DOC PREVIEW
LECTURE

This preview shows page 1 out of 3 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 3 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 3 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

tocRoom-Temperature Continuous-Wave Quantum Cascade Lasers Grown byZhijun Liu, Daniel Wasserman, Scott S. Howard, Anthony J. HoffmaI. I NTRODUCTIONFig.€1. (a) Portion of the conduction band diagram and the modulII. L ASER D ESIGN AND F ABRICATIONIII. L ASER C HARACTERIZATIONFig. 2. (a) CW light current curves of an HR-coated, 8- $\mu{\hbFig.€3. Measured pulsed threshold current density versus reciproFig. 4. Net modal gain ${G} _{M}$ as a function of the current dFig.€5. Calculated modal gain coefficient as a function of tempeIV. C ONCLUSIONJ. Faist, F. Capasso, D. L. Sivco, C. Sirtori, A. L. Hutchinson,M. Beck, D. Hofstetter, T. Aellen, J. Faist, U. Oesterle, M. IleJ. S. Yu, S. Slivken, A. Evans, L. Doris, and M. Razeghi, High-pA. Evans, J. S. Yu, S. Slivken, and M. Razeghi, Continuous-wave S. Blaser, D. A. Yarekha, L. Hvozdara, Y. Bonetti, A. Muller, M.J. S. Yu, A. Evans, S. Slivken, S. R. Darvish, and M. Razeghi, SJ. S. Yu, S. R. Darvish, A. Evans, J. Nguyen, S. Slivken, and M.V. Moreau, A. B. Krysa, M. Bahriz, L. R. Wilson, R. Colombelli, J. S. Roberts, R. P. Green, L. R. Wilson, E. A. Zibik, D. G. RevM. Troccoli, S. Corzine, D. Bour, J. Zhu, O. Assayag, L. Diehl, L. Diehl, D. Bour, S. Corzine, J. Zhu, G. Hofler, B. G. Lee, C.IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 12, JUNE 15, 2006 1347Room-Temperature Continuous-Wave QuantumCascade Lasers Grown by MOCVD WithoutLateral RegrowthZhijun Liu, Daniel Wasserman, Scott S. Howard, Anthony J. Hoffman, Claire F. Gmachl, Senior Member, IEEE,Xiaojun Wang, Tawee Tanbun-Ek, Liwei Cheng, and Fow-Sen Choa, Senior Member, IEEEAbstract—We report on room-temperature continuous-wave(CW) operation of8 2m quantum cascade lasers grownby metal–organic chemical vapor deposition without lateral re-growth. The lasers have been processed as double-channel ridgewaveguides with thick electroplated gold. CW output power of5.3 mW is measured at 300 K with a threshold current density of2.63 kAcm2. The measured gain at room temperature is close tothe theoretical design, which enables the lasers to overcome therelatively high waveguide loss.Index Terms—Continuous-wave (CW) lasers, midinfrared,quantum cascade (QC) lasers, semiconductor lasers.I. INTRODUCTIONQUANTUM cascade (QC) lasers are promising and in-fluential midinfrared light sources with potential forapplications as varied as chemical sensing, wirelesscommunication, and counter-measures. Since their first demon-stration in 1994 [1], constant and significant performanceimprovements have been made for QC lasers through im-proved laser design, material growth, and packaging. Up tonow, room-temperature continuous-wave (CW) operation, animportant milestone for compact noncryogenic laser sources,has been demonstrated for QC lasers grown by solid sourcemolecular beam epitaxy (MBE) or gas-source MBE at wave-lengths of9.1 and 4–6 m [2]–[7]. Metal–organic chemicalvapor deposition (MOCVD) has recently attracted researchinterest because it is a technology preferred by industry andis promising for the commercialization of QC lasers [8].MOCVD has been reported as a high-performance QC lasergrowth technique, first with low threshold pulsed operation[9], and very recently, room-temperature CW operation of anMOCVD-grown7.2- m QC laser and an MOCVD-grown5.1- m strained QC laser using a buried heterostructuredesign [10], [11]. In this letter, we report on an MOCVD-grownroom-temperature CW QC laser atm without buriedManuscript received February 22, 2006; revised April 7, 2006. This work wassupported in part by the Defense Advanced Research Projects Agency (DARPA)L-PAS.Z. Liu, D. Wasserman, S. S. Howard, A. J. Hoffman, and C. F. Gmachl arewith the Department of Electrical Engineering and the Princeton Institute forthe Science and Technology of Materials, Princeton University, Princeton, NJ08544 USA (e-mail: [email protected]).X. Wang and T. Tanbun-Ek are with AdTech Optics, City of Industry, CA91748 USA.L. Cheng and F.-S. Choa are with the Department of Computer Science andElectrical Engineering, University of Maryland, Baltimore, MD 21250 USA.Digital Object Identifier 10.1109/LPT.2006.877006Fig. 1. (a) Portion of the conduction band diagram and the moduli squared ofthe relevant wave functions of a8.2-m QC laser with a four quantum-wellactive region based on a two phonon resonance. An electric field of 51 kV/cmis applied. The arrow indicates the laser transition. (b) Intensity profile of thefundamental mode, layer structure, and profile of the real part of the refractiveindex of the dielectric waveguide used.heterostructure. The laser is processed as a double-channelridge waveguide with thick electroplated gold on top, allowingthe omission of the more complex lateral InP regrowth step.II. LASER DESIGN AND FABRICATIONThe laser active region is based on a two-phononresonance design. The layer sequence (in ångströms)of one period of active region and injector is44/18/9/57/11/54/12/45/25/34/14/33/13/32/15/31/19/29/23/27/25/27, where InAl As barrier layers are in bold,InGa As well layers are in roman, and the n-doped(cm ) layers are underlined. The electron energyband diagram is shown in Fig. 1(a). The energy of the lasertransition between levels 4 and 3 is designed as 154 meV,1041-1135/$20.00 © 2006 IEEE1348 IEEE PHOTONICS TECHNOLOGY LETTERS, VOL. 18, NO. 12, JUNE 15, 2006and levels 1, 2, and 3 are each separated by about one opticalphonon energy. The relatively large energy separation betweenlevel 3 and the ground state of the next down stream injector(147 meV) is intended to suppress the thermal back fillingeffect. The lifetime of the upper laser level is designed asps, and that of lower laser level is ps. Thedipole matrix elementis 1.8 nm.Thirty-five periods are used as the active core and sand-wiched between two 0.5-m-thick n-doped ( cm )InGa As layers. The upper cladding layers consistsof 2-m-thick n-doped (1 cm ) InP, followed by a1-m-thick n -doped ( cm ) InP cap layer. Thecalculated intensity profile of the fundamental mode is shownin Fig. 1(b). The waveguide lossis calculated as 6.6 cm ,and the confinement factoris 0.67.The double-channel ridge waveguide lasers were fabricatedby conventional wet-chemical etching. A 0.3-m-thick Si Nlayer was deposited for side-wall insulation. After evaporationof Ti–Au (30/300 nm) for the top contact, am-thickgold layer was electroplated around the laser ridge for ef-ficient heat transfer. To facilitate cleaving, small gaps wereleft in the


LECTURE

Download LECTURE
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view LECTURE and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view LECTURE 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?