Symmetric far field, short-wavelength (λ = 4.53 μm) MOPA quantum cascade lasers with Watt-level optical output power

Full text: We present the design and first realization of short-wavelength (λ = 4.53 μm), single mode emitting quantum cascade lasers in a master oscillator power amplifier configuration. Watt-level peak optical output power is demonstrated for typical non-tapered 4 μm wide and 5.25 mm long (DFB: 1.25 mm, FP: 4 mm) devices. Far field measurements prove a symmetric, single-transverse-mode emission in TM00-mode with typical divergences of 25° in and 27° perpendicular to the growth direction. We demonstrate single mode tuning over a range of 7.9 cm-1 for temperatures between 263 K and 313 K and also single mode emission for different driving currents and varied pulse-lengths between 25 ns and 100 ns. The side mode suppression ratio is measured to be higher than 20 dB. (author)