Longitudinal spatial hole burning in terahertz quantum cascade lasers

Kröll, J.; Darmo, J.; Unterrainer, K.; Dhillon, Sukhdeep; Sirtori, Carlo; Marcadet, X.; Calligaro, M.

doi:10.1063/1.2747185

Cited by 24 publications

(13 citation statements)

References 14 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Other THz studies on QCLs focused on gain dynamics below and above lasing threshold (Kuehn et al, 2008;Jukam et al, 2009), the charge carrier mobility and density (LloydHughes et al, 2009), observed spatial hole burning (Kroll, Darmo et al, 2007), spectral gain narrowing (Jukam et al, 2008), and identified the charge injection process from the injector layer into the upper laser state as being coherent, i.e., through resonant tunneling (Eickemeyer et al, 2002). …”

Section: Quantum Wellsmentioning

confidence: 99%

See 1 more Smart Citation

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

et al. 2011

View full text Add to dashboard Cite

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.

show abstract

Section: Quantum Wellsmentioning

confidence: 99%

“…Kroll, Darmo et al (2007) studied the polarization dynamics of AlGaAs/GaAs THz QCLs that lased at a frequency of 2.9 THz. The THz probe pulse was generated by a photoconductive antenna, coupled into the QCL waveguide and its transmission detected by EO sampling.…”

Section: Quantum Wellsmentioning

confidence: 99%

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

et al. 2011

View full text Add to dashboard Cite

show abstract

“…8,9 Recently, terahertz timedomain spectroscopy (TDS) has been shown to be a powerful technique to measure the gain spectra in terahertz QCLs. 10,11,12 Here, a broadband terahertz probe pulse is coupled into the QCL, and the electric field of the transmitted pulses is measured using electrooptic sampling. 13 In this letter terahertz TDS is used to investigate the line-width of the spectral gain as a function of current density.…”

mentioning

confidence: 99%

Investigation of spectral gain narrowing in quantum cascade lasers using terahertz time domain spectroscopy

Jukam¹,

Dhillon²,

Oustinov³

et al. 2008

Applied Physics Letters

View full text Add to dashboard Cite

2 AbstractThe spectral gain of bound-to-continuum terahertz quantum cascade lasers (QCLs) is measured as a function of current density using terahertz time-domain spectroscopy.During lasing action the full width at half maximum (FWHM) of the gain is found to monotonically decrease with increasing current density until lasing action stops at which point the FWHM reaches a minimum (0.22THz for a laser operating at 2.1THz).Bandstructure calculations show that the spectral gain narrowing is due to the alignment and misalignment of the injector with the active region as a function of the applied bias field.3 Important progress on terahertz quantum cascade lasers (QCLs) has been achieved in the last few years leading to long wavelength 1 , high power 2 , low current operation 3 , and working temperatures up to 178K 4 . In order to realize further improvements, a better understanding of the gain formation mechanism, and its limiting factors are needed. To this end it is necessary to perform detailed measurements of the gain including its spectral shape. Previous studies have been performed for mid-infraredQCLs. For these measurements, electro-luminescence from a non-lasing cavity is coupledinto an adjacent cavity that shows laser action. 5 However, in the terahertz regime such electro-luminescence based studies are difficult, because of the reduced spontaneous emission at longer wavelengths. Electro-luminescence from the laser cavity has also been used to provide information on upper state lifetimes of terahertz QCLs. 6 In this case to avoid the effect of laser emission, the electro-luminescence from the laser cavity must be collected from a cleaved edge running though the middle of the laser. 7 Multiple probe pulses coupled into the QCL's end facets can also be used to investigate the temporal dynamics of the gain. Coherent population transfer and gain saturation have been observed with this technique at mid-infrared frequencies. 8,9 Recently, terahertz timedomain spectroscopy (TDS) has been shown to be a powerful technique to measure the gain spectra in terahertz QCLs. 10,11,12 Here, a broadband terahertz probe pulse is coupled into the QCL, and the electric field of the transmitted pulses is measured using electrooptic sampling. 13In this letter terahertz TDS is used to investigate the line-width of the spectral gain as a function of current density. Two terahertz QCLs lasers with different bound-tocontinuum designs are studied. One laser emits at 2.1THz 14 and the other emits at 2.9THz. 15 For both devices, as the current density is increased from threshold, we observe a monotonic decrease of the full width at half maximum (FWHM) of the gain. After the 4 laser reaches maximum power, this gain narrowing increases sharply, until laser action ceases. By calculating the band structure for different bias fields, we show the gain narrowing is a consequence of a misalignment of the upper state of the laser transition with the injector miniband.The 2.1THz (2.9THz) sample has an active region thickness of 14µm (12µm), and a...

show abstract

“…16 Another possible mechanism affecting the 3D spatial distribution of the guided modes is gain guiding induced by an inhomogeneous current distribution in the plane. 17 To investigate further the possibility of gain guiding we deliberately forced a nonuniform current distribution in the device with a central slit by electrically biasing only one of the top metal pads. The effect is shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

Effect of transverse mode structure on the far field pattern of metal-metal terahertz quantum cascade lasers

Gellie

Maineult

Andronico

et al. 2008

Journal of Applied Physics

View full text Add to dashboard Cite

We elucidate the effects of the lateral mode structure on the far field pattern of metal-metal ridge-waveguide terahertz quantum cascade lasers. By introducing a 6-m-wide metal gap on the top metal contact, we suppress odd-parity lateral modes and drastically modify the far field pattern. Measurements are in good qualitative agreement with full three-dimensional finite-difference-time-domain modeling. Experimental evidence of nonuniform current pumping on the intensity distribution of the guided mode ͑and hence the far field pattern͒ is also presented and explained in terms of gain guiding.

show abstract

Longitudinal spatial hole burning in terahertz quantum cascade lasers

Cited by 24 publications

References 14 publications

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

Carrier dynamics in semiconductors studied with time-resolved terahertz spectroscopy

Investigation of spectral gain narrowing in quantum cascade lasers using terahertz time domain spectroscopy

Effect of transverse mode structure on the far field pattern of metal-metal terahertz quantum cascade lasers

Contact Info

Product

Resources

About