Coherent light generators – Particular resonant cavity – Mirror support or alignment structure
Reexamination Certificate
2002-03-28
2003-04-29
Ip, Paul (Department: 2828)
Coherent light generators
Particular resonant cavity
Mirror support or alignment structure
C372S054000, C372S109000, C372S108000, C372S021000, C372S050121
Reexamination Certificate
active
06556614
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention generally relates to optically pumped, solid-state, q-switched and linearly polarized laser cavity assemblies and, more specifically, to a method of making these non-pump elements in one piece that can produce pulse energies of 1-1000 millijoules for range-finders.
2. Description of Prior Art
Many military and commercial applications require high power optical pulses and normally employ lasers consisting of cavity assemblies surrounded by energetic Xenon, pyrotechnic or similar types of flash lamps or a diode lasers that provide the necessary pump power. Each cavity assembly; which includes all laser elements except the optical pump; is typically made up of at least four discrete elements. The first element is a rod, many times longer than its diameter of nonconductive crystalline gain material that lases at a characteristic wavelength when exposed to the light pump. The rod normally has a uniform regular cross-section and a longitudinal optical axis centered in that cross-section. The ends of the rod are ground and polished normal to this axis. The second element is usually a perfectly flat highly reflective (HR) mirror, at least for the lasing wavelength, mounted precisely normal to the rod axis and spaced slightly from a first end of the rod. The third element is an output coupler or (OC) mirror which, though also highly reflective, has a specified percent transmission (leakage), at the lasing or output wavelength. The third element is mounted similar to the second near the opposite or output end of the rod. The fourth element, an optional passive q-switch, is a wafer of material with flat and parallel broad faces centered on the optical axis of the rod between the second and third elements and parallel to them. The passive q-switch reduces the Q of the high Q cavity defined by the other three elements, until the inverted population of energy quanta in the rod reaches a critical level. The wafer then automatically restores the high Q to generate a short high power pulse. The rod of gain material is usually a well known laser crystal, such as Neodymium:Yttrium-Aluminum-Garnet (Nd:YAG), ruby, etc. These laser crystals absorb the pump wavelength and fluoresce at the lasing wavelengths. The assembly will lase without the q-switch, but does not emit sufficient peak power for range finders and similar applications. The q-switch concentrates the output photons in time spaced pulses that have peak powers several orders of magnitude greater than output that is not Q-switched. The passive q-switch can be a wafer of impregnated plastic or other materials. Additional elements may include anti-reflection coatings, a polarization device and an optical parametric oscillator to change the output frequency. In prior art embodiments the purpose of using adjustable spaced elements has been to compensate for their imperfect shape and/or placement. The disadvantage of these assemblies lies in the large number of elements required and the need for numerous adjustable support members that permit precise mechanical alignment of the various optical components. These support members make manufacturing and repair of the assemblies very complicated and expensive.
A goal of the present invention is to reduce the number of parts in the cavity assembly to two active optical elements and finally to a single structure by adding a novel base pallet. An assembly using an optical parametric oscillator is not part of this disclosure, but is covered in applicants' co-pending application mentioned above. A simpler structure using only one laser rod is described in applicants' copending application (NVL-3213) entitled “PSEUDO-MONOLITHIC Q-SWITCHED LASER WITH A BREWSTER NOTCH POLARIZER”.
SUMMARY OF THE INVENTION
A photon pumped laser cavity assembly consisting of a pair of coaxial rods made from laser gain material with precisely cut side-faces and end-faces. Some of the end-faces are covered by at least one of a dielectric or metal coating highly reflective to the laser output beam, a wafer of polarizing material, and a dielectric or metal coating partially reflective to the laser beam. In one configuration the rods may each have one of a pair of uncovered parallel closely opposed polarizing end-faces oriented at the Brewster angle to the common optical axis of the rods. In all configurations the rods are mounted on a pallet or substrate that maintains their orientation and position.
REFERENCES:
patent: 4731795 (1988-03-01), Clark et al.
patent: 5854802 (1998-12-01), Jin et al.
Barr Dallas N.
Nettleton John E.
Schilling Bradley W.
Holford John E.
Ip Paul
Lee Milton W.
Rodriguez Armando
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