| Popis: |
We present results of comprehensive investigations of the intensity noise of continuous wave (CW) operated quantum cascade lasers (QCLs) under various operation conditions. These experiments are performed with the aim to measure and understand the intensity noise of QCLs, and furthermore to explore the potential to generate non-classical light, i.e. squeezed states of light with sub-shot intensity noise with these new devices. First, we measure the relative intensity noise (RIN) and find that the relative intensity noise behaviour of QCLs is different from that of bipolar edge emitting lasers and Vertical-Cavity Surface-Emitting Laser (VCSELs). These observations are explained by a semi-classical noise description in which the particular level scheme of the QCLs is incorporated via an effective cascaded three-level model. Second, we compare this intensity noise with respect to the shot-noise level in order to explore the possibility of generation of squeezed states of light in the mid-infrared spectral domain with QCLs. In our first experiments we find only an intensity noise 2 dB above the shot noise level. Finally, these experimental results, the possible origin of the observed non-successful sub-shot noise generation, as well as possibilities for future trends, applications and the limitations of these non-classical states of light with respect to sensing and spectroscopic applications are discussed. |
