Gain compression and abovethreshold linewidth enhancement. Importance of the microscopic effects on the linewidth. Such a breakup of the factors enables one to extract the. For the quantum dot qd lasers, the dynamical behaviors and modulation characteristics are signi. This provides an explanation for the wide range of values experimentally. Such findings are important for the design of a practical single broadband laser diode for applications in low coherence interferometry sensing and optical fiber communications. Using the injectionlocking technique, the above threshold alphafactor is measured to be as low as 0. The study uses a manybody theory with dephasing effects from carrier scattering treated. The model includes microscopically computed coulomb scattering rates. Submonolayer ingaasgaas quantumdot lasers with high. Dynamic properties of quantum dot distributed feedback lasers. Moloneyl 1 arizona center for mathematical sciences, university of arizona, tucson az 85721, usa 2 us.
Giant linewidth enhancement factor and purely frequency modulated emission from quantum dot laser b. Index termsgain compression, linewidth enhancement factor, quantum dot, semiconductor laser. The resonance frequency and eye diagram are presented. H factor and the fmtoam indices ratio fair in quantum dash dot semiconductor lasers. A narrowlinewidth external cavity quantum dot laser for. Osa linewidth enhancement factor in semiconductor lasers. The linewidth enhancement factor of qd lasers can be measured with several methods under different operation. This is in contrast to the case of a quantum well laser in which the linewidth enhancement factor is generally positive and the. Refractive index dynamics and linewidth enhancement factor. Dynamic properties of quantum dot distributed feedback. A quantum dot laser is a semiconductor laser that uses quantum dots as the active laser medium in its light emitting region.
Linewidth enhancement factor and chirp in quantum dot lasers jani oksanena and jukka tulkki department of electrical and communications engineering, helsinki university of technology, finland received 10 february 2003. As expected, a much lower lef is found than is common for interband lasers, but instead of the predicted value of zero, the lef. Clamping of the linewidth enhancement factor in narrow. Refractive index dynamics and linewidth enhancement factor in pdoped inasgaas quantumdot amplifiers citation for published version apa. H is an important parameter for semiconductor lasers. Submonolayer ingaasgaas quantumdot lasers with high modal gain and zerolinewidth enhancement factor zhangcheng xua the key lab of advanced technique and fabrication for weaklight nonlinear photonics materials, ministry of education, nankai university, tianjin 300071, p. Index terms linewidth enhancement factor, quantum dots, semiconductor laser. While spatial coherence is related to the beam divergence of the laser, spectral coherence is evaluated by measuring the.
Gain compression coefficient and abovethreshold linewidth. We focus on determining the ae spectrum of a typei qc laser with a lasing wavelength near 8. In particular, the feasibility of lasing at the gain peak with. Linewidth enhancement factor and chirp in quantum dot lasers. However subthreshold linewidth enhancement factor was measured taking values from 0. As the injection current increases, the gain rises superlinearly while changes in the index of refraction decrease. This work reports on the ultralow linewidth enhancement factor ahfactor of semiconductor quantum dot lasers epitaxially grown on silicon. We study a fivevariable electronhole model for a quantumdot qd laser subject to optical feedback. Combining theoretical and experimental studies show that optical injection strongly changes the behavior of the linewidth enhancement factor. Filamentation and linewidth enhancement factor in ingaas. Comparison of the carrier induced refractive index, gain, and linewidth enhancement factor in quantum dot and quantum well lasers a. Linewidth enhancement factor of terahertz quantum cascade.
In this work, the linewidth enhancement factor of a midinfrared quantum cascade laser emitting around 5. H factor of semiconductor quantum dot lasers epitaxially grown on silicon. Simulations of differential gain and linewidth enhancement. Gain compression coefficient and abovethreshold linewidth enhancement factor in inasgaas quantum dot dfb lasers h. Linewidth enhancement factor lef of inasinp quantum dot qd multiwavelength lasers mwls emitting around 1.
Introduction optical coherent sources with high modulation bandwidth and stable operation have attained great demands for optical communications. Lin, fourwave mixing analysis of quantum dot semiconductor lasers for linewidth enhancement factor extraction, opt. Lasers fabricated from such an active media exhibit device performance that is closer to gas lasers, and avoid some of the negative aspects of device. Linewidth enhancement factor and dynamical response of an. Semiconductor quantum dot lasers epitaxially grown on. Frequencydependent linewidth enhancement factor of optical injectionlocked quantum dotdash lasers cheng wang,1,2, mohamed e. Dynamics and spectral characteristics of quantum dot. Here, we propose and demonstrate a method for determining this parameter based on a direct measurement of variations in the laser gain and emission spectrum when subject to delayed optical feedback. Although this formula predicts the linewidth satisfactorily for gas lasers, it fails to predict the linewidth for semiconductor lasers. Refractive index dynamics and linewidth enhancement factor in p. Below the onset of gain saturation, the linewidth enhancement factor is as small as 0.
Pdf linewidth enhancement factor and chirp in quantum. Dynamic characteristics and linewidth enhancement factor. Calculation results show that the linewidth enhancement factor from the ground state of broadband qdot lasers. We have made a comparative study of the linewidth enhancement factor lef. Clamping of the linewidth enhancement factor in narrow quantumwell grinsch semiconductor lasers j. Submonolayer ingaasgaas quantumdot lasers with high modal gain and zero linewidth. Determining the linewidth enhancement factor via optical.
