Programmable fabrication of longitudinal spatial structures in a gas jet was achieved by using laser machining with a liquid-crystal spatial light modulator as the pattern mask. By this technique single-shot fabrication of arbitrary gas and/or plasma structures is demonstrated, which establishes the crucial step toward raising the designs and applications of high-field plasma devices to the level of adaptive feedback optimization.

By using deflectometry of a longitudinal probe pulse and reflective interferometry of a transverse probe pulse to resolve the spatiotemporal distribution of the preformed plasma, we characterize and control the plasma density distribution near the target surface for the development of solid-target x-ray lasers. We show that the use of prepulses in an ignitor-heater scheme can increase the scale length of the preformed plasma and how the effect varies with target materials. Many important issues crucial to x-ray lasing such as electron density distribution, electron temperature, and the optimal timing between pumping pulses can be resolved with these methods.

The effects of laser prepulse on splitting of a relativistically self-guided channel and suppression of Raman forward scattering instability in the propagation of an intense ultrashort laser pulse in an underdense plasma are studied. They are resolved by using probing interferometry, shadowgraphy, and spectrometry. By changing the prepulse intensity, the propagation of the laser beam can be controlled to show self-guiding or channel splitting. The effect of prepulse on Raman forward scattering instability shows that the instability is significantly reduced if the gas target is preionized, identifying ionization wakefield as the seeding mechanism for this process.

By utilizing the intensity- and duration-dependent heating and expansion rate of nanoplasma to generate a transient transverse gradient of the refractive index, prepulse controlled laser-beam propagation is demonstrated. The dynamical response of the macroscopic optical refractive index is traced back to the microscopic polarizability of nanoplasmas experimentally, in accordance with hydrodynamic nanoplasma models. In particular, the delay between the prepulse and the main pulse for maximum Rayleigh scattering is found to be longer than that for maximum x-ray emission, supporting the more refined one-dimensional self-consistent hydrodynamic nanoplasma model.

We discuss the design, construction, and output characteristics of a versatile 10-TW Ti : sapphire laser system of high stability and spatiotemporal quality. By pumping the three amplifier stages independently and running at saturation, an energy stability of 1.3% is obtained. Controls over self-phase modulation, high-order dispersion, spatial aberration, and amplified spontaneous emission are done by robust passive methods. A time–bandwidth product of 1.2 times the Fourier-transform limit with a temporal contrast larger than 5×108 in the -10-ns scale, 2×106 in the -100-ps scale, and 104 in the -1-ps scale are achieved. The beam can be focused down to 1.2 times the diffraction limit with 80% of the energy enclosed in the Gaussian focal spot. Beam-pointing stability is <13 μrad. Such high stability and spatiotemporal quality have made possible precision control over extremely nonlinear laser–plasma experiments, and the capability of computerized independent control of prepulse, pump pulse, probe pulse, and on-line diagnoses have made this system highly versatile and reliable.

Silicon oxide (SiOx) films grown by plasma-enhanced chemical-vapor deposition (PECVD) were investigated for applications in a course wavelength-division multiplexing (CWDM) network. The SiOx films were deposited on 4-in. silicon wafers based on the reaction of N2O/SiH4 precursors. After postdeposition annealing at 1,150°C, the transmission spectra of the films prepared at different flow rates of the precursor were compared. We found that the transmission spectrum of the films deposited at the low-flow conditions can be flattened to a ripple of less than 0.5 dB ranging from visible up to 1,470 nm. In addition, the material losses at wavelengths around 1,500 nm caused by absorption of Si-H and N-H bonds were significantly reduced.