We introduce for the first time the novel idea of manipulating the momentum coupling coefficient using plasma confinement and shock wave reflection from the cavity walls. The plasma was confined using cylindrical geometries of various cavity aspect ratios to manipulate the momentum coupling coefficient (C m ). The Nd: YAG laser (532 nm, 5 ns pulse duration) was focused on the ferrite sample surface to produce plasma in a region surrounded by cylindrical cavity walls. The multiple reflections of the shockwaves from the cavity walls confined the laser-induced plasma to the central region of the cavity that subsequently resulted in a significant enhancement of the momentum coupling coefficient values. The plasma shielding effect has also been observed for particular values of laser fluencies and cavity aspect ratios. Compared with the direct ablation, the confined ablation provides an effective way to obtain high C m values.

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A laser can be used to propel distant objects. The ability of silicon to produce thrust and its propulsive parameters are needed to be studied in ablative laser propulsion (ALP). In this work, pure silicon and silicon doped with indium were subjected to ALP to achieve the momentum coupling coefficient and specific impulse to investigate its worth as a propellant. The experiment was conducted using the Nd:YAG laser (Quantel Brilliant) operating at fundamental harmonic (λ = 1064 nm and 5 ns pulse duration). In the given range of fluence, 1 × 105–5 × 105 J/m2, no significant difference among both samples for values of momentum coupling coefficient (Cm) and specific impulse (Isp) is observed; for instance, both propellants follow a decreasing trend for Cm. However, maximum enhancement for Cm and Isp is observed with a cavity aspect ratio of one. Cm and Isp are enhanced about 1.75 and 4.5 times, respectively, for pure silicon. The external cavity does not have any impact on Cm values for indium-doped silicon while values of Isp showed considerable enhancement.