  Nonlinear optical processes are vital for fields including
telecommunications, signal processing, data storage, spectroscopy, sensing, and
imaging. As an independent research area, nonlinear optics began with the
invention of the laser, because practical sources of intense light needed to
generate optical nonlinearities were not previously available. However the high
power requirements of many nonlinear optical systems limit their use,
especially in portable or medical applications, and so there is a push to
develop new materials and resonant structures capable of producing nonlinear
optical phenomena with low-power light emitted by inexpensive and compact
sources. Acoustic nonlinearities, especially giant acoustic nonlinear phenomena
in gas bubbles and liquid droplets, are much stronger than their optical
counterparts. Here, we suggest employing acoustic nonlinearities to generate
new optical frequencies, thereby effectively reproducing nonlinear optical
processes without the need for laser light. We critically survey the current
literature dedicated to the interaction of light with nonlinear acoustic waves
and highly-nonlinear oscillations of gas bubbles and liquid droplets. We show
that the conversion of acoustic nonlinearities into optical signals is possible
with low-cost incoherent light sources such as light-emitting diodes, which
would usher new classes of low-power photonic devices that are more affordable
for remote communities and developing nations, or where there are demanding
requirements on size, weight and power.
