CALCULATION OF DELTA-N(2) AND KAPPA FOR AN ACOUSTICALLY INDUCED DISTRIBUTED-BRAGG-REFLECTOR (ADBR)

The preliminary feasibility analysis and theoretical design of an acou stically induced distributed Bragg reflector (ADBR) suitable for possi ble integration with a III-V semiconductor laser is presented, The pro posed ADBR structure consists of a simple unapodized interdigitated tr ansducer (IDT) patterned by e-beam lithography atop a III-V compound s emiconductor optical waveguide structure, It is proposed that a gigahe rtz-range surface acoustic wave (SAW) could present a tunable distribu ted Bragg reflector (DBR) index grating to a colinearly propagating gu ided optical wave, Both the change in the impermeability tensor, Delta n(2), and the resulting distributed feedback (DFB) coupling coefficie nt, kappa, in the ADBR section are calculated due to only the classic photoelastic effect by employing a Laguerre polynomial SAW analysis te chnique, The SAW fields are normalized using the normal mode IDT equiv alent circuit model and a power balance technique to provide realistic kappa values in order to assess the feasibility of this device while driven at its center frequency, The analysis of the ADBR kappa is limi ted to the coupling between counterpropagating TE optical modes and is calculated using general overlap integral expression, For an example lambda(o), = 1.55 mu m In1-xGaxAsyP1-y-InP multiple-quantum-well (MQW) laser structure coated with a 0.1-mu m ZnO piezoelectric layer, the m aximum ADBR re was calculated to be 4.9 cm(-1) when using a series-ind uctor-tuned submicron electrode IDT-SAW reflector configuration driven by a RF source operating at approximately 2.9 GHz. It is shown that e xceeding the maximum strain on the substrate or the occurrence of diel ectric breakdown can put an upper limit on the realizable value of kap pa. The potential optical tunability of an ADBR section is estimated f or the case when an unapodized IDT is used for SAW generation, Finally , various fabrication and design techniques are listed which may enhan ce the ADBR kappa value, along with a list of other physical effects w hich may need to be considered in future analyses.