Role of physical parameters on the photorefractive performance of semiconductor multiple quantum wells

Asymmetric Directional Coupler Controlled by Photorefractive Grating

“…As an example a coupler with a guiding slab consisting of GaAs/AlGaAs multiple quantum well (MQW) layer with planes parallel to the K vector of the grating was considered. The MQW structure, in accordance with previous studies [8,9] is simulated by a strongly anisotropic homogeneous semiconductor with the parallel mobilities of the carriers much higher than the perpendicular ones. Parameters of the system are listed in Table. We used the effective index method TABLE Parameters used in this paper for GaAs/Al0.3Ga0.7As MQW layer.…”

“…The resulting space-charge electric field cause the change of the refractive index through the electrooptic effect. Such model leads to the following equations based on a classical Kukhtarev-Vinetskii model [8]: Fig. 3.…”

Multiple Quantum Well Directional Coupler with Photorefractive Grating

“…The MQW structure , i n accorda nce wi th previ o us studi es [8,9] was simul ated by a stro ngl y ani sotro pi c ho mog eneous semi conducto r wi th the para l l el m obi l iti es of the carri ers much hi gher tha n the p erp endi cul ar ones. An e£ cient op erati on of the coupl er i s p ossibl e wi th hi gh f requency externa l wa ves wri ti ng the gra ti ng and l ower f requency gui ded mo des rea di ng it.…”

“…The resulti ng space-charge el ectri c Ùeld causes the change of the refra cti ve i ndex due to the electro -opti c e˜ect. Assum i ng tha t the pl anes of MQW are perp endi cul ar to the x -axi s and the electri c Ùeld i s appl i ed al ong the z -axi s the fol l owi ng equati ons ba sed on a classical Kukhta rev{ Vi netski i m odel [8] can b e deri ved: The symb ols i n the ab o ve equati ons are: n e | the free electro n and n h | the free ho l e concentra ti ons, N D | dono rs, N + D | i oni sed dono rs and N A | accepto rs concentra ti ons, j e | the electro ni c and j h | the hol e current densiti es, E | the to ta l electri c Ùeld (E = E 0 + E sc, where E sc i s a space-charge Ùel d and E 0 i s an externa l Ùel d), I | the l i ght intensi ty , Ûe and Ûh | the consta nts descri bi ng recombi nati on of electro ns and hol es, ñ e | electro n and ñ h | ho l e mobi l iti es al ong the qua ntum wel l s, " 0 | the perm i tti vi ty o f the vacuum , " | the e˜ecti ve di electri c consta nt of MQW structure, e | the absol ute val ue of the elementa ry charg e, k B | the Bo l t zm ann consta nt a nd T | the absol ute tem p erature. Therm al exci ta ti on of the carri ers and tra nsverse carri er m obi li ty are no t i ncl uded i n the ab o ve set of equati ons.…”

“…The am pl i tudes of the exp onenti al facto rs can ha ve real and i magi nary parts so tha t the sol uti ons may ha ve an arbi tra ry pha se shi fts com pa ri ng wi th the i ntensi ty pa ttern. Acco rdi ng to [8] the space-charg e Ùeld i n a steady sta te f or Û e = Û h = Û i s of the form…”