High power diode lasers are increasingly important in many industrial applications. However, an ongoing challenge is to simultaneously obtain high output power, diffraction-limited beam quality and narrow spectral width. One approach to fulfill these requirements is to use a “master oscillator - power amplifier (MOPA)” system. We present recent data on MOPAs using PA designs that have low confinement factor (1%), leading to low modal gain, and low optical loss (<0.5cm<sup>-1</sup>). Quantum barriers with low refractive index are used to reduce the optical waveguiding due to the active region, which should decrease susceptibility to filament formation. A truncated tapered lateral design was used. Conventional tapered designs have a ridge waveguide (RW) at the entrance of the devices with etched cavity- spoiling grooves at the transition to the tapered gain region. Our amplifier used a truncated tapered design with no RW entrance section. We show that for this approach cavity-spoiling grooves are not necessary, and achieve improved performance when they are omitted, which we attribute to the filament insensitivity of our structure. High beam quality was achieved from a 970nm amplifier with M<sup>2</sup> (1/e<sup>2</sup>) = 1.9, with efficiency of <48% in QCW condition, and <17W diffraction-limited beam maintained in the central lobe. The impact of the in-plane geometrical design was assessed and we show that large surface area is advantageous for device performance. The spectral properties of the amplifier replicated that of the DBRtapered laser, which is used as the master oscillator, with a spectral width of <30pm (FWHM). Design options for further increases in power are presented.
High power diode lasers are the root source of optical energy in all high performance laser systems. As their performance
advances, diode lasers are increasingly taking the place of other sources. Short pulse, sub-microsecond-class, high power
lasers are important for many applications but historically, diode lasers have not been able to reach high enough peak
pulse powers with adequate reliability, limited by physical effects such as facet failure. By combining robust facet
passivation with thick super large optical cavity waveguides, greatly increased optical output power can be achieved. We
present here the results of a study using commercial high current short pulse sources (>200A, <500ns) to assess the
performance and endurance limits of high power broad area devices. We find that our lasers can be driven with a peak
power density of over 110MWcm<sup>-2</sup> without failure for more than 3×10<sup>7</sup> pulses. For example, on testing to 240A, single
emitter 200μm stripe 1100nm broad area devices reach 124W (46μJ) without failure, and 60μm stripes reach 88W. In
practice, high injection effects such as carrier accumulation in waveguide typically limit peak power. We review these
remaining limitations, and discuss how they can be overcome.