A high energy, high repetition rate workpiece surface heating method and apparatus are disclosed which may comprise a pulsed XeF laser operating operating at or above 4000 Hz and producing a laser output light pulse beam at a center wavelength of about 351 nm; an optical system narrowing the laser output light pulse beam to less than 20 µm in a short axis of the laser output light pulse beam and expanding the laser output light pulse beam to form in a long axis of the beam workpiece covering extent of the long axis; the optical system including a field stop intermediate the laser and the workpiece; the workpiece comprising a layer to be heated; wherein the optical system focuses the laser output light pulse beam at a field stop with a magnification sufficient to maintain an intensity profile that has sufficiently steep side walls to allow the field stop to maintain a sufficiently steep beam profile at the workpiece without blocking the beam profile at too high an intensity level 2. The apparatus may also have a high average power in the laser output light pulse beam as delivered to the workpiece and a linebow correction mechanism in a short axis optical assembly. The linebow correction mechanism may comprise a plurality of weak cross cylinders. The system may comprise a catadioptric projection system. The line width due to laser diffraction and divergence may be less than geometric limitations. The system may project adjacent peaks of the nominal XeF spectrum to improve overall depth of focus through the separate center wavelengths of each respective adjacent peak having a different focal plane at the workpiece. The system may comprise a linebow is correction mechanism within a field stop optical assembly correcting linebow at the field stop plane and within a workpiece projection optical assembly correcting linebow at the workpiece plane.

Laser thin film poly-silicon annealing optical system

A laser crystallization apparatus and method are disclosed for selectively melting a film such as amorphous silicon that is deposited on a substrate The apparatus may comprise an optical system for producing stretched laser pulses for use in melting the film In still another aspect of an embodiment of the present invention, a system and method are provided for stretching a laser pulse In another aspect, a system is provided for maintaining a divergence of a pulsed laser beam (stretched or non-stretched) at a location along a beam path within a predetermined range In another aspect, a system may be provided for maintaining the energy density at a film within a predetermined range during an interaction of the film with a shaped line beam

Systems and methods for implementing an interaction between a laser shaped as a line beam and a film deposited on a substrate

We demonstrate intracavity degenerate four-wave mixing in the saturable gain medium of a dye laser. The dye laser is a synchronously pumped bidirectional ring laser that produces pulses of 4 ps duration. The dynamics of the interaction provides information on the phase coherence of the pulses. A simple theory of transient degenerate four-wave mixing is presented that accurately describes the measurements.

Degenerate four-wave mixing of picosecond pulses in the saturable amplification of a dye laser

High-reflectivity four-wave mixing by gain saturation in a Nd:YAG laser amplifier is demonstrated. With a four-pass geometry, the phase-conjugate reflectivity of a Q-switched pulse (18-ns duration) is ∼2500, and for a long pulse (relaxation oscillation duration ∼100 μs) it is ∼30. Temporal and energy characteristics of the conjugate beam are presented. A phase-conjugate Nd:YAG TEM00 laser resonator is also produced in which the Nd:YAG rod is simultaneously the laser gain medium and the phase-conjugating device.

High-reflectivity four-wave mixing by gain saturation of nanosecond and microsecond radiation in Nd:YAG.

Degenerate four-wave mixing with orthogonally polarized pump beams at /spl lambda/=106 /spl mu/m in the saturable gain of a flash-lamp-pumped Nd:YAG amplifier is investigated, both experimentally and theoretically, using pulses of duration much less than the population relaxation time We introduce a new set of coupled-wave equations in this short pulse regime that includes the effect of the four interacting waves and the laser gain experienced by all the beams The dependence of the efficiency of the process on the small-intensity-gain-length product, beam ratios, and fluences is analyzed A reflectivity of a weak probe beam of 25 percent and a transmission-gain-grating diffraction efficiency of 32 percent are achieved Finally, the temporal shape of the conjugate signal is studied for various gain-saturation regimes >

Transient analysis of degenerate four-wave mixing with orthogonally polarized pump beams in a saturable Nd:YAG amplifier

We have studied phase conjugation by degenerate frequency mixing in saturable amplifiers for various interaction geometries and polarization combinations. Theoretical results are compared with measurements in a XeCl amplifier. Experimental reflectivities as high as 100 are observed.

/pdf/degenerate-frequency-mixing-in-saturable-amplifiers-4u5v0pyhzq.pdf

Degenerate frequency mixing in saturable amplifiers

The use of a laser amplifier as a Degenerate Four‐Wave Mixing (DFWM) element for phase conjugation is a powerful general technique, particularly useful for UV excimer lasers In this paper we will discuss our initial experiments, which yielded the first demonstration of DFWM in a XeCl amplifier

B. L. Wexler

Papers

Degenerate frequency mixing in saturable amplifiers

Use of XeCl amplifiers for degenerate four‐wave mixing