Small-divergence semiconductor lasers by plasmonic collimation

Abstract

Surface plasmons offer the exciting possibility of improving the functionality of optical devices through the subwavelength manipulation of light. We show that surface plasmons can be used to shape the beams of edge-emitting semiconductor lasers and greatly reduce their large intrinsic beam divergence. Using quantum cascade lasers as a model system, we show that by defining a metallic subwavelength slit and a grating on their facet, a small beam divergence in the laser polarization direction can be achieved. Divergence angles as small as 2.48 8 8 8 8 are obtained, representing a reduction in beam spread by a factor of 25 compared with the original 9.9-mm-wavelength laser used. Despite having a patterned facet, our collimated lasers do not suffer significant reductions in output power ( 100 mW at room temperature). Plasmonic collimation provides a means of efficiently coupling the output of a variety of lasers into optical fibres and waveguides, or to collimate them for applications such as free-space communications, ranging and metrology.

Directional emission and universal far-field behavior from semiconductor lasers with limaçon-shaped microcavity

“…The measured divergence is also similar to the one reported for rational caustic resonator 10 ͑ϳ35°͒ and that of Fabry-Pérot type ridge laser ͑ϳ40°͒. 15 Very good agreement between the calculated and the measured far-field profiles was also observed with different from 0.4. We note, however, for larger than 0.5, the geometry of the microcavity is such that WGMs are not supported anymore in the cavity.…”

“…15. The experimental results for a device with an optimal ͑in terms of the far-field divergence angle͒ deformation = 0.40 are shown in Fig.…”

Plasmonic beaming and active control over fluorescent emission

“…In previous studies on beaming of external optical beams [10][11][12][13] , the goal was to obtain the highest possible throughput of incident source light through an aperture, while maintaining desired beaming properties. Here, the aperture serves as a nanoscale optical cavity that can be engineered to efficiently direct the emission of emitters placed inside the cavity.…”

“…The importance of the development of such antenna structures cannot be underestimated as fluorescence processes have a central role in many important applications, including optical spectroscopy techniques, biodetection, photochemistry and lighting. In parallel with the studies on radiative decay engineering with antennas, there is a growing body of work on shaping optical beams (for example, from a light-emitting diode or laser) with the use of patterned metal or dielectric films [10][11][12][13] . This line of research is aimed at realizing desirable beam properties without the use of bulky optical components.…”

Specialized directional beaming through a metalens and a typical application

“…One of the typical works is the presentation regard ing the control of beaming through the subwavelength metallic slits reported by Yu et al in Ref. [16][17][18]. In their discussion, they confirmed that convergence and diver gence of the beaming after the slits are determined by the relationship between the wave vector k SP and item of 2π/Λ, where Λ is the period of the corrugated structure on metal film, as shown in Figure 1A-C.…”