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The lasing characteristics of mid-IR type-II “W” [InAs/GaInSb/InAs/AlAsSb] structures are found to correlate strongly with the growth conditions and low-temperature photoluminescence (PL) properties. The highest PL intensities and narrowest PL lines are obtained when the wafers are grown at ≈480–510°C with mixed interface bonds. A number of structures grown at a non-optimal lower temperature (≈425°C) nonetheless yielded lower lasing thresholds, lower internal losses, and longer Shockley-Read lifetimes than any grown previously on the present Riber 32P MBE system. All of the laser spectra display regularly-spaced multiple peaks that are consistent with periodic modulation of the cavity loss due to mode-leakage into the GaSb substrate.

We have studied how the photoluminescence (PL) and lasing characteristics of mid-IR type II “W” [InAs/Ga1−xInxSb/InAs/AlAsySb1−y] structures depend on the molecular beam epitaxy growth conditions. The growth temperature that yields the highest PL intensities and narrowest PL lines is found to be in the ≈480–510 °C range, which is considerably higher than the temperatures used in previous type II antimonide laser growths. Also contrary to earlier reports is our observation that using migration-enhanced epitaxy to force an InSb-like interface bond type is detrimental to the laser performance. The PL intensity at 78 K is found to correlate closely with the PL intensities and linewidths at all temperatures, as well as the lasing linewidths, thresholds, and efficiencies. Even though the tested laser structures were grown at a nonoptimal lower substrate temperature of 425 °C, they nonetheless yielded much better morphology, better-resolved x-ray features, stronger PL intensities, narrower PL linewidths, lower lasing thresholds ( 20 ns at 78 K) than any previous antimonide lasers grown on the present Riber 32P molecular beam epitaxy system.

The cardiac Na+/Ca2+exchanger (NCX) in trout exhibits profoundly lower temperature sensitivity in comparison to the mammalian NCX. In this study, we attempt to characterize the regions of the NCX molecule that are responsible for its temperature sensitivity. Chimeric NCX molecules were constructed using wild-type trout and canine NCX cDNA and expressed in Xenopus oocytes. NCX-mediated currents were measured at 7, 14, and 30°C using the giant excised-patch technique. By using this approach, the differential temperature dependence of NCX was found to reside within the NH2-terminal region of the molecule. Specifically, we found that ∼75% of the Na+/Ca2+exchange differential energy of activation is attributable to sequence differences in the region that include the first four transmembrane segments, and the remainder is attributable to transmembrane segment five and the exchanger inhibitory peptide site.

Numerous studies have failed to detect any long-term consequences of involvement by absent parents on their children's well-being beyond the effects of financial transfers. However, many of these studies often narrowly define involvement as parent-child contact and do not address possible joint effects between parental involvement and other variables. In this study, the author used a sample of 269 cases from two waves of the National Survey of Families and Households to explore the possible effects of (a) levels of child-absent parent activity and (b) interactions between child-absent parent activity and financial transfers from absent parents on children's educational attainment. The author found that although activities by themselves have no significant effect, combining activities with financial support increases the probability both that youths will graduate from high school and that they will go on to college. The author discusses the theoretical and policy-oriented implications of these findings.

The effects of gamma radiation on Fabry–Perot interband cascade lasers (ICLs) were investigated. Two ICLs were exposed to cobalt-60 gamma rays for a total dose of 500 krad(Si) each. The ICLs do not show any evidence of changes in performance, including output power, threshold current, slope efficiency, or spectral frequency. These results demonstrate that ICLs are insensitive to gamma irradiation up to exposure rates above those normally encountered within a shielded spacecraft.

Longwave infrared detectors using p-type absorbers composed of InAs-rich type-II superlattices (T2SLs) nearly always suffer from high surface currents due to carrier inversion on the etched sidewalls. Here, we demonstrate reticulated shallow etch mesa isolation (RSEMI): a structural method of reducing surface currents in longwave single-band and midwave/longwave dual-band detectors with p-type T2SL absorbers. By introducing a lateral shoulder to increase the separation between the n+ cathode and the inverted absorber surface, a substantial barrier to surface electron flow is formed. We demonstrate experimentally that the RSEMI process results in lower surface current, lower net dark current, much weaker dependence of the current on bias, and higher uniformity compared to mesas processed with a single deep etch. For the structure used, a shoulder width of 2 μm is sufficient to block surface currents.

