Exciton dynamics studied via internal THz transitions

Kaindl, Robert A.; Hägele, D.; Carnahan, M. A.; Lövenich, R.; Chemla, D. S.

doi:10.1002/pssb.200303161

Cited by 14 publications

(8 citation statements)

References 13 publications

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“…The first detailed study on the dynamics of the formation and ionization of excitons was performed by Kaindl et al (2003) on GaAs quantum wells. Later works by this group incorporated a more elaborate analysis in order to retrieve precise quantitative figures on exciton and plasma densities ).…”

Section: Intraexcitonic Transitionsmentioning

confidence: 99%

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

et al. 2011

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Time-resolved, pulsed terahertz spectroscopy has developed into a powerful tool to study charge carrier dynamics in semiconductors and semiconductor structures over the past decades. Covering the energy range from a few to about 100 meV, terahertz radiation is sensitive to the response of charge quasiparticles, e.g., free carriers, polarons, and excitons. The distinct spectral signatures of these different quasiparticles in the THz range allow their discrimination and characterization using pulsed THz radiation. This frequency region is also well suited for the study of phonon resonances and intraband transitions in low-dimensional systems. Moreover, using a pump-probe scheme, it is possible to monitor the nonequilibrium time evolution of carriers and low-energy excitations with sub-ps time resolution. Being an all-optical technique, terahertz time-domain spectroscopy is contact-free and noninvasive and hence suited to probe the conductivity of, particularly, nanostructured materials that are difficult or impossible to access with other methods. The latest developments in the application of terahertz time-domain spectroscopy to bulk and nanostructured semiconductors are reviewed.

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Section: Intraexcitonic Transitionsmentioning

confidence: 99%

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

et al. 2011

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“…Over the last few years interest in using far-infrared radiation as a non-contact probe of the properties of various materials such as semiconductors [1,2,3], superconductors [4,5,6] and biological tissue [7,8] has grown considerably. This has been as a result of improvements in sources [9,10] and detectors [11] of terahertz (THz) frequency radiation, and the development of novel spectroscopic methods such as time domain spectroscopy [12,13].…”

Section: Introductionmentioning

confidence: 99%

“…By recording the electric field of a single cycle of terahertz radiation as function of time, the technique of time domain spectroscopy is capable of extremely sensitive measurements, especially in the far-infrared band. This technique represents a particularly powerful tool for studying the dynamics of weakly correlated systems in condensed matter physics, including excitons and Cooper pairs, which have binding energies observable in the THz region of the electromagnetic spectrum [3,6].…”

Section: Introductionmentioning

confidence: 99%

Three-dimensional carrier-dynamics simulation of terahertz emission from photoconductive switches

2005

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A semi-classical Monte Carlo model for studying three-dimensional carrier dynamics in photoconductive switches is presented. The model was used to simulate the process of photo-excitation in GaAs-based photoconductive antennas illuminated with pulses typical of mode-locked Ti:Sapphire lasers. We analysed the power and frequency bandwidth of THz radiation emitted from these devices as a function of bias voltage, pump pulse duration and pump pulse location. We show that the mechanisms limiting the THz power emitted from photoconductive switches fall into two regimes: when illuminated with short duration (< 40 fs) laser pulses the energy distribution of the Gaussian pulses constrains the emitted power, while for long (> 40 fs) pulses, screening is the primary power-limiting mechanism. A discussion of the dynamics of bias field screening in the gap region is presented. The emitted terahertz power was found to be enhanced when the exciting laser pulse was in close proximity to the anode of the photoconductive emitter, in agreement with experimental results. We show that this enhancement arises from the electric field distribution within the emitter combined with a difference in the mobilities of electrons and holes.

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“…The technique of THz time domain spectroscopy (TDS), 1,2 which has developed rapidly as a result of advances in ultra-short pulsed laser technology, now provides a very sensitive probe across the THz band. TDS is currently an invaluable tool in condensed matter physics 3,4,5 and macromolecular chemistry. 6,7 To date THz-TDS techniques have relied on linearly polarised emitters and detectors.…”

mentioning

confidence: 99%

Polarization-sensitive terahertz detection by multicontact photoconductive receivers

Castro-Camus

Lloyd‐Hughes

Johnston

et al. 2005

Applied Physics Letters

126

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We have developed a terahertz radiation detector that measures both the amplitude and polarisation of the electric field as a function of time. The device is a three-contact photoconductive receiver designed so that two orthogonal electric field components of an arbitrary polarised electromagnetic wave may be detected simultaneously. The detector was fabricated on Fe + ion-implanted InP. Polarisation-sensitive detection is demonstrated with an extinction ratio better than 100:1. This type of device will have immediate application in studies of birefringent and optically active materials in the far-infrared region of the spectrum.PACS numbers: 07.57.Kp , 07.57.Pt, 07.60.Fs, 42.25.Ja, 71.55.Eq , 78.20.Ek, 78.20.Fm The far-infrared, or terahertz (THz), region of the electromagnetic spectrum encompasses the energy range of many collective processes in condensed matter physics and macromolecular chemistry. However, in the past this spectral region has been relatively unexplored owing to a lack of bright radiation sources and appropriate detectors. The technique of THz time domain spectroscopy (TDS), 1,2 which has developed rapidly as a result of advances in ultra-short pulsed laser technology, now provides a very sensitive probe across the THz band. TDS is currently an invaluable tool in condensed matter physics 3,4,5 and macromolecular chemistry. 6,7To date THz-TDS techniques have relied on linearly polarised emitters and detectors. However, for spectroscopy of birefringent and optically active materials it is also important to measure the polarisation state of radiation before and after it has interacted with the material. Here we report on a detector that enables such a THz-TDS system to be realised.Vibrational circular dichroism (VCD) spectroscopy is a new technique which has substantial potential in the fields of macromolecular chemistry and structural biology. 8 Akin to the established technique of (ultraviolet) circular dichroism, VCD is used to analyse the structure of chiral molecules. It is predicted that VCD will be more powerful than conventional circular dichroism for stereo-chemical structure determination. 8 However the technique is currently limited by insensitive and narrow band spectrometers.Of particular interest to biochemists is the structure and function of proteins and nucleic acids. These chiral biomolecules have vibrational and librational modes in the THz region and the THz optical activity of these modes are starting to be studied experimentally. 9,10 THz frequency VCD is already finding application in fields as distinct as biochemical research 11 and astrobiology. 10 In the future the ability to perform VCD using a polarisation sensitive THz-TDS technique should enhance the bandwidth and sensitivity of measurements, and allow dynamic time-resolved studies to be performed.In order to perform polarisation sensitive THz-TDS, it is necessary to be able to measure two (preferably orthogonal) electric field components of a terahertz transient. Theoretically it is possible to do this using a ...

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Exciton dynamics studied via internal THz transitions

Cited by 14 publications

References 13 publications

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

Three-dimensional carrier-dynamics simulation of terahertz emission from photoconductive switches

Polarization-sensitive terahertz detection by multicontact photoconductive receivers

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