  We explore the semileptonic and nonleptonic decays of doubly heavy baryons
$(\Omega_{cc}^ {(*) +}, \Omega_{bb}^ {(*)0}, \Omega_{bc}^ {(*) -}, \Omega_{bc}^
{\prime 0}) $ induced by the $s\to u$ transition. Hadronic form factors are
parametrized by transition matrix elements and are calculated in the light
front quark model. With the form factors, we make use of helicity amplitudes
and analyze semileptonic and nonleptonic decay modes of doubly heavy baryons.
Benchmark results for partial decay widths, branching fractions,
forward-backward asymmetries and other phenomenological observables are
derived. We find that typical branching fractions for semileptonic decays into
$\ell\bar\nu$ are at the order $10^ {-7}-10^ {-8} $ and the ones for
nonleptonic decays are at the order $10^ {-5} $, which are likely detectable
such as in LHCb experiment. With the potential data accumulated in future, our
results may help to shape our understanding of the decay mechanism in the
presence of two heavy quarks.
