Lumonics Inc.

John W Montgomery

Ian J Miller

Robert G Parker

Philip D Barton

Pierre Langlois

The cooling of the outer surface of the rod or other solid active element of a solid state laser is improved by causing coolant to travel in a plurality of, preferably streamline, helical flows extending around this surface in contact with it. The respective longitudinal components of a pair of the helical flows preferably extend in opposite directions along the surface to improve the uniformity of cooling.

Laser cooling

Laser marking systems (60, 80, 160, 250) having increased part throughput are obtained by disposing diffractive optics (70, 70A, 94, 170, 252) across a primary laser beam. Preferred diffractive optics for high power marking lasers are defined in optical materials with discrete surface levels.

Laser system for simultaneously marking multiple parts

For separation of second and higher order second harmonics from a composite laser beam, a substrate is provided with a binary level relief structure that, in the preferred construction, consists of a regular series of parallel substantially rectangular grooves on one or both of its major surfaces. In a transmissive grating, which is traversed only once by the beam, the depth h of the grooves is chosen to be .lambda. divided by n.sub.1 -n.sub.0, where n.sub.0 is the refractive index external to the grating (assumed to be approximately unity for air), n.sub.1 is the refractive index of the substrate, and .lambda. is the wavelength that will pass directly through the grating, e.g. the second harmonic. Wavelengths greater than .lambda., e.g. the fundamental 2.lambda., will be diffracted away from the beam path. When a reflective coating is applied on the surface with the relief structure, the groove depth is chosen to be .lambda. divided by 2n.sub.0 or 2n.sub.1 depending upon whether the beam encounters the relief structure from outside the substrate or from inside, respectively. A more general formula for the value of h provides for the incident beam arriving at an inclination to the normal to the substrate surface. Also the relief structure itself can be more general in nature, consisting of elevated and unelevated portions of various shapes.

Laser beam frequency doubling system

To maintain substantially constant the temperature of a diode junction of a pulsed, cooled, diode laser and hence the wavelength of the optical output of the laser, which laser is used for optically pumping a main, pulsed, solid state laser, the diode junction is heated by an external source during inactive intervals between pulses of the diode laser. This heating, which preferably is achieved by passing a heating current through the diode junction, is adjusted to ensure that, per a unit time greater than the length of an inactive interval, the heat energy received by the diode junction from this external heating together with the heat energy generated in the diode junction itself by the pulses is substantially constant independent of the length of the inactive intervals. Preferably the heating current has a constant level except for a period after each pulse when the level is reduced, e.g. to zero. To achieve the constant total heating of the diode junction, this period has a length such that the heat energy denied to the diode junction during this period is substantially equal to the heat energy generated in the diode junction during a pulse. The arrangement permits variation of the pulse repetition rate of the main laser at will without adverse effect on its pumping by the diode laser.

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Stittsville, Canada

John W Montgomery