Asymmetric double-quantum-well phase modulator using surface acoustic waves

Choy, Wallace C. H.; Li, E.H.; Weiss, B.L.

doi:10.1109/3.720217

Cited by 9 publications

(4 citation statements)

References 19 publications

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“…Once the quantum confinement structures and the material compositions are determined, the emission peak can be confirmed. For dynamic methods, external electric field (see, for example, [18,19]), acoustic wave [20], and temperature [21,22] can be used to tune the transition energy. By reducing the temperature from 283 K to 4:2 K, the dominated peak of the conventional ZnSe photoluminescence (PL) blueshifts for about 100 meV from ∼2:7 to ∼2:8 eV [21,22].…”

Section: Introductionmentioning

confidence: 99%

Largely extended light-emission shift of ZnSe nanostructures with temperature

Choy¹,

Leung²

2011

Appl. Opt.

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ZnSe nanowires and nanobelts with zinc blende structure have been synthesized. The morphology and the growth mechanisms of the ZnSe nanostructures will be discussed. From the photoluminescence (PL) of the ZnSe nanostructures, it is interesting to note that red color emission with only a single peak at the photon energy of 2 eV at room temperature is obtained while the typical bandgap transition energy of ZnSe is 2:7 eV. When the temperature is reduced to 150 K, the peak wavelength shifts to 2:3 eV with yellowish emission and then blue emission with the peak at 2:7 eV at temperature less than 50 K. The overall wavelength shift of 700 meV is obtained as compared to the conventional ZnSe of about 100 meV (i.e., sevenfold extension). The ZnSe nanostructures with enhanced wavelength shift can potentially function as visible light temperature-indicator. The color change from red to yellowish and then to blue is large enough for the nanostructures to be used for temperature-sensing applications. The details of PL spectra of ZnSe at various temperatures are studied from (i) the spectral profile, (ii) the half-width half-maximum, and (iii) the peak photon energy of each of the emission centers. The results show that the simplified configuration coordinate model can be used to describe the emission spectra, and the frequency of the local vibrational mode of the emission centers is determined.

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Section: Introductionmentioning

confidence: 99%

Largely extended light-emission shift of ZnSe nanostructures with temperature

Choy¹,

Leung²

2011

Appl. Opt.

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“…The absorption change of 3600 cm Ϫ1 can be obtained although the loss is large ͑2200 cm Ϫ1 ͒. It should be noted that in order to obtain a large absorption change or refractive index change for use in optical modulators, asymmetric DQW should be used, 8,9 although the optimization of asymmetric DQW for optical modulators is not the subject of the work presented here.…”

Section: Effects Of Applied Electric Fieldsmentioning

confidence: 99%

“…Currently, coupling effects in double quantum wells ͑DQWs͒ for use in optical devices have been of considerable interest. By optimizing the DQW structure, the coupling effects can provide a large blueshift of the transition energy, 7 a large refractive index change, 8 an enhanced absorption change, 9 or a strong gain switching 10 as with the quantum confined Stark effect. However, for the InGaAs/InAlAs DQW structure, there are only a few reports on its optical properties 11 and the modeling has not taken into account the band mixing effect of valence subbands and the coupling effect of excitons, which will have significant effects on the QW optical properties.…”

Section: Introductionmentioning

confidence: 99%

Optical properties of InGaAs/InAIAs diffused double quantum wells

Choy

2000

Journal of Applied Physics

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The effects of interdiffusion on the subbands and optical properties of InGaAs/InAIAs double quantum well ͑QW͒ have been theoretically studied. The results show that since a double QW ͑DQW͒ can be diffused to become an effectively single QW structure, the characteristic features in the subbands structure and optical properties of a strongly coupled DQW structure and that of a single QW structure can be obtained by a suitable annealing time. Moreover, the increase in separation between the first symmetric and antisymmetric heavy hole subbands and the increase in the spin splitting of the valence subbands of the diffused DQW, due to an applied electric field, diminish when annealing time increases. In optimizing the In 0.53 ͑Al a Ga 1Ϫa) 0.47 As/In 0.52 Al 0.48 As DQW structure, the results show that symmetric DQW with no Al content in wells can provide large material gain and radiative spontaneous recombination rate. With interdiffusion, the material gain and recombination rate reduce but the reduction saturates when the DQW structure is diffused to effectively become a single graded QW. By subjecting the DQW and an as-grown single QW to the same annealing conditions ͑where the summation of the width of the two wells and the separation barrier of the DQW equals the well width of the single QW͒, the diffused DQW can provide a larger material gain and radiative recombination rate than the diffused single QW when the annealing time is short. Therefore, the short-time diffused DQW is more useful for laser applications. Besides, since Al diffuses into the wells, the transition energy of the QW structure increases so that the operating wavelength of the optical devices can be adjusted.

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“…Double quantum wells (DQWs) have attracted attention due to their potential applications in low threshold lasers, [1,2] photoswitches, [3] and phase modulators [4] since last two decades. Compared with symmetric DQWs, the carrier levels and distribution in asymmetric double quantum wells (ADQWs) [3] are more complex due to the asymmetric quantum confinement.…”

Section: Introductionmentioning

confidence: 99%

Exciton optical absorption in asymmetric ZnO/ZnMgO double quantum wells with mixed phases*

et al. 2020

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The optical absorption of exciton interstate transition in Zn1 − xl Mg xl O/ZnO/Zn1 − xc Mg xc O/ZnO/Zn1 − xr Mg xr O asymmetric double quantum wells (ADQWs) with mixed phases of zinc-blende and wurtzite in Zn1 − x Mg x O for 0.37 < x < 0.62 is discussed. The mixed phases are taken into account by our weight model of fitting. The states of excitons are obtained by a finite difference method and a variational procedure in consideration of built-in electric fields (BEFs) and the Hartree potential. The optical absorption coefficients (OACs) of exciton interstate transition are obtained by the density matrix method. The results show that Hartree potential bends the conduction and valence bands, whereas a BEF tilts the bands and the combined effect enforces electrons and holes to approach the opposite interfaces to decrease the Coulomb interaction effects between electrons and holes. Furthermore, the OACs indicate a transformation between direct and indirect excitons in zinc-blende ADQWs due to the quantum confinement effects. There are two kinds of peaks corresponding to wurtzite and zinc-blende structures respectively, and the OACs merge together under some special conditions. The computed result of exciton interband emission energy agrees well with a previous experiment. Our conclusions are helpful for further relative theoretical studies, experiments, and design of devices consisting of these quantum well structures.

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Asymmetric double-quantum-well phase modulator using surface acoustic waves

Cited by 9 publications

References 19 publications

Largely extended light-emission shift of ZnSe nanostructures with temperature

Largely extended light-emission shift of ZnSe nanostructures with temperature

Optical properties of InGaAs/InAIAs diffused double quantum wells

Exciton optical absorption in asymmetric ZnO/ZnMgO double quantum wells with mixed phases*

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