Industrial lasers require cooling to remove excess heat generated in the resonator power electronics and the optics system. The type of cooling required is determined by laser wattage, resonator efficiency, resonator and optics temperature requirements, and ambient temperature.
For some applications, resonator and optics operating temperatures are always above ambient temperature and the heat load is low, so components can be air cooled with fans. However, this method is generally limited to relatively low heat fluxes and offers limited temperature stability. When heat flux exceeds the capabilities of direct air cooling, laser systems may use liquid-to-liquid cooling chillers, in which a pump circulates process water through the system to remove heat, transferring it to a chilled facility water system via a heat exchanger.
For laser systems requiring the resonator and optics operating temperatures to be at or below ambient, vapor compression (VC) water chillers are typically used. These chillers use a refrigeration system, which includes a compressor, condenser, expansion valve, and evaporator. They transfer heat from the process cooling water to the air through an air-cooled condenser or to a facility chilled water system through a water-cooled condenser. VC water chillers can handle high heat loads and, when equipped with the proper control systems, hold process cooling water within <±0.5°F.
Laser system performance is affected by increased temperatures. As operating temperatures increase, the laser wavelength also increases, reducing overall optical conversion efficiency. It is critical for the wavelength of light energy from each emitter to be within a very narrow band. Proper cooling helps maintain the beam alignment in front of the emitter.
High-powered industrial lasers require a strong beam focus. Unfortunately, these applications often see wide fluctuations in heat load, which can cause overheating of key laser components. Cooling at a consistent, precise temperature improves beam quality and protects the laser system.
With solid-state technology, laser systems are able to produce continuous high-output power, increased speed, and more precise beam quality. Chiller manufacturers must meet the demand for higher uptime, precise temperature control, higher energy efficiency, and a smaller footprint. Laser manufacturers are also adding refrigeration systems directly into the laser system. Since laser systems require cooling for many components, multiple cooling circuits are often needed. Traditionally, this required dedicated chillers for each circuit. However, integrating two or three cooling circuits into one uses less electricity, reduces system footprint, and minimizes installation costs.
For example, the Intelligent Laser Cooling System (iLCS) from Glen Dimplex Thermal Solutions incorporates technology to integrate better with customer’s equipment and takes less time to install, set up, and operate. Using machine-to-machine communication linked to a customer’s building management systems, built-in electronic sensors monitor tank levels, deionized water quality, and fluid pressure and flow in order to alert users of chiller health and predictive measures needed to prevent downtime. The controller automatically adjusts the motorized hot gas bypass to modulate the refrigeration circuit, enabling precise temperature control.
One refrigeration circuit in the iLCS can cool multiple fluid circuits, eliminating the need for multiple chillers. Also, dual compressors better match variable heat loads, improve efficiency, and reduce component failure.