Temperature dependence of 4.1 μm mid-infrared type II “W” interband cascade lasers

Abstract

The thermal properties of 5-stage “W” Interband-Cascade Lasers emitting at 4.1 μm at room temperature (RT) are investigated by measuring the lasing and spontaneous emission properties as a function of temperature and hydrostatic pressure up to 1 GPa. Experiments show that at RT more than 90% of threshold current of these devices is due to non-radiative loss processes. We also find that the threshold current density dependence on temperature can be fitted with a single exponential function over a wide temperature range with a characteristic temperature, T0, of 45 K. The relatively high temperature sensitivity in these devices is attributable to the large non-radiative current contribution coupled with non-pinning of the carrier density above threshold.

The Interband Cascade Laser

“…However, owing to the large electron density already present in the ICL active core, due to carrier rebalancing, it may result from an increase of the hole density above the threshold (i.e., the density does not pin). This conjecture is also consistent with the observation that the spontaneous emission intensity fails to saturate above the threshold [88], although the linewidth broadening factor data discussed in Section 4.11 above provided evidence for pinning [229]. Non-pinning of the carrier concentration and emission intensity above the threshold is also characteristic of type-I mid-IR QW lasers [11,89].…”

“…Its magnitude is anomalous because, in the absence of significant heating, the carrier density in an ideal laser becomes pinned as soon as sufficient gain is generated to overcome the cavity loss at the threshold. Instead, limited measurements of the spontaneous emission above the lasing threshold [88] appear to indicate a continuing increase of the carrier density in the active QWs, although the data do not preclude growing differences in the electron and hole densities. Furthermore, the cavity-length data to be discussed in Section 5.2 imply that most of the efficiency droop results from an increasing internal loss rather decreasing internal efficiency.…”

Electrically widely tunable interband cascade lasers

“…A non-pining of the carrier density above threshold was observed in previous IC lasers particularly at high temperatures. 22 Practically, the non-ideal conditions such as low tunneling efficiency and additional transition states may slow down the lasing process and result in a wavelength shift after lasing. Below, we will present IC lasers with three InAs QW layers in the active region, which exhibited substantial wavelength tuning even for pulsed conditions without heating.…”

Nanoscopically resolved dynamic charge-carrier distribution in operating interband cascade lasers

“…Clearly the subpar performance of the ICL under this study is not limited by fundamental physics and its strong temperature dependence of the lasing threshold current is not intrinsic to ICLs. Lack of carrier clamping in ICLs operating at higher temperature has been reported . As the ICL under study does not lase beyond 248 K, the observed carrier clamping from our SVM measurements may only apply to low temperatures.…”