HgCdTe-based quantum cascade lasers operating in the GaAs phonon Reststrahlen band predicted by the balance equation method

Thin active region HgCdTe-based quantum cascade laser with quasi-relativistic dispersion law

HgCdTe is promising as a material to solve a problem of the development of semiconductor sources with an operational frequency range of 6-10 THz due to the small optical phonon energies and electron effective mass. In this study, we calculate the dependence of the metal-metal waveguide characteristics on the number of cascades for the 3-well design HgCdTe-based quantum cascade laser at 8.3 THz. It is shown that four cascades are sufficient for lasing at a lattice temperature of 80 K due to the large gain in the active medium. The results of this study provide a way to simplify the fabrication of thin active region HgCdTe-based quantum cascade lasers for operation in the range of the GaAs phonon Reststrahlen band inaccessible to existing quantum cascade lasers.

Terahertz radiation and the skin: a review

SIGNIFICANCE

Terahertz (THz) radiation has demonstrated a great potential in biomedical applications over the past three decades, mainly due to its non-invasive and label-free nature. Among all biological specimens, skin tissue is an optimal sample for the application of THz-based methods because it allows for overcoming some intrinsic limitations of the technique, such as a small penetration depth (0.1 to 0.3 mm for the skin, on average).

AIM

We summarize the modern research results achieved when THz technology was applied to the skin, considering applications in both imaging/detection and treatment/modulation of the skin constituents.

APPROACH

We perform a review of literature and analyze the recent research achievements in THz applications for skin diagnosis and investigation.

RESULTS

The reviewed results demonstrate the possibilities of THz spectroscopy and imaging, both pulsed and continuous, for diagnosis of skin melanoma and non-melanoma cancer, dysplasia, scars, and diabetic condition, mainly based on the analysis of THz optical properties. The possibility of modulating cell activity and treatment of various diseases by THz-wave exposure is shown as well.

CONCLUSIONS

The rapid development of THz technologies and the obtained research results for skin tissue highlight the potential of THz waves as a research and therapeutic instrument. The perspectives on the use of THz radiation are related to both non-invasive diagnostics and stimulation and control of different processes in a living skin tissue for regeneration and cancer treatment.