Mid-infrared (λ=3.25 μm) broadened-waveguide diode lasers with active regions consisting of 5 type-II “W” quantum wells operated in continuous-wave (cw) mode up to 195 K. At 78 K, the threshold current density was 63 A/cm2, and up to 140 mW of cw output power was generated. A second structure with ten quantum wells operated up to 310 K in pulsed mode.

Optically pumped type-II W lasers emitting in the mid-infrared exhibited continuous-wave (cw) operating temperatures of 290 K at $\text{λ=3.0\hspace{0.05em}μ}\mathrm{m}$ and 210 K at $\text{λ=6.1\hspace{0.05em}μ}\mathrm{m}.$ Maximum cw output powers for 78 K were 260 mW at $\text{λ=3.1\hspace{0.05em}μ}\mathrm{m}$ and nearly 50 mW at $\text{λ=5.4\hspace{0.05em}μ}\mathrm{m}.$ These high maximum temperatures were achieved through the use of a diamond-pressure-bonding technique for heat sinking the semiconductor lasers. The thermal bond, which is accomplished through pressure alone, permits topside optical pumping through the diamond at wavelengths that would be absorbed by the substrate.

This research examines the influence of parents on students’ studying the STEM disciplines and entering STEM careers. Cases of two graduate students (one female, one male) and one undergraduate student (male) are featured. The first two students in the convenience sample are biology and physics majors in a STEM teacher education programme; the third is enrolled in computer science. The narrative inquiry research method is used to elucidate the students’ academic trajectories. Incidents of circumstantial and planned parent curriculum making surfaced when the data was serially interpreted. Other themes included: (1) relationships between (student) learners and (teacher) parents, (2) invitations to inquiry, (3) modes of inquiry, (4) the improbability of certainty, and (5) changed narratives = changed lives. While policy briefs provide sweeping statements about parents’ positive effects on their children, narrative inquiries such as this one illuminate parents’ inquiry moves within home environments. These actions became retrospectively revealed in their adult children’s lived narratives. Nurtured by their mothers and/or fathers, students enter STEM disciplines and STEM-related careers through multiple pathways in addition to the anticipated pipeline.

We report measurements of room-temperature mean free paths of long-lived THz acoustic phonons in wurtzite GaN. Longitudinal phonon wave packets are excited and probed by femtosecond laser pulses in two InGaN-GaN multiple quantum well structures separated by a GaN layer. By measuring the temperature dependence of the phonon attenuation in the range 80–300 K we isolate the intrinsic phonon mean free path at 300 K which is found to be 5.3 and 3.5 μm at 1.06 and 1.43 THz, respectively. The measurements are found to be in good agreement with ab initio calculations which show that the main channel of the acoustic phonon decay is a three-phonon scattering process involving the acoustic phonon and two high-frequency optical phonons. Our results indicate that the contribution of low-THz acoustic phonons to thermal transport in GaN is relatively smaller than in Si; thus finite size effects are expected to be less important in GaN.

The purpose of this work is to explore materials for midinfrared detectors that can operate at room temperature. Shorter-period $\mathrm{In}\mathrm{As}∕\mathrm{Ga}\mathrm{Sb}$ superlattices (SLs) have larger intervalance band separations, which are beneficial for reducing Auger recombination and tunneling current, thus making room temperature operation possible. To test these possibilities, several short-period SLs ranging from $50\text{to}11\mathrm{\AA }$ were grown and their morphological properties were carefully monitored by transmission electron microscopy. The effect of structural degradation caused by the period reduction on the optical properties was studied using low-temperature photoluminescence (PL). The samples with larger periods $(50–32\mathrm{\AA })$ showed excellent structural qualities and produced narrow full width at half maximum (FWHM) of the PL peak $\left(5\mathrm{meV}\right)$ . As the period approached $24\mathrm{\AA }$ , slight layer thickness undulations within the SLs were observed and these undulations intensified as the period further reduced to $17\mathrm{\AA }$ . These structural degradations strongly influence optical properties causing significant broadening in the FWHM and higher residual carrier concentration in the shorter-period SLs. With slower growth rates, samples with periods as thin as $19\mathrm{\AA }$ were grown without significant layer undulations.