We demonstrate spectrally single-mode, low-divergence surface-emission from photonic-crystal quantum cascade lasers operating in the mid-infrared spectral range (λ～7.2μm). The photonic-crystal resonator is defined by the sole top metallization. No semiconductor etch is employed. The effective index contrast is induced by the different profiles of surface plasmon and air-confined modes. Numerical electromagnetic simulations show that the resonator Q-factor depends strongly on the r/a ratio. The devices - which operate up to 220 K - exhibit single mode emission with a side mode suppression ratio ≥20/25dB. The far-field emission pattern is doughnut-shaped, with a full divergence angle of ～12 degrees.
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机译：我们证明了在中红外光谱范围（λ〜7.2μm）中的光子晶体量子级联激光器的光谱单模，低发散的表面发射。光子晶体谐振器由鞋底金属化限定。没有采用半导体蚀刻。有效指数对比度由表面等离子体和空气限制模式的不同轮廓引起。数值电磁模拟表明，谐振器Q系数强烈依赖于R / A比率。该装置 - 操作高达220 k - 展示单模发射，侧面模式抑制比≥20/ 25dB。远场排放图案是甜甜圈形的，具有〜12度的全部分角。
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