US H2161 H1
Visible light-emitting-diodes (LEDs) are inexpensive, provide emissions in many wavelengths and are powerful enough to pump solid state laser rods. The LED light is directed to the laser rod (laser gain element). The LED wavelength chosen matches the absorption spectrum of a transition element contained in the laser rod. It is know that the absorption bandwidths of these elements are typically very large. Besides a single LED, an array of LEDs may be used. Either of these arrangements may be imaged on the laser rod or fiber-coupled to the rod. A laser system that is pumped by one or more LEDs provides a low cost, relatively low power laser system. A low cost, higher powered, pulsed laser system is possible by pulsed LED operation. Thus it is possible to exceed the pump power threshold for a given laser by using a relatively small number of LEDs.
1. A method comprising the steps of:
providing a solid-state laser rod that includes a transition element; and
providing a visible light-emitting-diode so that light emitted by said diode generates a laser emission in said rod.
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Lasers containing solid state transition element laser rods, such as those containing chromium (Cr) and titanium (Ti), are typically pumped by other lasers, including laser diodes. See for example, U.S. Pat. No. 5,090,019 and U.S. Pat. No. 5,249,189, both of which are issued to the inventor and are incorporated by reference herein. It is known that transition element doped lasers typically absorb pumping radiation at shorter wavelengths (in general) than rare-earth doped lasers, such as neodymium (Nd) or ytterbium (Yb). However laser pump sources in the visible range, such as red for Cr3+ or green for Ti3+, are either very expensive or are non-existent.
While a great deal of research has been conducted in the field of lasers, there is a continual desire to lower their costs.
Visible light-emitting-diodes (LEDS) are inexpensive, provide emissions in many different wavelengths and are powerful enough to pump a solid state laser rod. In accordance with the invention, LED light is directed to the laser rod, otherwise known as the laser gain element. The LED wavelength is selected to match the absorption spectrum of a transition element contained in the laser rod. It is know that the absorption bandwidths of these elements tend to be very large. Besides a single LED, an array of LEDs may be used. Either of these arrangements may be imaged on the laser rod or may be fiber-coupled to the rod. A laser system that is pumped by one or more light-emitting-diodes provides a low cost, relatively low power, laser system. A low cost, higher powered, pulsed laser system is made possible by pulsed LED operation. Thus it is possible to exceed the pump power threshold for a given laser by using a relatively small number of LEDs to pump the laser.
An object of this invention is to provide a laser system that is of relatively low cost.
A further object of this invention is to provide an optical pump system designed for use with transition element doped solid-state laser rods.
Still a further object of the invention is to provide a laser system designed for use with transition element doped solid-state laser rods wherein laser pumping is provided by one or more light-emitting-diodes.
Other objects, advantages and new features of the invention will become apparent from the following detailed description when considered in conjunction with the accompanied drawings.
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The nature of the transferring optics, coatings, laser rod specifications, cavity length and mirror configuration are considered within the skill of artisans of this field. It should be noted that because LEDs are less directional in their emission when compared to laser-based pumping sources including laser diodes, larger aperture, higher numerical aperture (NA), optics will be required to appropriately collect the LED light.
As described above, the LED or LEDs may be powered to operate continuous wave to produce a continuous laser emission or may be powered to operate pulsed to produce a pulsed emission in the laser being pumped. When pulsed, the LEDs produce much higher power for short periods of time, allowing high pulsed power of a laser. For example, a 1 milli-Watt output normally continuous wave LED when pulsed at pulse widths of less than 100 nanoseconds can emit approximately 5 to 50 watts for short periods of time (about 100 nanoseconds). This allows higher power, pulsed operation of a laser system employing the pulsed LED(s). Laser rods that may be LED pumped in the red are, for example, those of Cr:LiSAF. Laser rods capable of LED pumping in green as well as blue are, for example, those of Ti:Al2O3.
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Though the transition elements chromium and titanium have been described above by way of example, the invention is not considered restricted to these. All transition elements are considered suitable for application in this invention. Similarly, though in some instances of the examples given above a single LED is shown or a plurality of LEDs are shown, one can envision that in appropriate applications a reverse usage may be fitting so that a plurality of LEDs is substituted for the single LED and vice-versa. Where a plurality of LEDs are used, one may turn to semiconductor technology to enable these LEDs to be produced lithographically on a single semiconductor substrate, thus producing a monolithic array. Fiber optics, utilizing single fibers and/or fiber bundles, may be employed with these configurations.
Obviously, many modifications and variations of the invention are possible in light of the above description. It is therefore to be understood that within the scope of the claims the invention may be practiced otherwise than as has been specifically described.