U.S. Air Force scientists have created a novel manufacturing process to produce much improved nanodiamond surfaces to cool laser diodes.
The ability to cool a laser diode has been widely recognized as a limitation of current day ability to convert electrical energy into coherent radiant energy in a small space. Since present day laser diodes operate in the realm of fifty percent or lower electrical energy to light energy conversion efficiency and laser diode operation in the temperature range around room temperature are usual factors incurred in laser operation, it is easy to comprehend that efficient removal of unconverted electrical energy proceeds or energy losses, i.e., heat, from a for example, laser bar structure is highly desirable.
US Air Force (Washington, DC) scientists Dr. Shlomo Z. Rotter and Susan L Heidger have created a three step process to form nanodiamond coolers that result in a mounting improvement for solid state laser bars. The laser bars are used to pump high power lasers. The nanofabrication method is disclosed in U.S. Patent 7,586,962.
The Integrated Diamond Carrier is described as a freestanding diamond baseplate or carrier consisting of an array of mesa structures for mounting solid state (e.g. GaAs) laser bars and mirrors for steering the generated laser light. The Integrated Diamond Carrier is formed by conformally growing diamond on a patterned substrate of for example silicon that serves as a mold or template. The substrate is etched away leaving the freestanding diamond carrier. The conformal growth of diamond is important to the successful fabrication of the Integrated Diamond Carrier.
Solid state laser bars are mounted in side by side relationship and combined with integrated substrate and laser output directing optical elements on an Integrated Diamond Carrier.
The Integrated Diamond Carrier is preferably fabricated as an essentially freestanding base plate of diamond composition with incorporated arrays of mesa structures providing mounting for the laser bars and provides integral laser output directing optical elements such as mirrored prisms. Integrated diamond carriers provide stable positioning, desirable thermal conductivity and consistent low temperature operation for the solid state lasers.
Rotter and Heidger developed a growth sequences using the Astex 5 KW Microwave High Growth Chemical Vapor Deposition Diamond System, a system operating at a microwave frequency of 2.45 gigahertz. Alternately a hot filament reactor growth chamber apparatus using a rod array filament, an apparatus known in the deposition art may be used.
A controlled growth process is used to obtain a very dense diamond film at the diamond/substrate interface while growing an Integrated Diamond Carrier according to Rotter and Heidger. Dr. Rotter's process may be referred-to by the acronym NNP (novel nucleation process).
The NNP process is helpful but not entirely successful in growing the dense interface needed for the Integrated Diamond Carrier. This partial success may in part be attributed to interaction with the presently preferred plasma assisted microwave chemical vapor deposition system used for diamond growth. Other nucleation and film growth techniques have been described in the literature and may also be suitable for growing the dense conformal diamond coating for the Integrated Diamond Carrier.
The NNP process is helpful but not entirely successful in growing the dense interface needed for the Integrated Diamond Carrier. This partial success may in part be attributed to interaction with the presently preferred plasma assisted microwave chemical vapor deposition system used for diamond growth. Other nucleation and film growth techniques have been described in the literature and may also be suitable for growing the dense conformal diamond coating for the Integrated Diamond Carrier.
The modified novel nucleation process (or MNNP) is a three-step sequence for achieving a high nucleation rate of diamond on a multitude of substrates and obtaining a dense smooth interface.
FIG. 4 shows surface roughness details of an Integrated Diamond Carrier deflecting element mold. FIG. 5 shows an example of surface roughness details of an Integrated Diamond Carrier deflecting element surface. FIG. 6 shows an example of surface roughness details for a laser bonding pad portion of an Integrated Diamond Carrier.
Integrated Diamond Carrier can be utilized in a variety of packages for a variety of devices and modules in addition to lasers. For example, Integrated Diamond Carriers may employ mold or template fabrication materials other than silicon and may be utilized in the packaging of MicroElectro Mechanical Systems (MEMS) and Micro Optical Electro Mechanical Systems (MOEMS) devices, particularly where such devices can benefit from carriers customized to particular applications. Integrated Diamond Carriers may also find use in the mounting and cooling of semiconductor devices particularly power semiconductor devices and semiconductor devices employing optical input or output communication paths.
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