High-average-power diode-pumped Yb:YAG lasers

Abstract

A scaleable diode end-pumping technology for high-average-power slab and rod lasers has been under development for the past several years at Lawrence Livermore National Laboratory (LLNL). This technology has particular application to high average power Yb:YAG lasers that utilize a rod configured gain element. Previously, this rod configured approach has achieved average output powers in a single 5 cm long by 2 mm diameter Yb:YAG rod of 430 W cw and 280 W q-switched. High beam quality (M 2 =2.4) q-switched operation has also been demonstrated at over 180 W of average output power 1 . More recently, using a dual rod configuration consisting of two, 5 cm long by 2 mm diameter laser rods with birefringence compensation, we have achieved 1080 W of cw output with an M 2 value of 13.5 at an optical-to-optical conversion efficiency of 27.5%2 . With the same dual rod laser operated in a q-switched mode, we have also demonstrated 532 W of average power with an M 2 <2.5 at 17% optical-to-optical conversion efficiency. These q-switched results were obtained at a 10 kHz repetition rate and resulted in 77 nsec pulse durations. These improved levels of operational performance have been achieved as a result of technology advancements made in several areas that will be covered in this manuscript. These enhancements to our architecture include: (1) Hollow lens ducts that enable the use of advanced cavity architectures permitting birefringence compensation and the ability to run in large aperture-filling near-diffraction-limited modes.(2) Compound laser rods with flanged-nonabsorbing-endcaps fabricated by diffusion bonding. (3) Techniques for suppressing amplified spontaneous emission (ASE) and parasitics in the polished barrel rods.

Applications of High Power Semiconductor Lasers

“…For higher output power, multiple diode lasers with complex beam shape and focus optical system are used as pump source as shown in Fig. 10.9b [7]. As mentioned above, the diameter of the rod is usually small, so the maximum pump power depends on the damage threshold of the gain media.…”

“…When an open package diode laser is used for a pumping source, a focus system is needed to focus the laser beam into the rod, as shown in Fig. 10.9b [4,7]. For higher output power, multiple diode lasers with complex beam shape and focus optical system are used as pump source as shown in Fig.…”

“…The semiconductor laser as the pump source of the end-pumped rod laser can be focused into the rod through an imaging system. Figure 10.9a shows a typical pumping structure which uses a fiber-coupled LD module as the pump source [4,7]. The beam out of the fiber is focused into the rod through an imaging system.…”

Laser Research and Development Studies for Laser Guide Star Systems

“…11 was previously developed and demonstrated at a larger scale for a 1 kW Yb:YAG laser that we developed for Boeing. 16 This system, shown in Fig. 12 uses a "hollow lens duct" (HLD) pump delivery architecture to funnel diode pump light into the end of a laser rod with an overall pump .…”

LD side-pumped passively Q-switched Yb:YAG slab laser

“…Among them, the trivalent ytterbium ion seems to be the most attractive candidate as its electronic structure is limited to only two levels avoiding the excited states absorption, up conversion and concentration quenching. Recent literature verify enormous potential for CW high power and high efficiency of Yb:YAG lasers [1][2][3][4] and Yb:YAG microchip lasers [5,6] because of the good laser properties of Yb ion and mechanical properties of the hosting YAG.…”