Classifications

• • H—ELECTRICITY
  • H01—ELECTRIC ELEMENTS
  • H01S—DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL
  • H01S3/00—Lasers, i.e. devices using stimulated emission of electromagnetic radiation in the infrared, visible or ultraviolet wave range
  • H01S3/02—Constructional details
  • H01S3/03—Constructional details of gas laser discharge tubes
  • H01S3/0315—Waveguide lasers

Definitions

• the present invention relates generally lasers. More specificallv, the invention relates to rectangular cross-sectional waveguide laser havi improved performance.
• the squa cross-sectional waveguide laser comprises a pair spaced apart and parallel ceramic dielectric walls which a pair of spaced apart and parallel met electrodes are secured to define a waveguide cavitv square cross section.
• the metal electrodes, forming two the waveguide laser walls are comparativelv good he conductors, there is still a practical limit to t amount of heat which can be dissipated through the walls.
• the conventional waveguide laser has a limit to its usable power output.
• Conventional waveguide lasers contain the gaseous lasing medium under pressure.
• the pressure of the gas has a relationship upon the maximum output frequency tuning range of the laser.
• Generallv the higher the pressure, the higher the lasing frequenr.v tuning range.
• the excitation voltage must be increased in order to form a plasma in the laser waveguide cavity. If the voltage is increased too much, arcing can occur with damaging consequences.
• conventional waveguide lasers also have a practical limit to the upper output frequency tuning range.
• gas molecules can have several vibrational states, each corresponding to a different spectral line or output frequency.
• the lines may be close to one another r the production of more than one line can be problematic for certain sensitive applications.
• One technique for handling this problem is to place a grating in the laser beam path.
• the grating has a plurality of etched parallel grooves which selectively pass one of the lines or frequencies while reiecting or attenuating the others. In this fashion, a true monochromatic output beam is produced.
• the present invention greatly improves upo conventional waveguide lasers.
• r a/b
• Among the advantages of th waveguide laser of the invention are better cooling better spectral line resolution, lower voltag requirements, higher power output, higher frequenc tuning range and lower probability of arcing damage.
• Th waveguide laser design is well-suited for RF pumpe waveguide lasers.
• the waveguid laser comprises first and second parallel sidewalls an third and fourth parallel sidewalls connected to define waveguide cavity.
• a lasin medium such as a pressurized gas including anv of th gases selected from the group consisting of CO-,, CO, N-, He, Xe and mixtures thereof.
• a means is provided on a least one of the sidewalls for introducing energy int the waveguide cavity to cause the medium to lase.
• Th first and second sidewalls are orthogonal to the thir and fourth sidewalls and the first and second sidewall are longer than the third, and fourth sidewalls, such tha the waveguide cavity is rectangular in cross section.
• the first and second sidewalls comprise electricall conductive electrodes while the third and fourt sidewalls comprise a dielectric material such as BeO, o 1 2 0 3 .
• the lasin medium is selected from the group consisting of CO_, CO N 2 , He, Xe and mixtures thereof. If desired, diffraction grating can be placed in the waveguide cavit in order to select a desired spectral line.
• the metho further comprises exposing at least one of the meta electrodes to a heat removal medium for cooling th lasing medium.
• FIG. 1 is a cross-sectional perspective view o the waveguide laser of the invention
• FIG. 2 is a graph depicting the effect of th aspect ratio r on the small signal gain of the laser o FIG. 1.
• the curves depict the gain as a function position x for different aspect ratios r under t following parameters:
• Wavegui laser 10 comprises first and second parallel sidewalls and 14 which comprise metal electrodes.
• the wavegui laser further includes third and fourth sidewalls 16 a 18 which are comprised of dielectric material 20, such BeO. Attached to the first sidewall electrode 12 is electrically conductive RF feed through conductor 2 Conductor 22 is connected to a source of RF energy f pumping energv into the laser.
• Sidewalls 12-18 define laser cavitv 24 whi extends longitudinally as illustrated.
• Sidewalls 12 a 14 are orthogonal to sidewalls 16 and 18 and sidewalls and 14 are longer than sidewalls 16 and 18, there defining a rectangular cross section.
• Cartesian coordinate svstem xyz
• FIG. 1 illustrating the orthogonality of the sidewall
• sidewalls 12 and 14 are parallel to the dimension
• sidewalls 16 and 18 are parallel to the dimension
• the waveguide extends longitudinally i the z direction.
• the rectangular cross section of the waveguid laser may be defined in terms of the aspect ratio r - a/b, where a is the distance from the center of th waveguide cavity to either sidewall 16 or 18 and b is th distance from the center of the waveguide cavitv t either sidewall 12 or 14.
