Integration of ridge array and Talbot cavity is an effective method for semiconductor laser optical power amplification. However, it is difficult for such designs to work stably in the fundamental supermode, resulting in the inability to achieve phase locking among the ridge arrays. Here, we report a phase-locked scheme that significantly increases the waveguide loss of high-order supermodes by adjusting the absorption boundary width of the ridge array, making the Talbot devices work stably in the fundamental supermode. Compared with the first-generation devices, the output power of the designed device is increased from 286 mW to 359 mW, and the central brightness is increased by twice. The demonstrated phase-locked high-brightness terahertz (THz) laser sources will have great application potential in THz spectroscopy and imaging.
We have made improvements for QCL in the thermal management to produce high output power. Unlike the previous literature, we use epilayer-down mounting and buried heterostructures to achieve high output power by improving the heat dissipation and reducing the thermal resistance. At 20 K, the continuous wave threshold current density is 110 A·cm-2 and the maximum current density is 210 A·cm−2. The maximum output power is about 250 mW at single facet. The central frequency is approximately ∼4 THz, which matches the energy band design. The thermal simulation shows that, compared with the traditional device, the heat removal performance of the optimized device is significantly improved, and the core temperature is reduced by about 20 K. It improves the heat extraction through epilayer-down mounting and buried heterostructures and leads also to significant lateral heat fluxes. The ways can facilitate the heat extraction in all in-plane directions. In conclusion, this method is beneficial to the development of high continuous wave power, especially for thick active region design. The demonstration of buried heterostructure terahertz quantum cascade lasers for epilayer-down mounting can promote the development of high-power terahertz source in continuous wave.
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