Coherent light generators – Optical fiber laser
Patent
1991-09-12
1993-11-02
Scott, Jr., Leon
Coherent light generators
Optical fiber laser
372101, 372100, 372106, 372 75, 359669, H01S 330
Patent
active
052589897
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to solid state laser diode light sources for use particularly, but not exclusively, in laser probes for treating tissue in applications such as laser angioplasty and contact laser surgery.
Medical laser devices for the treatment of e.g. blocked arteries are well known. Laser energy is directed through an optical fibre so as to either directly irradiate and destroy tissue, or indirectly irradiate and destroy tissue by heating a thermally conductive tip which contacts and destroys the tissue. In general, such devices have previously used gas lasers or solid state lasers such as Nd:YAG and as such are large and not easily portable. Semiconductor laser diodes have been used in ophthalmic surgery which requires relatively modest optical power (.about.1W) since they provide an inexpensive, compact and robust source of laser light. However they have not been applied to other areas of surgery where higher powers are required because of the difficulty in coupling sufficient laser power from laser diodes into an optical fibre of sufficient flexibility and small diameter for use in surgical applications.
To provide a higher power laser diode light source from an optical fibre it has been proposed to use a plurality of laser diodes.
In one system, the light from each laser diode is fed into a respective optical fibre, a plurality of which are then bundled together to produce the required beam. However commercially available laser diodes produce a stripe source of light (typically 100.times.1 .mu.m) rather than a point source which means that relatively large diameter optical fibres (which are traditionally circular) are required to contain the entire laser stripe, which if bundled together in sufficient numbers to give a suitable power output for surgical use, would result in an assembly which is too large for effective use in conjunction with a medical or surgical probe such as an angioplasty device. It has been proposed to deform the end portion of a circular fibre into a generally oblong shape with the intention that the output of the laser stripe may be more effectively captured and funnelled into a fibre of reduced diameter, but this is an expensive procedure and the funnelling is not energy efficient in practice.
According to a first aspect of the present invention there is provided a laser diode light source comprising at least two solid state laser diodes, a flexible optical fibre, and optical means, interposed between said diodes and said fibre, comprising means for combining the beams produced by said diodes into a combined beam and for focusing said combined beam into said fibre, wherein said optical means comprises an imaging means and anamorphic beam shaping means arranged such that the optical means produces at the fibre end a magnified combined image of the laser stripes of said diodes, the magnification being less in the long direction of the image stripe relative to the magnification in the width direction and being chosen such that the image stripe size in its long direction does not substantially exceed the core diameter of the fibre, the anamorphic beam shaping means being arranged to adjust the relative numerical apertures of the combined beam along said long and width directions such that the numerical apertures in said two directions of the beam focused into the end of the fibre do not substantially exceed the numerical aperture of the fibre.
In accordance with the invention, the optical power transmitted through the or each flexible fibre is increased with the result that a lesser number of fibres of smaller diameter may be conveniently bundled together to provide a source of sufficient brightness for e.g. surgical use within the size constraints imposed by an angioplasty or other medical device. A source in accordance with the invention may have other applications, such as laser soldering irons in which laser light passed through an optical fibre provides the heat for the soldering process. In such an application, the light from two laser diodes focused into a sin
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Diomed Limited
Jr. Leon Scott
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