Holographic assessment of self-phase modulation and blooming in a thermal medium

The use of a low-power laser beam to characterize self-phase modulation (SPM) and bubble formation during thermal blooming (TB), as well as manipulation of the bubbles, is reported. First, a low-power 633 nm laser beam is used to characterize the induced refractive index profile during SPM of a focused 514 nm pump beam in absorbing liquid media, e.g., a solution of red dye in isopropyl alcohol. The induced phase change is also characterized using digital holography via the 633 nm source as the probe and reference. During TB at higher pump powers, bubble formation occurs in the liquid. Using a modified setup, which minimizes the effects of gravity, buoyancy, and convection, stable bubbles are generated. These are characterized using in-line digital holography with the 633 nm probe beam. It is shown that the bubble size depends on exposure time of the pump and that the bubble can be steered by moving a focused low-power laser beam. Finally, possible applications of these thermally generated bubbles are discussed.