystals in the FIRand THz regimes using the classic Maker Fringe and Z-scan techniques. The Z-scan measurements were conducted successfully, in both the FIRand THz regimes, and the measurement results in the FIR were found to be in reasonable agreement with the available literature [7, 8, 9]. Wecan conclude that multi-photon absorption in the FIR is no more an impediment to pumping, GaSe based, nonlinear frequency conversiondevices that in the near-IR.
Cadmium mixed halide glasses have been recently identified as a potential low-phonon energy host ... more Cadmium mixed halide glasses have been recently identified as a potential low-phonon energy host for 1.3µm Pr3+-doped optical fibre amplifier. We report the crystallization behaviour of the mixed halide glasses while reheated above their glass transition temperature. The effect of impurities in the starting raw materials on the quality of the bulk glass is reported. The OH- absorption was monitored by FTIR technique, and related to the lifetime of the 1G4 excited state in Pr3+-doped glass. The thermal stability of the glass was studied from heat treatment data using a differential scanning calorimeter.
In this work we employ dibromocarbene (DBC) radicals to covalently functionalize solution-exfolia... more In this work we employ dibromocarbene (DBC) radicals to covalently functionalize solution-exfoliated graphene via the formation of dibromocyclopropyl adducts. This is achieved using a basic-aqueous/organic bi-phasic reaction mixture to decompose the dibromocarbene precursor, bromoform, in conjunction with a phase transfer catalyst to facilitate ylide formation and carbene migration to graphene substrates. DBC-functionalized graphene (DBC-graphene) was characterized using a range of spectroscopic and analytical techniques to confirm the covalent nature of functionalization. Modified optical and electronic properties of DBC-graphene were investigated using UV-vis spectroscopy, analysis of electrical I-V transport properties and using non-contact terahertz time-domain spectroscopy (TTDS). The implications of the carbene functionalization of graphene are considered in the context of scalable radical functionalization methodologies for bulk-scale graphene processing and controlled band-gap manipulation of graphene.
This paper reviews metrology aspects of terahertz time-domain spectroscopy. Noise is discussed to... more This paper reviews metrology aspects of terahertz time-domain spectroscopy. Noise is discussed together with its effects on system performance, including frequency-dependent dynamic range, signal-to noise ratio, and the measurement bandwidth. Sources of uncertainties are addressed, as are measurement errors arising from system design and from interactions with the object under test. Finally, techniques of system calibration are described. Commonly encountered issues are addressed and simple practical solutions suggested. Existing literature on the subject is reviewed.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
The area of terahertz science and applications has grown dramatically in the last 30 years. Instr... more The area of terahertz science and applications has grown dramatically in the last 30 years. Instrumental platforms for THz measurements have also proliferated, and now include laser-based, electronic, opto-electronic, and microwave photonics devices. As the field matured, metrology and standardization have gained focused attention, resulting in an increasing number of publications and a book devoted to the subject. However, these have been primarily focused on photonic-based free-space techniques and their particular demands and issues. This paper presents a brief review of metrology requirements for active THz electronic devices, the available instrumentation, state of the art, and challenges.
ABSTRACT A variety of fabrics are examined using THz time-domain spectroscopy. Different types of... more ABSTRACT A variety of fabrics are examined using THz time-domain spectroscopy. Different types of textiles are shown to have different THz optical properties, which may be employed to combat textile counterfeiting.
A dense set of solid solution crystals GaSe1-xSx is examined using THz-TDS. Evolution of phonon a... more A dense set of solid solution crystals GaSe1-xSx is examined using THz-TDS. Evolution of phonon absorption peaks with the increase of S content is shown to have complex transformation, which should be considered in the design of dispersion equations for THz applications.
ABSTRACT Gallium Selenide crystals having compositions modified with a range of elements are inve... more ABSTRACT Gallium Selenide crystals having compositions modified with a range of elements are investigated using THz time-domain spectroscopy, Raman, FTIR and ellipsometry. The optical properties are related to modifications in the crystal structure.
A variety of solid solution GaSe1-xSx crystals are examined using THz time-domain spectroscopy. D... more A variety of solid solution GaSe1-xSx crystals are examined using THz time-domain spectroscopy. Different types of crystals are shown to have different THz optical properties and anisotropy, which may be employed for THz applications.
