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(a) and (b): Optical microscope image of a cross section of epi-down mounted on AlN submount μSQCL made of 32 emitters with w = 2 μm, D = 4 μm. (c) Scanning electron microscope image.
Cross-section simulation made with a thermo-electrical model (comsol), with same current density injected. ΔT is the thermal elevation in the active region. It is shown for a broad QCL with w = 8 μm (top), μSQCL made of N = 4, width of w = 2 μm, spacing of D = 4 μm (middle) and μSQCL made of N = 8, width of w = 1 μm, spacing of D = 4 μm (bottom). Peltier is located downward.
Numerical and experimental thermal resistance of μSQCL mounted epi-side down on AlN submount. Plain curves correspond to the simulation: the red curve is the broad QCL, the blue one μSQCL with w = 2 μm, and the green one μSQCL with w = 1 μm. Scatters are the experimental data, with the same corresponding colors. Inset: Thermal resistance ratio between broad QCL and μSQCL (w = 2 μm, D = 4 μm) versus W for AlN submount (blue dashed) and diamond submount (red plain).
Voltage versus current curves of a μSQCL (w = 2 μm, D = 4 μm, N = 8). Dashed curves represent pulsed operation (300 ns/100 kHz) at different Peltier temperature. Plain red curve is a CW measurement at 10 °C. Inset: Rth evaluated at each intersections.
Numerical projection of CW power calculated on broad QCL and μSQCL (w = 2 μm, D = 4 μm) versus the total AR width W, where W = N*w for the μSQCL case. Red and black curves correspond to, respectively, the broad QCL and μSQCL on AlN submount. Pink and blue curves to the broad and μSQCL on diamond submount, respectively. Inset: comparison of experimental P(I) from Ref. 1 (plain) with the numerical model (dashed) at different Peltier temperatures in CW operation.
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