Optical: systems and elements – Collimating of light beam
Reexamination Certificate
1999-02-24
2001-06-05
Sugarman, Scott J. (Department: 2873)
Optical: systems and elements
Collimating of light beam
C359S618000, C359S619000, C359S629000
Reexamination Certificate
active
06243210
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the general field of semiconductor laser systems using diode bars and stacked diode bars, providing high-brightness beams, used in applications such as pumping of solid-state lasers, materials processing and medical applications. Specifically, this invention relates to an optical image rotation device, and the associated laser and optical systems.
2. Description of the Prior Art
Various systems previously designed to modify the bi-lateral divergence of laser diodes and laser diode arrays use sequential image rotation devices, which depend on a specific and predetermined order of reflective surfaces. Specifically, each laser diode image is rotated by an individual and specific series of optical elements. Examples of these optical elements include prisms, external reflectors and lenses. Due to the relatively small spacing between individual diode emitters, and the subsequent relatively small spacing between subsequent adjacent beampaths, the aforementioned optical elements are relatively small, and generally assembled in an array of size on the scale of the laser diode array. Fabrication and assembly of such arrays of optical elements is relatively complex, as compared to the use of a single lens element. Careful alignment of such an optical element array must be performed to achieve optimal performance of the system as a whole. In U.S. Pat. No. 5,513,201, “Optical Path Rotating Device Used With Linear Array Laser Diode And Laser Apparatus Applied Therewith”, several externally and internally reflective array designs are presented, all of which require careful one-to-one alignment with the laser diode array.
SUMMARY OF THE INVENTION
The present invention provides a new optical image rotating device, used in combination with laser diode bars or laser diode bar arrays, cylindrical lens elements or cylindrical lens element arrays, and an afocal image relay system, to achieve a highly collimated output laser beam suitable for use in many applications.
The optical image rotating device comprises a plurality of pairs of perpendicular reflective surfaces. This device may be a mirror array, prism array, or a plurality of prisms. The working surfaces of the optical image rotating device are perpendicular to a common plane, so that fabrication of the optical image rotation device is relatively easy and straightforward. The optical image rotation device is suitable for use with high density laser diode bars, as well as continuous linear and 2D sources. Performance of the system is relatively insensitive to alignment of the optical image rotation device.
In the first embodiment, semiconductor laser sources, comprising a laser diode bar having arranged linearly therein 10 to 100 active layer stripes, are collimated in the fast axis by a single cylindrical lens element. An afocal image relaying optical system then reimages the laser diode bar through a polarizing beamsplitter onto the optical image rotating device. The optical image rotating device rotates the image, and therefore the associated polarization, 90 degrees around the Z-axis. The optical image rotating device reflects and redirects the radiation back towards the polarizing beamsplitter. The polarizing beamsplitter reflects and redirects the beam in a direction substantially different from the incident beam. A single cylindrical lens subsequently collimates the beam in the slow axis. The laser diode bar radiation is therefore brought to a high degree of collimation, and can be readily used in many applications.
In the second embodiment, semiconductor laser sources, comprising a stack of laser diode bars having arranged linearly therein 10 to 100 active layer stripes, are collimated in the fact axis by a stack of cylindrical lens elements. An afocal image relaying optical system then reimages the stack of laser diode bars, through a polarizing beamsplitter, onto the optical image rotating device. The optical image rotating device rotates the image, and therefore the associated polarization, 90 degrees around the Z-axis. The optical image rotating device reflects and redirects the radiation back towards the polarizing beamsplitter. The polarizing beamsplitter reflects and redirects the beam in a direction substantially different from the incident beam. A stack of cylindrical lens elements subsequently collimates the beam in the slow axis. The radiation from the stack of laser diode bars is, therefore, brought to a high degree of collimation, and can be readily used in many applications.
REFERENCES:
patent: 4969137 (1990-11-01), Sugiyama et al.
patent: 5168401 (1992-12-01), Endriz
patent: 5513201 (1996-04-01), Yamaguchi et al.
patent: 5532730 (1996-07-01), Akanabe
patent: 5579161 (1996-11-01), Sekiguchi
patent: 5850307 (1998-12-01), Straayer
Jaeger Hugh D.
Semiconductor Laser International Corp.
Sugarman Scott J.
Thompson Tim
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