The emission spectra and the lifetimes of the lasing transition 4 I 13/2-4 I 15/2 in Er 3ϩ-doped ... more The emission spectra and the lifetimes of the lasing transition 4 I 13/2-4 I 15/2 in Er 3ϩ-doped TeO 2-ZnO-Na 2 O ternary glasses have been studied. The investigation includes two main studies: The first part discusses the Raman spectroscopic analysis of the host glass structure. In the second part, we explain the dependence of Er 3ϩ-ion photoluminescence near 1500 nm on OH Ϫ-ion concentration. The influence of the concentrations of Er 2 O 3 and the glass structure modifiers ͑ZnO, Na 2 O͒ on the lifetimes of 4 I 13/2 level and line shape of the emission spectra has been analyzed. It was observed that the increasing concentrations of Er 3ϩ ions resulted in spectral broadening as a consequence of Er 3ϩ being distributed in the glass structure. The measured lifetimes of 4 I 13/2 emission vary between 4.5 and 7.8 ms and strongly depend on OH-ion concentrations. The structural origin of the spectral broadening of the Er emission line is particularly discussed by analyzing the spectral components in the tellurite, modified silicate, and fluoride glass hosts. The number of spectral components at room temperature in Er-doped TeO 2 , silicate, and fluoride glasses are compared, and the dependence of line strengths and site-to-site variation of the rare-earth ions on the structure of each glass is also explained. The unusually large broadening of the OH Ϫ band in the TeO 2 family of glasses is analyzed in the context of the tellurite glass structure.
Cadmium mixed halide glasses exhibit lower peak phonon energy than conventional fluorozirconate g... more Cadmium mixed halide glasses exhibit lower peak phonon energy than conventional fluorozirconate glasses. New glass compositions doped with Pr3+-ions were fabricated using controlled atmosphere melting and casting techniques. The optical properties of new bulk glasses were studied by spectruscopic techniques. The significance of an empirically derived total loss curve for bulk glass is examined for the design of a 1.3 µm amplifier. The concentration effects of Pr3+-ions as a dopant in the glass were studied, and its absorption cross-section measured to establish the ground state absorption in bulk glass. The thermal stability of mixed halide glasses was studied by differential scanning calorimetry. and an appraisal of their devitrification behaviour is presented.
Wireless bridges operating at THz frequencies have drawn a lot of attention in recent years. This... more Wireless bridges operating at THz frequencies have drawn a lot of attention in recent years. This application requires multiple optical local oscillators (LOs) throughout the link and, hence, the accumulated phase noise may impose a major challenge for its practical implementation. Of all the techniques to mitigate phase noise, single sideband (SSB) modulation is a very promising candidate due to its simple implementation. In this paper, we show, for the first time, the transmission of a 6 GBd SSB QPSK signal at 250 GHz and investigate the impact of laser phase noise on the quality of the THz signal. The performance of the system is investigated by digitally tuning the linewidth of the optical local oscillator up to 10 MHz. The results show no observable penalty associated with increasing linewidth, confirming the validity of SSB for applications where multiple domain conversions are required.
Abstract : We investigated the possibility of determining the nonlinear properties of Si, GaAs an... more Abstract : We investigated the possibility of determining the nonlinear properties of Si, GaAs and GaSex-1Sx and other nonlinear optical crystals in the FIRand THz regimes using the classic Maker Fringe and Z-scan techniques. The Z-scan measurements were conducted successfully, in both the FIRand THz regimes, and the measurement results in the FIR were found to be in reasonable agreement with the available literature [7, 8, 9]. Wecan conclude that multi-photon absorption in the FIR is no more an impediment to pumping, GaSe based, nonlinear frequency conversiondevices that in the near-IR.
Cadmium mixed halide glasses have been recently identified as a potential low-phonon energy host ... more Cadmium mixed halide glasses have been recently identified as a potential low-phonon energy host for 1.3µm Pr3+-doped optical fibre amplifier. We report the crystallization behaviour of the mixed halide glasses while reheated above their glass transition temperature. The effect of impurities in the starting raw materials on the quality of the bulk glass is reported. The OH- absorption was monitored by FTIR technique, and related to the lifetime of the 1G4 excited state in Pr3+-doped glass. The thermal stability of the glass was studied from heat treatment data using a differential scanning calorimeter.
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