Abstract
Power scaling in broad area quantum cascade laser (QCL) usually leads to the deterioration of the beam quality with an emission of multiple lobes far-field pattern. In this letter, we demonstrate a tapered QCL array integrated with Talbot cavity at one side of the array. Fundamental supermode operation is achieved in the arrays with taper straight-end connected to the Talbot cavity. Lateral far-field of the fundamental supermode shows a near diffraction limited beam divergence of 2.7°. The output power of a five-element array is about three times as high as a single-ridge laser with an emission wavelength of around 4.8 μm. However, arrays with the taper-end connected to the Talbot cavity always show a high-order supermode operation whatever Talbot cavity length is.
Highlights
Quantum cascade laser (QCL), invented in 1994, has been one of the most important light sources in mid- and far-infrared for its wavelength flexibility and portability [1,2,3]
Single-lobe emission is obtained in the past with the methods such as photonic crystal distributed-feedback (PCDFB) QCLs, angled cavity QCLs, master-oscillator power-amplifier QCLs, and broad area QCLs via external feedback mechanisms [9,10,11,12]
Mj sin M þ ω2 where j is the order of supermode, M is the numbers of array elements, ω is the waist of the Gauss beam in each element, and xm is the central location of each element
Summary
Quantum cascade laser (QCL), invented in 1994, has been one of the most important light sources in mid- and far-infrared for its wavelength flexibility and portability [1,2,3]. Popular applications of QCLs have covered many areas such as free space optical communication and directed infrared countermeasure (DRICM), trace chemical sensing of explosives, toxins, pollutants, and medical testing [4,5,6,7]. High power QCLs can be obtained by broadening the width of active region area. A simple broadening of the ridge without waveguide engineering design or external optics will deteriorate the beam quality of QCLs with an emission of multiple lobes far-field pattern [8]. Single-lobe emission is obtained in the past with the methods such as photonic crystal distributed-feedback (PCDFB) QCLs, angled cavity QCLs, master-oscillator power-amplifier QCLs, and broad area QCLs via external feedback mechanisms [9,10,11,12]. Phase-locked arrays have been popular approaches to keep wide ridge QCL emitting with coherent narrow beam patterns
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