2005 Conference on Lasers and Electro-Optics Europe

Recent advances in QCL for optoelectronics

J. Faist, University of Neuchatel

The quantum cascade laser based on intersubband transitions in quantum wells is now maturing as atechnological device for both physics and applications. It allows design of lasers of widely differentwavelengths from the same heterostructure material. Recently, a strong improvement of the laser operatingperformances has enabled the room tempeature operation of continuous wave, single mode, lasers around awavelength of 5.4 m. As shown in Fig. la), these distributed feedback lasers operate with 3-5mW ofoutput power and a currents well below IA[l].Distributed feedback quantum cascade lasers have maximum tuning ranges around 5-10cml, obtained bychanging the temperature of the device either by external heating or by simply ramping the drive current.Although this is enough for most gas spectroscopy, it is clearly not sufficient for the spectroscopy ofmulticomponent gases or liquids and solids. To this aim, a quantum cascade laser using an active regionbased on a bound-to-continuum transition with a broad gain spectrum is operated in continuous wave in anextemal cavity. This device exhibits a continuous single mode tuning range of 170cm', centered at1900cm-' with an optical power of lOmW [2].

a) J,kAlcm b) B , 2500 0.4 0.8 1.2 1.6 2.0 2.4 10K

~~~~~~~~~~~~~~~~~~~~~~~~~200c ~~~~~~~~20K

O~~~~~~~~c ~~~~~~~1504 0

>~1 E Cuet A

Fig.~~~~~~~~1a)Cniuu'aelgtitniyvrusdiecretfrasnlprqec

/1~~~~~~~ 2~~~40K 50

/ 0.c~~~~~00 .4 002( 0 0 7 45K 20 0.2 0.4 0. 0.8 100 04 08 12

I, A Current [AI

Fig. I a) Continuous wave light intensity versus drive current for a single frequencydevice operating at 1840cm'1. b) InP-based terahertz quantum cascade laser.

A other fascinating new development has been the realization of terahertz QC lasers. Devices basedbased on GaAs have reached now operating temperatures higher than lOOK. However, devices based onInGaAs/AlInAs lattice-matched on InP should have the advantage of a stronger optical matrix element anda lower optical phonon scattering rate and therefore should enable operation at higher temperatures. Asshown in Fig lb), we have demonstrated the first of such devices that operate at a wavelength of 80 m,corresponding to 3.75 Thz [3].

References:

[11 S. Blaser, D. Yarekha, L. Hvodzara, J. Faist, E. Gini. Appl Phys. Lett. In print.

[21 R. Maulini, D. Yarekha, M. Giovannini, J. Faist, unpublished

[31 L. Ajili, G. Scalari, M. Giovannini, N. Hoyler, J. Faist, unpublished

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