Room Temperature CW Operation of Short Wavelength Quantum Cascade Lasers Made of Strain Balanced Ga $_{\bm x}$In$_{\bm {1-x}}$ As/Al$_{\bm y}$ In$_{\bm {1-y}}$As Material on InP Substrates

We present our recent development of short wavelength quantum cascade lasers (QCLs) made of strain balanced Ga
$_x$
In
$_{1-x}$
As/Al
$_y$
In
$_{1-y}$
As material on InP substrates. We demonstrate room temperature continuous-wave (CW) lasing of the fundamental lateral mode at four wavelengths of 4.6, 4.0, 3.8, and 3.5 μm. We obtained 60-mW CW output power at 10 °C and 3.55-μm wavelength, which is the shortest CW lasing wavelength demonstrated at room temperature by a QCL, to the best of our knowledge. We also performed a life test on λ = 4.6 μm QCL chips. To date, we have accumulated the life test data for more than 11 000 and 4100 h under two aging conditions, 20 °C and 0.85-A constant current, and 60 °C and 1-A constant current, respectively.