Spatially resolved thermoreflectance study of facet temperature in quantum cascade lasers

Abstract

In the present work, we use spatially resolved thermoreflectance (SR TR) to measure temperature distribution over the facet of pulsed operated quantum cascade lasers. The laser beam probes the change in the refractive index caused by current-induced heating of working device. The technique has a spatial resolution of about ~1 µm and temperature resolution better than 1 K. It gives an insight into distribution and relative importance of heat sources within the laser.

Mechanisms and fast kinetics of the catastrophic optical damage (COD) in GaAs‐based diode lasers

“…431 Bugajski et al [125] have used this technique for analyzing different mounting arrangements via an advanced determination of thermal resistances and for the assessment of different etching technologies. The same group also reported facet temperature analysis in quantum cascade devices [123,129]. Hayakawa et al [120][121][122] investigated the impact of device design parameters such as emitter stripe width and waveguide thickness on the facet temperature.…”

“…(3) depends sensitively on the probe wavelength and the inspected material and needs to be determined experimentally for each sample. Epperlein quotes a temperature uncertainty of the technique of 0.5 K [117], while Wawer et al give a value of <1 K [123]. Additional temperature calibration of the reflectance modulation technique has been achieved by using micro-Raman data for the same devices [35,119].…”

“…After the onset of the thermal runaway, a ΔT -increase of 330 K within less than 2 s is found. The high speed of the reflectance modulation technique allowed to take temperature maps at facets [28,71,117,119,120,[123][124][125][126][127][128]. Furthermore, it became possible to monitor even fairly extended devices such as high power diode laser bars, often called 'cm-bars' (because of the total array width of one cm) [126][127][128].…”

Mathematical Models of Heat Flow in Edge-Emitting Semiconductor Lasers

“…The investigations have been inspired by temperature maps obtained by thermoreflectance method (Bugajski et al (2006); Wawer et al (2005)) for p-down mounted devices. These maps suggest the presence of the region of constant temperature in the vicinity of the n-contact.…”

Thermoreflectance spectroscopy—Analysis of thermal processes in semiconductor lasers

“…Thermoreflectance measurements of QCL started in at the Institute of Electron Technology in 2005 and lead to the ability to register temperature distribution over the facet of QCL [116]. In the next papers [117][118][119] different mounting options and device geometries are compared in terms of their influence on the relative increase of the active region temperature.…”