Abstract

Near- and far-fields of quantum-cascade lasers emitting in the spectral range near 8 μm have been studied. For all laser samples with a ridge width of 20 and 50 μm, lasing on the fundamental waveguide mode with a divergence of ~50° was observed for all laser samples with a ridge width of 20 and 50 μm along the “fast” axis. Along the “slow” axis, a multimode lasing and a competition between the fundamental and higher waveguide modes, which is manifested for lasers with a ridge width of 50 μm in an increase in the emission divergence from ~10° near the threshold to >50° when the lasing threshold is exceeded by a factor of 2–3. The divergence along the “slow” axis for lasers with ridge width of 22 μm remained invariable in the whole range of pumping currents and equaled ~50°. That there is a substantial contribution from the fundamental mode to the total emission intensity of quantum-cascade lasers, which is apparent from the far-field intensity distribution pattern, cannot be established exclusively on the basis of results obtained in near-field measurements.

中文翻译：

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8μm光谱范围内量子级联激光器的空间发射特性研究

摘要

研究了在近8μm光谱范围内发射的量子级联激光器的近场和远场。对于脊宽度为20和50μm的所有激光样品，在“快速”轴上对脊宽度为20和50μm的所有激光样品观察到基本波导模式的激光发散为〜50°。沿着“慢”轴，多模激射以及基本和较高波导模式之间的竞争，这对于脊宽为50μm的激光器而言，发射散度从接近阈值的〜10°增大到> 50，表现为°超过激光阈值2–3。脊宽度为22μm的激光器沿“慢”轴的发散在整个泵浦电流范围内保持不变，约为50°。