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Electronic anti-Stokes–Raman emission in quantum-cascade lasers
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View: Figures


Image of FIG. 1.
FIG. 1.

(a) and (b) Conduction-band diagrams of the nonlinear (a) and pump (b) regions, respectively, in Wafer D3015. The barrier/well widths of each of the 26 periods of the nonlinear stack, henceforth expressed in nanometers, are , where the wells are shown in bold face, and the barriers in plain face. The underlined layers are doped to . The optical dipole matrix elements involved in the AS–Raman transition are and . The pump laser is a conventional 20-stage QC stack emitting at . (c) and (d) Diagram of the conduction band of the nonlinear region (c) and pump region (d), respectively, in Wafer D2924. The pump is a conventional 30-period QC-laser emitting at . The layer thicknesses of each of the 30 periods comprised in the nonlinear stack are , following the same notation as above. The doping concentration in the underlined wells/barriers is . The optical dipole matrix elements and are estimated to be and , respectively. In all cases, the InGaAs wells and AlInAs barriers are grown lattice matched to the InP substrate. The moduli squared of the relevant wavefunctions are also shown. In (a) and (c), the black arrows indicate the Raman transition and the levels involved are numbered. In (b) and (d), the letters U and L indicate the upper and lower pump laser levels, respectively. The ground level of the injector is labeled as g in all four plots.

Image of FIG. 2.
FIG. 2.

Normalized mode intensity profile and profile of the real part of the refractive index in the reverse growth direction (the substrate is located on the right-hand in the graphs) for both AS and pump fundamental modes in Wafer D3015.

Image of FIG. 3.
FIG. 3.

(a) Short-wavelength emission spectra of D3015 above laser threshold. Peaks attributed to AS–Raman emission and incoherent upconversion can be distinguished. The dip observed around is characteristic of absorption. The inset shows the spectrum of the pump laser measured at a heat sink temperature of and peak current. (b) Short-wavelength luminescence spectra, above threshold, of D2924 measured near liquid-helium temperatures . The main peak at is attributed to AS–Raman emission. The inset shows the pump spectrum measured at and a peak current of .

Image of FIG. 4.
FIG. 4.

LIV characteristics of the lasers of wafers D3015 (solid lines) and D2924 (dashed lines). These measurements were carried out at liquid-nitrogen temperatures.


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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Electronic anti-Stokes–Raman emission in quantum-cascade lasers