Opt Quant Electron (2008) 40:197–204 DOI 10.1007/s11082-007-9153-x Effective-mass superlattice as an injector in quantum cascade lasers Mykhailo V. Klymenko · Ivan M. Safonov · Oleksiy V. Shulika · Igor A. Sukhoivanov · Rainer Michalzik Received: 29 June 2007 / Accepted: 16 November 2007 / Published online: 29 November 2007 © Springer Science+Business Media, LLC. 2007 Abstract In this paper, we have developed new design of the injector for quantum cascade structures based on the effective mass superlattice. The transmission spectra of the con- ventional injector and effective-mass injector have been compared. Advantage of the effec- tive-mass injector is more uniform spectrum of pass-band. This feature allows to improve controllability of the quantum cascade laser, to increase stability of its operation and to decrease sensitivity to noise in applied voltage bias. Also, we have computed geometrical parameters for effective-mass injector which is appropriate to provide inverted population in existing quantum-cascade lasers. Such injector should be characterized by 15–25 numbers of layers with widths of layers up to 2 nm. Keywords Quantum cascade laser · Effective mass superlattice · Transmission spectrum · Injector 1 Introduction Quantum cascade lasers (Gmachl et al. 2001) are promising sources for lasing in IR or THz frequency ranges. It has been known that their general principle of operation is based on intersubband transitions (Kazarinov and Suris 1971). At present time, two types of pump- ing are available to provide inverted population in intersubband emitted devices. They are optical pumping (Julien et al. 1995) and injecting (Faist et al. 1995). In the case of injecting, threshold current, dynamic, modulation characteristics and efficiency of quantum cascade M. V. Klymenko (B ) · I. M. Safonov · O. V. Shulika · I. A. Sukhoivanov Lab “Photonics”, Kharkov National University of Radio Electronics, Lenin Ave., 14, Kharkov 61166, Ukraine e-mail: mikhail-klimenko@yandex.ru I. M. Safonov · R. Michalzik Institute of Optoelectronics, Ulm University, Ulm, Germany I. A. Sukhoivanov Departamento de Electronica, FIMEE, University Guanajuato, Guanajuato, Mexico 123