Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Patent
1997-06-03
1999-03-02
Epps, Georgia Y.
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
G02B 2710
Patent
active
058778985
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
a) Field of the Invention
The invention is directed to an arrangement by means of which the radiation of a plurality of laser diode lines is combined and shaped in order, for example, to couple into an optical fiber or into the end face of a solid-state laser rod. This is a laser diode line light source which can be advantageously used, for example, in laser surgery, laser material processing or for pumping solid-state lasers.
b) Description of the Related Art
Laser diodes are distinguished from other lasers particularly by their high efficiency which is, however, combined with high current densities that allow only very small dimensions and accordingly limited output power.
Therefore, in many cases of application in which a higher laser output is needed, it becomes necessary to use the radiation output of a plurality of laser diodes which are combined in a corresponding manner.
High radiation quality, which is determined by the dimensioning of the beam cross section and the far-field divergence of the radiation, is required particularly when the combined beam bundle is to be coupled into a device or optical element following downstream.
The cross section of the emission surface of approximately 1 .mu.m.times.100 .mu.m in laser diodes results in an asymmetrical cross section for the respective emitting beam bundle with a longitudinal axis of approximately one hundred times the length of the transverse axis. This asymmetry is multiplied in the case of the radiation of a laser diode line due to the arrangement of individual emission surfaces on a straight line along their longitudinal axes as is required for technological reasons and reasons relating to cooling technique. In addition to the resulting unfavorable beam geometry, there is the widely different divergence of the radiation in the longitudinal axis and transverse axis. As is well known, the divergence of the laser diode radiation in the direction of the transverse axis, perpendicular to the plane of the pn junction of the laser diode, is as much as 90.degree., whereas it amounts to only approximately 10.degree. in the direction of the longitudinal axis, that is, parallel to the plane of the pn junction. The highly asymmetrical beam geometry and the divergence of the beam bundle of a laser diode line results in exacting requirements for an arrangement for combining and shaping radiation that must ultimately generate a beam bundle adapted to the aperture of the optics following downstream in order to achieve high in-coupling efficiency.
OBJECT OF THE INVENTION
The primary object of the invention is to provide a novel arrangement by which the radiation of a plurality of laser diode lines is so combined and shaped that the combined beam bundle has the smallest possible cross section with the least possible asymmetry and far-field divergence.
This object is met in an arrangement in accordance with the invention, an arrangement for combining and shaping the radiation of a plurality of laser diode lines comprising at least two laser diode lines whose radiation has a cross section in the emission plane (x-y plane) whose longitudinal axis is a multiple of the transverse axis, a collimator unit of each laser diode line in the radiation direction, a combining unit for combining the collimated radiation of the individual laser diode lines by means of a side-by-side arrangement in the direction of the transverse axis, and a recombining unit for dividing the combined radiation in the direction of the longitudinal axes into individual partial beams and recombining the latter by means of a side-by-side arrangement in the direction of the transverse axes.
The invention is based essentially on the selection and sequence of the arrangement of optically active means for shaping, deflecting, dividing and combining the radiation from a plurality of laser diode lines to form a beam bundle. For this purpose, it is critical that the following means be arranged downstream of the laser diode lines in the following sequence in the direction of
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Optics Letters, Jan. 15, 1995--Article "Stripe For Use With Laser Diode Bars" R.P. Edwin (pp. 222-224).
Optics Letters, Apr. 15, 1995--Article "Collimation of Emissions From a High-Power Multistrip Laser-Diode Bar With Multiprism Array Coupling and Focusing to a Small Spot" S. Yamagichi (pp. 898-890).
Conference on Lasers and Electro-Optics (Cleo) May 8-13, 1994, Anaheim, CA Novel Beam Shaping Technique for High Power Diode Bars: W.A. Clark, et al (p. 360).
Chaleev Michail Michailovic
Hollemann Guenter
Mak Arthur Afanasevic
Michailov Aleksej Vadimovic
Novikov Georgij Egorovic
Epps Georgia Y.
Jenoptik Aktiengescellschaft
Mack Ricky
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