Optical: systems and elements – Collimating of light beam
Patent
1997-09-02
1998-09-15
Epps, Georgia Y.
Optical: systems and elements
Collimating of light beam
G02B 2730
Patent
active
058088032
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to an arrangement for collimation of radiation from optoelectrical components in two coordinate directions which are perpendicular to one optical axis and which are perpendicular to one another and for subsequent focussing with high radiation density.
It is known that the radiation of a semiconductor diode laser is characterized by a strongly diverging beam, in contrast to other conventional laser beam sources with a laser beam which has a diameter of a few millimeters with low beam divergence in the range of a few mrad. A semiconductor diode laser has a divergence which is greater than 1000 mrad.
To be able to use the radiation of a semiconductor diode laser, collimating and focussing microoptics or optical arrangements are necessary. Here it can also be considered that a semiconductor laser diode conventionally has several emitters or emitter groups in a row at a distance of a few 100 microns. In the design of an optical arrangement or microoptics, it must therefore be considered that the lenses used must be provided so densely on the respective semiconductor diode laser or on the corresponding laser arrangement or on the chip that the laser radiation of the individual emitters or emitter groups is not superimposed before entering the optical arrangement, since otherwise due to unallowable or unsuitable angles of incidence the scattered radiation causes major radiation losses. In semiconductor laser diodes the divergence angle in the plane perpendicular to the active layer (fast axis) is greater than in the plane of the active layer (slow axis). This difference must be considered in the design of the optical arrangement.
Collimation of the diverging laser radiation from emitters or emitter groups using two cylindrical lenses arranged in succession in one optical axis is known, by the first cylindrical lens collimation taking place in the fast axis, i.e., in the axis perpendicular to the plane of the active layer, and by means of a second cylindrical lens farther away from the laser diode arrangement collimation in the slow axis taking place.
In particular, an optical arrangement (U.S. Pat. No. 3,396,344) is known in which there are several laser diodes or emitters or emitter groups in at least two rows on top of one another, each row in the first coordinate direction in the plane of the active layer having several emitters or emitter groups, and the two rows in the second coordinate direction being offset against one another perpendicular to the active layer. For collimation of the individual beams for each row there is a first cylindrical lens as the collimation optics, that is, for collimation in the second coordinate direction (fast axis). For collimation in the first coordinate direction (slow axis) a cylindrical lens arrangement which forms second collimation optics has several cylindrical lens elements which are provided such that each of these cylindrical lens elements takes effect for the laser beams of two emitters which are located on top of one another and which are assigned to one another in the two adjacent rows and are directly adjacent to one another.
The adjacent cylindrical lens elements, in the first collimation optics, and especially in the second collimation optics, require a certain lens height and certain radius of curvature and also certain special spatial dimensions for the desired collimation, a relatively great distance of the individual emitters or emitter groups in each row is necessary. This means a relatively small occupation density of the chip which forms the laser diode arrangement, although in terms of chip technology and with respect to the development of high-power coolers a much higher occupation density and thus much higher output power would be possible. The disadvantage in the known optical arrangement and especially with a host of emitters or emitter groups in each line, imaging or focussing of the laser beams occurs at the focal point, in which the focal diameter in the first coordinate direction is greater than
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Kosters Arnd
Krause Volker
Ullmann Christopher
Epps Georgia Y.
Mack Ricky
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