Distributed-feedback quantum cascade lasers emitting in the 9-<i>μ</i>m band with InP top cladding layers

Two different high performance quantum cascade distributed-feedback lasers with four quantum-well-based active regions and InP top cladding layers are presented. The first device, which emitted at 9.5 <i>μ</i>m, was mounted junction down in order to get high average powers of up to 71 mW at -30°C and 30 mW at room temperature. The other device, which lased at 9.1 <i>μ</i>m, was optimized for high pulsed operating temperatures and tested up to 150°C at 1.5% duty cycle. The emission of both lasers stayed single mode with more than 20-dB side-mode suppression ratio over the entire investigated power and temperature range.