Single-mode laser action in quantum cascade lasers with spiral-shaped chaotic resonators

Ross Audet,Mikhail A Belkin,Gloria Höfler,Kai Lin,Evgenii E Narimanov,Jintian Zhu,Federico Capasso,Jonathan A Fan,David Bour,Benjamin G Lee,Scott Corzine

doi:10.1063/1.2784290

Abstract

The authors have fabricated and characterized quantum cascade lasers with spiral-shaped microresonators. The lasers operate in pulsed mode at room temperature with peak optical power greater than 20mW and in continuous wave at temperatures up to 125K. They exhibit single-mode emission in both pulsed mode and continuous wave operation, with a 30dB side-mode suppression ratio at injection currents well above threshold. Subthreshold spectral measurements indicate that the spiral cavities support whispering-gallery-like modes. Single-mode lasing occurs on one of these modes. Far-field profiles reveal enhanced directionality compared to microdisk lasers.

Highlights

The power and directionality of microcylinder quantum cascade lasers can be improved by orders of magnitude by deforming the cavities to support “bow-tie modes.”[1]. Spiral-shaped cavities with “notch” discontinuitiessee Fig. 1͔ have been examined as a means of achieving high-power directional emission from optically pumped polymer lasers[2] and electrically pumped InGaN multiple-quantum-well[3] lasers
Light in WG-like modes is outcoupled in these structures by diffraction at the spiral notch.[4]
The active region of our QCLs consists of 30 stages of a “three-quantum-well” active region design[5] with target wavelength of 8 ␮m, grown by metal organic vapor phase epitaxy.[6]

Summary

Introduction

The power and directionality of microcylinder quantum cascade lasers can be improved by orders of magnitude by deforming the cavities to support “bow-tie modes.”[1] Spiral-shaped cavities with “notch” discontinuitiessee Fig. 1͔ have been examined as a means of achieving high-power directional emission from optically pumped polymer lasers[2] and electrically pumped InGaN multiple-quantum-well[3] lasers. These devices exhibit high-power emission and a strong tendency toward single-mode operation over a wide range of injection currents. Emission in the midinfrared permits a smaller ratio of cavity size to mode wavelength and a concomitant reduction of scattering due to surface roughness compared to previously reported spiral-shaped lasers emitting at visible wavelengths.

Results

Conclusion