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We present the design and the performance of midinfrared distributed feedback (DFB) quantum cascade lasers (QCLs) made of strain balanced GaxIn1-xAs/AlyIn1-yAs material on InP substrates for sensing CO2, N2O, and NO in the middle wavelength range of mid-IR from 4 to 6 μm. We present the performances of our DFB QCLs at three different aspects: high power, low threshold power consumption, and wide wavelength coverage. We demonstrated a continuous wave (CW) DFB QCL with an output power of 220mW at 20°C, a CW DFB QCL with low threshold voltage of 8V and low-divergent far-field angles of 27.5° × 32.9° by reducing the number of quantum cascaded stages, a CW DFB QCL with a low threshold power consumption of 0.7W by reducing doping density in the active core, and DFB QCLs wide wavelength coverage of 325 cm-1, 16.9% of center wavelength at 5.2 μm, within one wafer by changing the grating period. 12 DFB QCL chips have being aged for 3000 h under 25°C and a constant quasi-CW current of 0.37 A. No decrease in power was observed.

We studied experimentally and theoretically the substrate-orientation impact on carrier transport and capture in InGaN multiple quantum well (MQW) laser diodes (LDs) with emission in the aquamarine-green spectral range. A new simulation approach was developed to analyze this behavior of LEDs and LDs emitting at these wavelengths. We show that due to deep carrier confinement, the thermal escape from a QW in such devices is negligible. The carrier distribution among QWs is therefore determined by the carrier transport and capture rates. We also show that the ballistic transport mechanism is dominant in this type of MQW active region. In c-plane structures, this mechanism is tunneling-assisted, and therefore, the transport is much slower than in nonpolar and semipolar structures. Because of this, a strong carrier injection nonuniformity observed in c-plane LDs, causes the threshold current increase when number of QWs is >;2. This effect is not observed in semipolar LDs because the carrier transport rate is faster than the capture rate.

We present the design and the performance of mid-infrared distributed feedback quantum cascade lasers made of strain-balanced GaxIn1-xAs/AlyIn1-yAs material on InP substrates for wavelength near 5 μm. By changing the grating period within one wafer, we demonstrated wide wavelength coverage of 325 and 282 cm-1 (16.3% and 14.1% of the center wavelength) under room temperature pulsed and continuous wave (CW) operation, respectively. The variation of pulsed and CW laser performance as a function of wavelength detuning from the gain peak was studied and correlated to the amplified spontaneous emission spectra. We conclude that a slight positive detuning within 5% of the center wavelength favors CW performance especially for high-temperature operation.