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Scanning electron microscope pictures of a coupled square ring resonator laser. (a) shows an exemplary device with a square ring resonator coupled to a RWG laser, (b) a closeup of the edges of the square ring, and (c) a cross section of the wide RWG.
Optoelectronic output characteristics of a device with a wide square ring resonator, which is coupled to a 1 mm long and wide RWG. The threshold current shifts from 1.4 A at 80 K up to 1.5 A at 220 K. Output powers of about 80 mW are observed at 80 K.
Emission spectra taken at different temperatures at a drive current of 1.8 A. The inset shows the shift in the wavelength in dependence of the heat sink temperature from 9.04 to . The value of 0.40 nm/K is comparable to that observed for QCL-DFB devices with a surface grating.
High resolution spectrum recorded at 140 K with a drive current of 1.8 A. A SMSR of 22 dB can be obtained. The adjacent modes with a FSR of 51 nm can also be seen in the spectrum. The inset depicts the SMSR in dependence of the wavelength. Stable single mode emission with SMSR between 20 and 26 dB can be observed over a temperature range from 80 up to 220 K.
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