Broadband tunable quantum cascade laser for external cavity

Summary form only given. A homogeneous broad gain bandwidth quantum cascade laser for external cavity is demonstrated. Spectrally homogeneous gain of anticrossed dual-upper state (DAU) design provide wide and stable wavelength tunability with external cavity configuration.Quantum cascade (QC) lasers have become the standard laser light sources for sensing applications in midinfrared region. Distributed feedback (DFB) QC-lasers which allow spectral single-mode emission are the most suitable light sources for applications where high-accuracy is requested. However, narrow wavelength tuning range of the DFB-QC-lasers (-5 cm-1) is a limitation of widespread in sensing applications. External cavity configuration is an alternative approach which allows wide wavelength tuning and various types of QC-gain media for the external cavity are proposed and demonstrated. Most of these are heterogeneous structure (severalwavelength-stack gain media) to extend gain bandwidth of the QC-lasers. Spectrally homogeneous broadband quantum cascade laser was developed and broad tuning was realized with external cavity mode. A unique homogeneous broadband design of QC-laser; anticrossed dual-upper state (DAU) design was employed [1-4] and tuning range of 321 cm-1 (from 6.0 gm to 7.42 gm) in pulsed operation was achieved. Even though the DAU structure is designed to be identical wavelength, its gain bandwidth is compatible to several-wavelength stack gain media. The DAU design also has the unique feature of weak dependence on operating voltage and insensitivity to temperature change [5]. The DAU is promising design for gain media for broadly tunable QC-system.