Whispering gallery mode resonators and non-linear generation of THz radiation

Whispering gallery modes (WGM) are confined by total internal reflection at the periphery of a resonator featuring a circular section. We develop micro-cylinder resonators which combine key assets for the realization of a WGM microlaser. Our principal objective is the realization of a compact and innovative THz source, using a non-linear frequency difference between to WGM lasing in the near infrared.

Whispering gallery modes in a micropillar resonator

Intensity map of a WGM supported by a pillar resonator

A micropillar cavity, which consists of a GaAs spacer sandwiched between two AlAs/GaAs Bragg mirrors, is well known to support Fabry-Perrot modes. In 2007, we have discovered that the periphery of the central GaAs layer also supports high Q-factor whispering gallery modes (WGM). These modes, confined by total internal reflection, have been extensively studied in suspended GaAs microdisks supported by a pedestal with a smaller diameter. Interestingly, the pillar geometry features several advantages: the larger pedestal improves the heat evacuation and the pillar geometry is more favourable to the efficient injection of electrical charges in the active layer. These are key assets for the operation of a WGM laser that may find application in the generation of THz radiation (see below).

> to learn more:
Nowicki-Bringuier et al., Optics Express 15, 17291 (2007)
Jaffrennou et al., Appl. Phys. Lett. 96, 071103 (2010)

Non-linear generation of THz radiation

In 2008, we have shown theoretically that a GaAs WGM micropillar resonator can be used to generate THz radiation (collaboration with the ‘Matériaux et Phénomènes Quantiques’ lab., 1 petent). The idea is to generate THz via non-linear frequency difference between two WGM lasing in the near infrared. The conversion is realized thanks to the high X(2) coefficient of GaAs and thanks to a quasi phase matching associated with the circular geometry (it leads to an effective periodic inversion of the non-linear coefficient). Moreover, it is possible to implement an electrical pumping of the near infrared lasing modes, opening the way for the realization of a compact and innovative THz source, which could be moreover operated at room temperature.

> to learn more:
A. Andronico et al., Opt. Lett. 33, 2416 (2008)
Patent : INPI #: 08 53939 du 13/06/2008

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