R. Fedosejevs

Picosecond XeF amplified laser pulses

Picosecond third harmonic (353 nm) Nd : glass laser pulses have been amplified by factors of ≳6 000 in a high‐pressure XeF discharge. Peak powers ∼50 kW have been observed.

Generation of single synchronizable picosecond 1.06‐μm pulses

We report the generation of reliable synchronizable single mode‐locked l.06‐μm pulses with pulsewidths variable from 1.3 ns to the spectral transform limit of 15 ps.

Actively mode-locked and Q-controlled Nd:glass laser.

A Q-controlled Nd:glass ring laser system has been developed which is actively mode-locked by means of either KD *P or LiNbO(3) electro-optic modulators and is capable of producing 1.5 mJ, 100 ps, 1.06 mum pulses synchronized to better than 400 ps to an external event. By using prelase methods or saturable absorbers shorter pulses from 37 to 15 ps duration can be generated with poorer synchronization.

Picosecond gain and saturation measurements of the 353‐nm XeF laser line

The spectral characteristics, temporal gain profile, and saturation energy have been measured for the 353‐nm XeF laser line using a picosecond probe pulse of the third harmonic of a Nd : glass laser.

Synchronizable actively mode‐locked Nd:glass laser

With the development of an actively mode‐locked Nd:glass laser incorporating dynamic Q control, a single subnanosecond 1.06‐μ pulse has been synchronized to a 1‐ns‐duration 10.6‐μ CO2 laser pulse to within <400 ps.

Unidirectional travelling wave operation of a mode-locking Nd:Glass ring laser

Abstract The development of unidirectional mode-locked pulses in a Nd:glass ring laser is studied for various combinations of active and passive mode-locking and pulse direction discrimination elements.

The electron density structure of the plasma produced on glass microballoons by 10.6 μm radiation

A detailed study is presented of the 0.4–40 nc plasma region created by nanosecond, 10.6 mm, 1–38 J laser pulses incident upon unfilled glass microballoon targets. Many interesting features were observed including electron density scale lengths (Lc) and step heights (Np) through nc as short as 0.3l0 and as high as 38nc, respectively. An attempt has been made to explain these parameters in terms of recent theories, and a consistent picture only seems to emerge if important roles are assigned to the superthermal plasma component and the effect of inhibited energy transport during laser irradiation.

Observations consistent with self‐generated magnetic fields in CO2 laser‐produced plasmas

The spatial structure of extreme ultraviolet (XUV) line emission from plasmas produced by nanosecond CO2 laser pulses has been examined with a slitless normal‐incidence vacuum‐ultraviolet spectrograph in the 200–500‐A spectral region. The anomalous structural behavior of these spectra is consistent with the existence of self‐generated magnetic fields. These fields could also explain the gross plasma structure observed through picosecond interferometry.

Picosecond Interferomatric Studies of CO2 Laser Produced Plasmas

It has recently become apparent that the interaction of intense, shortpulse, CO2 laser radiation with matter is dominated by collisionless absorption processes which couple energy primarily into fast electrons. This quickly leads to the formation of a two component plasma system with a relatively long lifetime, high density, thermal plasma adjacent to the solid target, surrounded by a much more transient collisionless superthermal plasma which rapidly propagates out of the interaction region. The diagnosis of these two regimes with high spatial and temporal resolution can provide considerable insight into the interaction physics relevant to current laser fusion studies.

Picosecond Diagnosis of CO2 Laser Produced Plasmas

The investigation of the interaction of intense 10 μm laser radiation with solid targets has in the past few years acquired increased significance due to the potential application of CO2 lasers towards the achievement of laser fusion. In parallel to this effort, similar investigations are underway utilising 1μm radiation from high power Nd: glass lasers. Although in many respects the stringent experimental demands on plasma and laser diagnosis are similar in both investigations, the difference in operating wavelength range has forced the development of alternative approaches toward the achievement of these aims. This has become particularly evident in those areas involving ultrafast diagnosis of the laser pulse characteristics and in the characterisation of the plasma by fast optical analysis. Whereas in the near IR and visible region the relative abundance of available sensitive ultrafast detectors and techniques has permitted accurate laser beam characterisation, comparable diagnosis in the CO2 laser range has presented many challenging problems, which apparently will only be overcome by the adoption of novel techniques. In this paper, we wish to describe some of the approaches we have adopted to provide picosecond optical diagnostics in an investigation of the interaction of intense (>1014W cm-2) short (∿l ns) CO2 laser pulses with solid targets.