InP-based quantum cascade lasers monolithically integrated onto silicon.

Lasing is reported for ridge-waveguide devices processed from a 40-stage InP-based quantum cascade laser structure grown on a 6-inch silicon substrate with a metamorphic buffer. The structure used in the proof-of-concept experiment had a typical design, including an Al0.78In0.22As/In0.73Ga0.27As strain-balanced composition, with high strain both in quantum wells and barriers relative to InP, and an all-InP waveguide with a total thickness of 8 µm. Devices of size 3 mm x 40 µm, with a high-reflection back facet coating, emitted at 4.35 µm and had a threshold current of approximately 2.2 A at 78 K. Lasing was observed up to 170 K. Compared to earlier demonstrated InP-based quantum cascade lasers monolithically integrated onto GaAs, the same laser structure integrated on silicon had a lower yield and reliability. Surface morphology analysis suggests that both can be significantly improved by reducing strain for the active region layers relative to InP bulk waveguide layers surrounding the laser core.

Room-temperature broadband emission of an InGaAs/GaAs quantum dots laser.

We report the first demonstration to our knowledge of an ultrabroad emission laser using InGaAs/GaAs quantum dots by cycled monolayer deposition. The device exhibits a lasing wavelength coverage of approximately 40 nm at an approximately 1160 nm center wavelength at room temperature. The broadband signature results from the superposition of quantized lasing states from highly inhomogeneous dots.

An economic assessment of Apligraf (Graftskin) for the treatment of hard-to-heal venous leg ulcers.

Several recent advances in wound care may offer promise for the treatment of hard-to-heal venous leg ulcers. One such treatment is Apligraf (Graftskin), a bilayered, living human skin construct. To assess the economic impact of Graftskin, a model was constructed to compare the annual medical costs and cost-effectiveness of treating hard-to-heal venous leg ulcers with Graftskin vs. compression therapy using Unna's boot. A semi-Markov model was used to describe the pattern of ulcer treatment, healing, and recurrence among patients with venous leg ulcers. Patients received 1 of 2 treatment regimens, Graftskin or Unna's boot, and were followed in the model for a 12-month period. The analysis was done from the perspective of a commercial health plan; therefore, only direct medical costs were included. Health care resource use included the primary therapeutic intervention, additional compression dressings, physician office visits, home health visits, laboratory tests and procedures, management of adverse events, and hospitalizations. The model estimated the annual medical cost of managing patients with hard-to-heal venous leg ulcers to be $20,041 for those treated with Graftskin and $27,493 for those treated with Unna's boot. In addition, treatment with Graftskin led to approximately 3 more months in the healed state per person per year than did treatment with Unna's boot. Because patients treated with Graftskin experienced improved healing compared with those treated with compression therapy using Unna's boot, they required fewer months of treatment for unhealed ulcers. As a result, the use of Graftskin for treating hard-to-heal venous leg ulcers resulted in lower overall treatment costs.