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Current noise and photon noise in quantum cascade lasers Farhan Rana and Rajeev J. Ram

Summary: Current noise and photon noise in quantum cascade lasers
Farhan Rana and Rajeev J. Ram
Research Laboratory for Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139
Received 14 August 2001; published 12 March 2002
A model for the photon noise and the current noise in quantum cascade lasers is presented. It is shown that
compared to diode lasers quantum cascade lasers exhibit much less photon-number squeezing even when the
noise in the drive current is suppressed well below the shot-noise value. The theoretical model presented in this
paper self-consistently accounts for the suppression of the current noise in electron transport in multiple
quantum-well structures due to various electronic correlations. The nature of these electronic correlations is
discussed. Mechanisms that make photon-number squeezing difficult to achieve in quantum cascade lasers are
discussed. Scaling of the laser intensity noise and the current noise with the number of cascaded gain stages is
also described. Direct-current modulation response of quantum cascade lasers is also studied, and it is shown
that contrary to the predictions in the literature of terahertz modulation bandwidth for these lasers, bandwidth
of almost all quantum cascade lasers that have been reported in the literature is limited by the inverse photon
lifetime inside the laser cavity to tens of gigahertz.
DOI: 10.1103/PhysRevB.65.125313 PACS number s : 78.67.De, 72.70. m, 73.21.Fg
Unipolar quantum cascade lasers QCL's utilizing inter-
subband transitions to generate photons have become impor-
tant sources of light in the mid-infrared region


Source: Afshari, Ehsan - School of Electrical and Computer Engineering, Cornell University


Collections: Engineering