Quantum Cascade Lasers (QCLs) are semiconductor devices that, currently, have been observed to emit radiation from ~ 2.6 μm to 250 μm (1 to 100 terahertz range of frequencies.) They have established themselves as the laser of choice for spectroscopic gas sensing in the mid-wavelength infrared (3-8 μm) and long-wavelength infrared (8-15 μm) region. In the 4-12 μm wavelength region, the highest performing QCL devices, in terms of wall-plug efficiency and continuous wave operation, are indium phosphide (InP) based. The ultimate goal is to incorporate this InP-based QCL technology to silicon (Si) substrate since most opto-electronics are Si-based. The main building blocks required for practical QCL-on-Si integrated platforms will be covered in this work. InP is lattice-mismatched to gallium arsenide (GaAs), even though both are III-V compound semiconductor materials. The first room temperature operation of QCL grown on a lattice-mismatched GaAs substrate with metamorphic buffer (M-buffer) is discussed in this thesis. The QCL structure’s strain-balanced active region was made up of 40-stages of alternating barriers (Al0.78In0.22As) and wells (In0.73Ga0.27As) and an all-InP, 8 μm-thick waveguide. A small sample of 2 cm2 size was taken from a 6-inch wafer and processed into ridge-waveguide chips 3 mm x 30 μm in size. Lateral current injection scheme was utilized due to an insulating M-buffer layer. Preliminary reliability testing up to 200 minutes of runtime showed no sign of power degradation. Laser chips with high reflection (HR) coating showed optical power over 200 mW of total peak power at cryogenic temperature (78 K), with lasing seen up to 230 K. In this temperature range, the measured characteristic temperatures of T0 ≈ 460 K and T1 ≈ 210 K describes the temperature dependence for threshold current and slope efficiency. Adding a partial HR coating (56%) on the front facet extended the lasing range above room temperature (303 K). This thesis will also discuss the preliminary cryogenic temperature result of the first InP-based QCL grown on lattice-mismatched silicon (Si) substrate.
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Master of Science (M.S.)
College of Optics and Photonics
Optics and Photonics
Optics and Photonics
Length of Campus-only Access
Masters Thesis (Open Access)
Go, Rowel, "Room Temperature Operation of Quantum Cascade Lasers Monolithically Integrated Onto a Lattice-Mismatched Substrate" (2018). Electronic Theses and Dissertations. 6430.