• a is the distance from the center of th waveguide cavity to either sidewall 16 or 18
• b is th distance from the center of the waveguide cavitv t either sidewall 12 or 14.
• sidewalls 16 and 18 ar spaced apart a distance 2a while metal electrod sidewalls 12 and 14 are spaced apart a distance 2b
• the aspect ratio r is in the range from abou 0.20 to 0.5 *
• the laser cavity 24 is filled with a lasin medium 26 such as CO_ or other gases or mixtures o gases.
• the lasing medium is preferablv contained withi cavity 24 under pressure and the respective ends of th waveguide laser 10 are provided with windows or the lik for sealing the laser cavitv 24 in order to contain th lasing medium. It will, of course, be understood tha the ends of the waveguide laser are also provided wit one total reflector or grating and one outcoupler mirro according to customarv practice.
• RF energy is pumped through fee through 22 with second sidewall 14 grounded so as t establish an electric potential between the meta electrode sidewalls 12 and 14.
• discharge occurs causing the lasin medium to form a plasma, and causing lasing to occur
• the RF excitation is in a frequency range a approximately 100 MHz.
• EH mode lasing bein established.
• the three ato molecule has different vibrational states which produ different spectral lines in the laser output. In ma aDplications, such as in laser radar applications, sing spectral line output is preferred.
• diffraction grating 28 In order to sele the desired spectral line and filter out the others, diffraction grating 28 mav be placed in the laser be path.
• the diffraction grating has a plurality of groov aligned with the x axis and permits onlv a sing spectral line in the output beam.
• t diffraction grating may be included as line selecti optics in the waveguide resonator.
• the present invention provides a number advantages over conventional circular or squa cross-sectional waveguide lasers.
• the improvement in gas cooling one m compare a 1 x 4 rectangular cross-sectional waveguide the invention with a 2 x 2 square conventional wave ui laser. In both instances, the cross-sectional area the same.
• the 1 x 4 rectangular desi advantageously places the metal electrode sidewalls and 14 in much closer proximity to the center than do the conventional design.
• the center of the waveguide cavitv is 1/2 of dimensional unit from the metal electrode sidewalls.
• the waveguide cavity center is dimensional unit from the metal electrode sidewall Because of the closer proximity of the metal electro sidewalls to the center of the waveguide cavity, t invention can dissipate heat from the center mo efficiently than the conventional square or circul design can. This allows the laser of the invention to operate at much higher power levels than conventional designs.
• the rectangular cross-sectional waveguide laser is better spectral line resolution.
• diffraction gratings are sometimes used to select a particular spectral line in certain applications.
• the intergroove spacing of the diffraction grating is dictated bv the wavelength of the spectral line to be selected.
• the diffraction grating of the rectangular configuration can have a considerably greater number of grooves than can a square diffraction grating, because the y dimension of the rectangular grating is greater than that of the square grating.
• the greater number of grooves for a given cross-sectional area gives the invention much better spectral line resolution, with the optical field of the laser able to couple to a larger number of grooves on the diffraction grating.
• Still another advantage of the invention is that it requires lower voltages, due to the fact that the metal electrode sidewalls 12 and 14 are placed more closely together for a given cross-sectional area. This means that a stronger electric field can be established in the waveguide cavitv at a lower voltage. The lower voltage required, decreases the probability of arcing damage.
• the invention is capable of a larger frequency tuning range.
• the tuning frequency of a laser is controlled by the pressure of the gaseous lasing medium. As the pressure increases, however, the electric field required for lasing increases.
• ⁇ ⁇ ., + i ⁇ ? is the dielectric constant of the waveguide sidewalls 16 and 18.

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• Physics & Mathematics (AREA)
• Electromagnetism (AREA)
• Engineering & Computer Science (AREA)
• Plasma & Fusion (AREA)
• Optics & Photonics (AREA)
• Lasers (AREA)
• Polymerisation Methods In General (AREA)
• Polyurethanes Or Polyureas (AREA)
• Macromonomer-Based Addition Polymer (AREA)

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• 1987
  • 1987-12-14 JP JP63500960A patent/JPH01502227A/ja active Pending
  • 1987-12-14 EP EP88900738A patent/EP0302903A1/de not_active Withdrawn
  • 1987-12-14 WO PCT/US1987/003296 patent/WO1988006357A1/en not_active Application Discontinuation
  • 1987-12-23 IL IL84931A patent/IL84931A0/xx unknown

Non-Patent Citations (1)

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