Low-divergence single-mode terahertz quantum cascade laser

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The operation of quantum cascade lasers has to date been demonstrated over a broad frequency range in the terahertz spectrum (from 4.4 THz to 1.2 THz)1,2,3. Most potential applications of terahertz quantum cascade lasers require a source that has an excellent spatial and spectral control of the radiated emission4,5,6,7. Here, we present a distributed feedback design of a double-metal waveguide quantum cascade laser8,9,10 that features a grating resonant with the third-order Bragg condition. We show that an improvement of the extraction efficiency results in control of the laser emission wavelength and enhanced output power. Moreover, the grating can act as an array of phased linear sources, reshaping the typical wide and patterned far-field of double-metal waveguides into a narrow beam of 10° divergence.

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Figure 1: Vector diagram for a third-order DFB in the wave vector space k.
Figure 2: Finite-element simulations of the third-order DFB waveguide.
Figure 3: Light emission characteristics of typical third-order DFB devices.
Figure 4: Far-field measurements.
Figure 5: Beam pattern for all the devices in which a fundamental lateral mode propagates in the waveguide.


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This work was supported by the Swiss National Foundation under the NCCR project Quantum Photonics. The authors thank A. Bismuto for support in the processing of the devices, J. Lloyd-Hughes for careful reading of the manuscript and Y. Chassagneux and F. Castellano for fruitful discussions.

Author information

M.I.A. carried out the modelling of the structures, fabricated the samples, performed the measurements and wrote the manuscript. M.B. and M.F. conducted MBE growth of the samples. G.S. contributed to data interpretation and experimental work. The idea was developed by J.F., and all the work has been done under his supervision.

Correspondence to M. I. Amanti.

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Amanti, M., Fischer, M., Scalari, G. et al. Low-divergence single-mode terahertz quantum cascade laser. Nature Photon 3, 586–590 (2009) doi:10.1038/nphoton.2009.168

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