KEYWORDS: Semiconductor lasers, Packaging, Reliability, Laser development, High power diode lasers, Solid state lasers, Resistance, High power lasers, Corrosion, Continuous wave operation
There are strong demands at the market to increase power and reliability for high power diode laser. In parallel to this the requirements for cooler and package for the high power diode laser increase. Superior heat dissipation capability and low thermal resistance are some of the key attributes for the diode laser package design in the near future. The most common method of removing the large amounts of waste heat in a diode laser is using a micro-channel cooler. However, a microchannel cooler requires water to meet demanding specifications to avoid failures due to corrosion, which increases the overall cost to operate and maintain the laser. We demonstrate advances in a new macro-channel water cooling diode laser which are designed to eliminate the failure mechanisms associated with micro-channel coolers, and enhance the laser heat dissipation and the long-term reliability. For the package adopting the high thermal conductivity material, the maximum output power is 100 W per bar in CW mode. Due to the advantage of compact design, high power, high reliability and fast axis collimation, the new diode laser has the potential to be widely used in many fields, such as pumping solid state laser, hair removal, industry and research.
A high peak power annularly-stacked laser diode pump has been designed and manufactured for a solid state laser (SSL), which is constructed by 12 single annular stacks composed of 3-bar laser diode (LD) submodules. High peak power and high wavelength uniformity have been considered. Macro channel cooling has been used during the operation of the annular stacks, at typical coolant flow rate of 2L/min. Heat dissipation and stress of a single annular stack have been simulated by finite element software, which shows high temperature uniformity of 3-bar submodules (plus or minus 0.5℃) and low package stress (11.8MP).
The peak power of the annularly stacked laser diode pump has reached 234kW at a peak current of 450A or less. A high uniformity of centroid wavelength (802 plus or minus1nm) with a full width at half maximum (FWHM) of 4nm has been measured. More than 24 million shots have been verified for the 3-bar LD submodules.
High power QCW diode laser stacks have been widely used in pumping applications for years. Different package structures of diode laser stacks are applied for pumping the cylindrical rod crystal, such as modular G-Stack, horizontal, vertical and annular arrays. Annular array is preferred in pumping of QCW mode with low duty cycle and short pulse width, due to the advantage of compact structural size, uniform light beam distribution and convenient electric connection. However, the development of annular diode laser array using hard solder is difficult because of the complex bonding process of diode laser on annular heatsink with conventional bonding fixture. Furthermore the stress and thermal behavior is yet to be well studied on the annular diode laser array. In this work, a sophisticated annular diode laser array was developed using hard solder. Optimized structure and thermal design were conducted to achieve uniform light beam distribution and good heat dissipation. Stress release structure of diode laser stack is applied to reduce the risk of chip crack and deviation of spatial spectrum. The annular diode laser array consists of 44 bars in a ring, with the peak output power of each bar over 500W. The maximum output power of each bar reaches 673 W.
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