Quantum dot laser chip the semiconductor structure for the gain chip was grown by molecularbeam epitaxy. Laser linewidth is the spectral linewidth of a laser beam two of the most distinctive characteristics of laser emission are spatial coherence and spectral coherence. Pdf linewidth enhancement factor of quantumdot lasers. Importance of the microscopic effects on the linewidth enhancement factor of quantum cascade lasers tao liu,1 kenneth e. The quantum dot laser structures consist of seven layers of in0. Giant effective linewidth enhancement factors, close to 60, are measured on a quantum dot laser under specific biasing conditions. The linewidth of a laser is predicted by schawlowtownes formula 4. This work investigates the linewidth enhancement factor alphafactor and stability of an opticallyinjected inasingaas quantumdot fabryperot laser. Pdf this work reports on the ultralow linewidth enhancement factor ahfactor of semiconductor quantum dot lasers epitaxially grown on.
This paper describes an investigation of the linewidth enhancement factor. Gaas quantum dot active regions emitting in the nm band, and have compared the results both with those for quantum well devices operating at the same wavelength and with theoretical predictions. Comparison of the carrier induced refractive index, gain. Linewidth enhancement factor of inasinp quantum dot. The inasingaas dotsinawell dwell laser structure is grown by solid source molecular beam epitaxy on a 001. Es emission quantum dot qd laser under optical injection. The strong dependence of the linewidth enhancement factor on the photon density is explained by the enhancement. Measurement of the linewidth enhancement factor of. Linewidth broadening factor and gain compression in. Cthk1 linewidth enhancement factor of semiconductor. Recently, the linewidth enhancement factor of quantumwell vcsel with buried tunnel junction has been proposed 8.
Fourwave mixing analysis of quantum dot semiconductor. Gain, refractive index change, and linewidth enhancement factor of pdoped quantumdot lasers, ieee j. The linewidth enhancement factor is smaller in the qd laser and exhibits. Owing to the low density of threading dislocations and resultant high gain, an ah value of 0. Amplified spontaneous emission measurements are investigated below threshold in inas quantumdot lasers emitting at 1. Above the threshold, lefs at three different wavelengths around the gain peak of 1. The dynamic characteristics and linewidth enhancement. Air force phillips lab, kirtland afb, nm 87117, usa 3 permanent address.
Frequencydependent linewidth enhancement factor of. Abstractthis study explores the relative intensity noise characteristics of quantumdot verticalcavity surfaceemitting lasers qd vcsels. The minimum value of linewidth enhancement factor is about 3. Owing to the low density of threading dislocations and resultant high gain, an a h value of 0.
Gain and linewidth enhancement factor in inasquantumdot. Linewidth enhancement factor in inasgaas quantum dot lasers. Rp photonics encyclopedia linewidth enhancement factor. Moreover, the influence of the linewidth enhancement factor lef on the. Gain and linewidth enhancement factor in inas quantum dot. The linewidth enhancement factor lef of terahertz quantum cascade lasers is measured using an optical feedback selfmixing technique. We consider the case of a low linewidth enhancement factor and a short external cavity.
We present a multipopulation rate equation model for the analysis of the static and dynamic characteristics of a quantum dot qd semiconductor laser. Osa frequencydependent linewidth enhancement factor of. Results are presented for active region parameters and laser configurations important for minimizing. The linewidth enhancement factor ae plays an important role in determining the spectral linewidth of semiconductor lasers. Linewidth enhancement factor in semiconductor lasers subject to. Gain and linewidth enhancement factor in inas quantumdot laser. Pdf chapter 4 determination of linewidth enhancement. Above the laser threshold, the linewidth enhancement factor does not. Measurement of linewidth enhancement factor of different. Zilkie et al timeresolved linewidth enhancement factors in quantum dot and higherdimensional semiconductor amplifiers 1499 in a device can be attained if the factor can be broken down into values for each of these nonlinear processes 11. Linewidth enhancement factor of a typei quantumcascade. T ulkki, linewidth enhancement factor and chirp in quantum dot lasers, journal of applied physics 94, pp.
Linewidth enhancement factor an overview sciencedirect. Qcls are intrinsically narrowlinewidth sources, owing to a small linewidth enhancement factor lef as a result of their symmetric, or almost symmetric, gain curve. The model is applied to the extraction of the differential gain and linewidth enhancement factor of the qd laser simulating the same kind of experiments usually done in the laboratory. Moreover, the linewidth enhancement factor of qd fabryperot. We show that the various techniques commonly used to measure the linewidth enhancement factor can lead to different values when applied to quantum dot semiconductor lasers. In a real quantum dot laser the linewidth enhancement factor is nonzero because of manybody interactions5 and inhomogeneous broadening.
The factor 12 serves to convert the change of power gain. Introduction one property that distinguishes semiconductor lasers from most other laser systems is that there is a strong. This work reports on the ultralow linewidth enhancement factor a hfactor of semiconductor quantum dot lasers epitaxially grown on silicon. Due to the tight confinement of charge carriers in quantum dots, they exhibit an electronic structure similar to atoms.
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