λ ∼ 3.36   μ m room temperature InGaAs/AlAs(Sb) quantum cascade lasers with third order distributed feedback grating

Abstract

We report on the development of strain compensated InGaAs/AlAs(Sb) quantum cascade lasers, incorporating a buried third order distributed feedback grating. Single mode operation with a side mode suppression ratio of ∼30 dB has been achieved in the wavelength range of 3.358–3.380 μm for temperatures between 270 and 360 K. The threefold increase in grating pitch size, compared with a first order grating, allows conventional photolithographic techniques to be used for single mode laser fabrication.

Quantum Cascade Laser With Unilateral Grating

“…Features of this size are too small to be defined using ordinary photolithographic techniques, thus it has to be done with electron beam lithography [5]. By contrast, in a third order grating [6] the size of these features is increased to 750-900 nm allowing them to be defined using photolithography. However, the downside of using higher order grating is the reduction of the coupling coefficient κ that defines how strongly the optical mode is coupled to the grating [7].…”