Fig. 1. Liquid microjet nozzle assembly composed of a $1/16$ inch Swagelok fitting, Vespel ferrule, $30~\unicode[STIX]{x03BC}\text{m}$ inner diameter glass capillary tube, and locking nut with affixed piezoelectric actuator for droplet formation.

Fig. 2. (A) Shadowgraphic microscope image of the liquid jet target. A $30~\unicode[STIX]{x03BC}\text{m}$ inner diameter capillary generates a $33~\unicode[STIX]{x03BC}\text{m}$ diameter jet. (B) False-color image of target presence probability. The color scale displays the probability that the target appears in the given location over the 1000 target exposures. Black indicates 100% probability that the target appears in the given location, while white illustrates a 0 probability. The sharp gradient between black and white, shown here, indicates the high positional stability of the liquid jet target.

Fig. 3. (A), (C) Shadowgraphic microscope images of primary and satellite droplet targets formed by manipulation of the piezoelectric actuator attached to the liquid jet nozzle. The primary droplet in (A) has a diameter of $55~\unicode[STIX]{x03BC}\text{m}$ and the satellite droplet in (C) has a diameter of $21~\unicode[STIX]{x03BC}\text{m}$. (B), (D) False-color images of the probability of target presence for primary and satellite droplet targets. Note that the large gradient, as compared to Figure 2(B), indicates a decrease in the dimensional and positional stability.

Fig. 4. (A) View of capillary nozzles and thin liquid sheet formed perpendicular to the plane of incidence between the jets. The full angle between the two jets is denoted as $\unicode[STIX]{x0394}\unicode[STIX]{x1D703}$. (B) View of the sheet formation within the jet plane of incidence. Note that the sheet is not aligned to this plane due to the grazing incidence of the two jets. (C) Top-down cross-section views of the jet intersection and resulting sheet formation. Section A–A illustrates the grazing incidence of the two jets which allows the formation of a submicron-thick sheet. Section B–B shows the relative angle, $\unicode[STIX]{x0394}\unicode[STIX]{x1D719}$ of the plane of the sheet with respect to the plane of incidence of the jets. The thick, cylindrical rim which supports the sheet is shown as well.

Fig. 5. (A) Microscope shadowgraphy image of the central region of the liquid sheet target in vacuum. (B) Spatially dependent thickness map across the liquid sheet, collected with a Filmetrics white-light interference profiler. The white cross indicates the location of the minimum sheet thickness at 450 nm. For scale, the width of the sheet in (B) is $560~\unicode[STIX]{x03BC}\text{m}$. This figure is reprinted with permission from Morrison et al.^[93].

Fig. 6. A variety of other unique target configurations can be created with droplets and jets. (A) Face-on view of droplet–droplet collision designed to make an isolated disk target. (B) Side view of the droplet–droplet isolated disk target shown in (A). (C) Droplet–jet collision generating a target with cylindrical surface shape. (D) Thin (${\approx}5~\unicode[STIX]{x03BC}\text{m}$ diameter) horizontal wire formed through the intersection of two jets while driving the Plateau–Rayleigh instability with a piezoelectric device.

Fig. 7. (A) Etalon reflectivity as a function of thickness for the given experimental conditions. The single-wavelength calculation is plotted with a solid line while the wavelength-broadened curve corresponding to a Gaussian FWHM bandwidth of 20 nm is given by the dashed curve. (B) The bandwidth-dependent etalon reflectivity is plotted on a semi-log scale for the third minima to illustrate the effect of incidence with a broad bandwidth laser pulse. Note that while the etalon calculation continues toward zero at the minima for the monochromatic case, the minimum reflectivity for a pulse with 20 nm bandwidth is approximately 0.1%.

Fig. 8. Experimental setup for measuring the thin, liquid sheet plasma mirror reflectivity. The laser was focused onto the liquid sheet at a $35^{\circ }$ angle of incidence. The reflected light was then scattered by a Spectralon panel, which was imaged by a CCD. While operating at a 1 kHz repetition rate, the vacuum chamber pressure was maintained below 1 millitorr.

Fig. 9. (A) Near-field mode of laser pulse input onto the plasma mirror. (B) Near-field mode of laser pulse after reflection from the plasma mirror. Note the smoothing of the mode performed by the plasma mirror.

Fig. 10. Schematic of vacuum and fluid containment system employed in this work. The syringe pump is fed by a liquid supply at atmospheric pressure. The supply line is capped with a $2~\unicode[STIX]{x03BC}\text{m}$ sintered steel filter to prevent debris from entering the system. $1/16$ inch Swagelok lines and fittings are used to route the fluid into the vacuum chamber, where the two nozzles generate the liquid sheet. A catcher and slide, designed to reduce gas backflow and splatter, direct the residual fluid to the liquid reservoir. Here the excess is isolated from the main vacuum chamber by a turbomolecular pump. The reservoir is kept at relatively low vacuum pressure (${\approx}100$  millitorr) through backing with a roughing line. Liquid from the reservoir can be recovered and reused in the system.

Fig. 11. Short-pulse (80 fs) shadowgraphic microscope images of the hydrodynamic evolution before and after irradiation with a high-intensity ($10^{18}~\text{W}/\text{cm}^{2}$) laser pulse for liquid (A)–(D) column, (E)–(H) droplet and (I)–(L) sheet targets. These images illustrate the modes of target deformation and prescribe feasible repetition rates for each type. (A) The liquid column begins as a continuous jet which is broken where the laser is incident, as shown in (B). (C) $10~\unicode[STIX]{x03BC}\text{s}$ after the laser arrives, the column is reestablished, while a conical sheet and droplet spray obscure the laser line of sight. (D) After $100~\unicode[STIX]{x03BC}\text{s}$ the droplet spray is cleared and a new column is set. (E) A continuous train of primary and satellite droplets are shown before the laser arrives. (F) Hydrodynamic explosion of the primary droplet destroys neighboring droplets within the series. In (G) and (H), separate primary droplets propagate into the appropriate position for subsequent laser shots after 48.1 and $83.9~\unicode[STIX]{x03BC}\text{s}$. (I) Two colliding liquid jets form a thin, flowing sheet. (J) $1~\unicode[STIX]{x03BC}\text{s}$ after the laser–target interaction a circular hole is vaporized. (K) After $10~\unicode[STIX]{x03BC}\text{s}$ liquid flow begins to reform the sheet and (L) at $24.9~\unicode[STIX]{x03BC}\text{s}$ the target surface is fully reformed.

Table 1. Pulse durations, Fourier-transform-limited bandwidth, and calculated minimum reflectivity for reflection from an etalon-like thin film at the first destructive minima.