Distributed-feedback quantum cascade lasers emitting in the 9-μm 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 μm, was mounted junction down in order to get high average powers of up to 71 mW at -30/spl deg/C and 30 mW at room temperature. The other device, which lased at 9.1 μm, was optimized for high pulsed operating temperatures and tested up to 150/spl deg/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.