  The novel method of observation and controlling of Bose-Einstein condensation
in the system of spatially and momentum-space indirect excitons in coupled
quantum wells using in-plane magnetic and normal electric fields is proposed.
Fields are used for exciton dispersion engeneering. In the presence of in-plane
magnetic field ground state of spatially indirect exciton becomes also indirect
in the momentum space. Manipulation of electric field magnitude is used for
tuning to resonance of transition of "dark" long-life spatially and
momentum-space indirect exciton in condensate into spatially and momentum-space
direct exciton in radiative zone, with phonon creation, and with subsequent
recombination of the direct exciton in radiative zone. Recombination rate of
indirect excitons in condensate according to proposed scheme sharply rises at
resonance. As a result besides enhanced spectral narrow photoluminescence
connected with recombination of direct exciton in radiative zone with specific
angular dependence, almost monochromatic and unidirectional beam of phonons
appears. An opportunity of obtaining of "phonon laser" radiation on the basis
of this effect in considered.
