Laser diode stacks: pulsed light power for nuclear fusion

Abstract

Laser drivers are an enabling factor to inertial confinement fusion, because laser diodes must be used instead of flash lamps. We discuss the limitations of laser diode arrays and show what steps the industry is taking. The pump power requirements of large-scale projects such as LIFE or HiPER are within reach of semiconductor laser diode assemblies. Pulsed light output powers per laser bars have been around 300 W per bar, as in the Jenoptik 940 nm bars previously used for pumping the Yb:YAG slabs in the DiPOLE project. By redesigning the semiconductor laser structures 500 W per bar is now commercially available for 808, 880 and 940 nm pump wavelengths. The construction of one inertial fusion power plant will require an amount of semiconductor laser chips in excess of the current annual production by two orders of magnitude. This adds to the engineering task of improving the device characteristics a challenge to production capacity. While the industry benefits from the recent boost in solid-state lighting that acts as a technology driver, cooperation between manufacturers will be imperative, and to this end we propose standardization efforts.

Diode pumps for future laser plasma accelerators: perspectives from research and industry

“…Several industrial suppliers have publicly reported multi-100 kW diode laser pump modules for high-energy-class laser systems, and a brief summary of current status was recently presented at the 6 th European Advanced Accelerator Concepts (EAAC) workshop [19], collecting input from TRUMPF, due to their role as providers of pumps for DIPOLE [17,20], Leonardo, due their role as providers of pumps for HAPLS [21] and Coherent and Jenoptik, due to their publication record on supply of pumps for high-energy-class systems [22,23]. Other suppliers are also active (e.g.…”

“…In contrast, although the bars in water-cooled QCW stacked arrays can operate with Popt = 400…600 W, the cooling configuration (one water cooler for many 10's of bars) is typically only suitable for use in low-duty cycle operation of around 1%, limiting the achievable repetition rate of the coolers to f = 20 Hz or less. Higher duty cycle operation rates up to 6% are achievable by a properly adapted design, that increases the spacing of the bars (fewer bars and hence less peak power per cooler) [22]. 2D-arrays of rear-edge cooled QCW stacks with emission power in the many 100's of kilowatts are available from several suppliers for build of large systems, with an example shown in Fig.…”

Novel High-Power, High Repetition Rate Laser Diode Pump Modules Suitable for High-Energy Class Laser Facilities

“…Commercially available pump sources that can potentially deliver these parameters consist of stacks or arrays of high-energy class diode lasers (HEC-DL) in 1-cm bar format, with each bar combined with a fast axis collimation (FAC) lens. The bars are collected into pump modules, including customised optics for beam shaping and homogenizing [7][8][9][10][11][12]. There are two main configurations.…”

“…For example, some publications focus on other wavelengths than =940 nm (e.g., =808 nm), but these modules can very likely be modified for similar performance at 940 nm. Also shown is the optical brightness B of the pump, where the emission aperture was either directly taken from the reference or calculated by the authors as in [8] from the emitting area (integrated over all emitters in the module). The solid angle was also calculated following [5], using the lateral and vertical divergences angles with 95% power content.…”