Tapered QC lasers reduce beam divergence

Jan. 1, 2008
Although mid- to far-infrared quantum-cascade (QC) lasers are ideal for gas sensing, free-space optical communications, and imaging, their high beam divergence (typically about 48º for ridge-waveguide devices) can be a limiting factor for resolution and efficiency.

Although mid- to far-infrared quantum-cascade (QC) lasers are ideal for gas sensing, free-space optical communications, and imaging, their high beam divergence (typically about 48º for ridge-waveguide devices) can be a limiting factor for resolution and efficiency. To significantly reduce this divergence, researchers at the Universität Würzburg (Würzburg, Germany) created lasers with an index-guided tapered gain section using a unique processing method.

Click here to enlarge image

In the growth process, 35 active periods on an indium phosphide (InP) substrate are embedded in tapered structures in an indium gallium arsenide waveguide core facing the substrate and adjacent to a 2-µm-thick InP top cladding. This approach differs not in the QC growth stage, but in the processing of the grown structure: instead of just evaporating a tapered contact on the grown structure (as in the typical gain-guided approach for semiconductor diode lasers), the researchers completely etch through the grown layers leaving a tapered-shaped device. Because they etch through the whole active region and achieve a semiconductor/air interface, current spreading does not take place and divergence is minimized. The 200 mW tapered QC lasers have a horizontal beam divergence of only 6.6º in the single-lobe far field at a wavelength of approximately 8.9 µm. Contact Julia Semmel at [email protected].

Sponsored Recommendations

Achromatic Lenses: High-Quality Custom Optics

March 13, 2025
Ensure clarity and accuracy in your optics systems with Lacroix’s achromatic lenses. Explore how our custom solutions minimize chromatic aberration for perfect results.

Manufacturing Considerations for Tolerancing Aspheres

March 13, 2025
Understand the critical factors in manufacturing aspheres and how Lacroix Optics ensures precise tolerancing in every optical component.

Explore Our Videos: Insights into Precision Optics

March 13, 2025
Get an inside look at Lacroix Optics with our collection of informative videos showcasing our capabilities, innovations, and processes.

Optical Assemblies: Reliable and Precise Solutions

March 13, 2025
Ensure your optical system works seamlessly with Lacroix Optics' custom optical assemblies. Discover the precision and reliability we bring to every project.

Voice your opinion!

To join the conversation, and become an exclusive member of Laser Focus World, create an account today!