Cryogenic High Power Laser Pump Diodes

ABSTRACT: Directed Energy Solutions (DES) is proposing to develop a cryogenically cooled diode laser stack system. In the proposed effort DES will design, fabricate, test and delivery a cryogenically cooled multiple diode laser stack system. Output powers of the laser system of 6 kW are anticipated with a scaling option at the 12 kW level. At the end of proposed effort the system will be delivered to AFRL/RDLS for testing and evaluation. The proposed effort will leverage past and present DES programs on high power solid-state laser and cryogenic laser systems. BENEFIT: There are several key technologies that will be developed during the proposed multiple phase program which possess significant commercialization opportunities. These technologies are: • Cryogenic Solid-State Lasers • Narrow Linewidth Diode Laser Bars • Widely Tunable Diode Laser Devices (smaller market, not discussed below) DES is developing multiple products based on the key technologies and upon completion of these devices will seek VC funding to bring these devices to market. Incubic is one venture fund that DES has experience with and would contact about possible product funding. Each of these technologies commercialization potential will be discussed below. Cryogenic Solid-State Lasers: The developed diode pump technology can be applied to virtually any solid-state material which results in a variety of emission wavelengths. For instance, high power devices can be demonstrated in Yb (~1030 nm), Nd (~1060 nm), Er (~1600 nm, and 2940 nm), Tm (~2100 nm) and Ho (~2000 nm). These efficient, compact, high power laser devices with excellent beam quality are in great demand as can be seen by the variety of industrial, academic and military based applications. • Asset protection – A high average power eye-safe laser would allow for the protection of US assets against rockets, artillery, and mortars with a significantly reduced risk of collateral eye damage. The compact and self-contained design of a 100 kW device would allow for a variety of tactical platforms to be used such as UAV, and ground based vehicles. • LIDAR/LADAR – High average power LIDAR/LADAR systems can be made using Er, Tm, and Ho as possible hosts. In the case of the relatively long excited state lifetime of Er:YAG (10 ms) laser systems with repetition rates of 100 Hz can be made. This enables a multi joule per pulse laser system with a moderate power master oscillator. This high energy, coupled with near diffraction limited beam quality is ideal for high resolution LIDAR/LADAR at a distance. This device would have industrial, academic and military based customers • Pump Lasers – Frequency doubling of a cryogenic Yb:YAG would allow for efficiency high energy pumping of Ti:Sapphire. The variable pulse repetition frequency and pulse length make this type of laser source ideal for pump an fs Ti:Sapphire amplifier. In addition high power OPOs can be made with these efficient pump sources • Spectrally diverse lasers - The cryogenic solid-state laser is an ideal pump source for high energy Raman lasers. These lasers can be operated continuous wave or pulsed. The variety of Raman active materials would enable nearly complete spectral coverage from the visible to the mid-wave infrared. DES is developing a 30 W cryogenic Yb:YAG laser which can be operated continuous wave and pulsed. Upon completion of this device, DES will seek out VC funding to produce the product targeting the aforementioned markets. Incubic is one venture fund that DES would contact about possible product funding. Narrow Linewidth Diode Laser Bars The development proposed in this multi phase effort can also be applied to narrow linewidth diode laser bars and stacks. Narrow linewidth diode laser bars has clear commercialization potential for optical pump sources for solid-state lasers such as Er:YAG and Yb:YAG (970 nm line). In addition, Alkali metal lasers may also require narrow linewidth pump lasers for efficient operation. DES has extensive experience in the production of optical singlet delta oxygen (SDO) using linewidth narrowed diode laser bars. This SDO technology kills bacteria and viruses and oxidizes VOCs and other chemical agents by using only air (oxygen) and light (from diodes). Therefore, it represents a unique capability for sterilization, decontamination, pollution mitigation, and air quality improvement applications in hospitals, homes, commercial buildings, manufacturing and power generation plants, and government installations and vehicles. Its effectiveness in killing cells is steeped in 20 years of research associated with Photodynamic Therapy where SDO is used to kill tumorous tissue in a light activated cancer treatment. Its usefulness in oxidizing chemicals to safe products is well established. What has been lacking is an effective way to make SDO in the air in large quantities. DES has overcome this last obstacle to commercialization.