We propose an integrated silicon photonic multispectral infrared platform for combining laser power spanning the ultraviolet to the mid-wave infrared from hybrid silicon III-V lasers by spectral beam combining with a novel ultra-broadband combiner.

We report a narrow-ridge interband cascade laser emitting at λ ≈3.5 μm that produces up to 592 mW of cw power with a wallplug efficiency of 10.1% and beam quality factor of M(2) = 3.7 at T = 25 °C. A pulsed cavity length study of broad-area lasers from the same wafer confirms that the 7-stage structure with thicker separate confinement layers has a reduced internal loss of ≈3 cm(-1). More generally, devices from a large number of wafers with similar 7-stage designs and wavelengths spanning 2.95-4.7 μm exhibit consistently higher pulsed external differential quantum efficiencies than earlier state-of-the-art ICLs.

We report a narrow-ridge interband cascade laser emitting at λ ≈ 3.5 μm that produces up to 592 mW of cw power with a wallplug efficiency of 10.1% and beam quality factor of M2 = 3.7 at T = 25 °C. Furthermore, devices from a large number of wafers with similar 7-stage designs and wavelengths spanning 2.8-4.7 μm exhibit consistently higher pulsed external differential quantum efficiencies than earlier state-of-the-art ICLs.

We report a 7-stage narrow-ridge interband-cascade laser emitting at l a 3.5 mm that produces up to 592 mW of cw power, with a wallplug efficiency of 10.1% and M2 = 3.7 at T = 25 °C.

The Na+/Ca2+ exchanger plays a prominent role in regulating intracellular Ca2+ levels in cardiac myocytes and can serve as both a Ca2+ influx and efflux pathway. A novel inhibitor, KB-R7943, has been reported to selectively inhibit the reverse mode (i.e. , Ca2+ entry) of Na+/Ca2+ exchange transport, although many aspects of its inhibitory properties remain controversial. We evaluated the inhibitory effects of KB-R7943 on Na+/Ca2+exchange currents using the giant excised patch-clamp technique. Membrane patches were obtained from Xenopus laevis oocytes expressing the cloned cardiac Na+/Ca2+exchanger NCX1.1, and outward, inward, and combined inward-outward currents were studied. KB-R7943 preferentially inhibited outward (i.e., reverse) Na+/Ca2+ exchange currents. The inhibitory mechanism consists of direct effects on the transport machinery of the exchanger, with additional influences on ionic regulatory properties. Competitive interactions between KB-R7943 and the transported ions were not observed. The antiarrhythmic effects of KB-R7943 were then evaluated in an ischemia-reperfusion model of cardiac injury in Langendorff-perfused whole rabbit hearts using electrocardiography and measurements of left ventricular pressure. When 3 μM KB-R7943 was applied for 10 min before a 30-min global ischemic period, ventricular arrhythmias (tachycardia and fibrillation) associated with both ischemia and reperfusion were almost completely suppressed. The observed electrophysiological profile of KB-R7943 and its protective effects on ischemia-reperfusion-induced ventricular arrhythmias support the notion of a prominent role of Ca2+ entry via reverse Na+/Ca2+ exchange in this process.

Ion transport and regulation of Na(+)-Ca(2+) exchange were examined for two alternatively spliced isoforms of the canine cardiac Na(+)-Ca(2+) exchanger, NCX1.1, to assess the role(s) of the mutually exclusive A and B exons. The exchangers examined, NCX1.3 and NCX1.4, are commonly referred to as the kidney and brain splice variants and differ only in the expression of the BD or AD exons, respectively. Outward Na(+)-Ca(2+) exchange activity was assessed in giant, excised membrane patches from Xenopus laevis oocytes expressing the cloned exchangers, and the characteristics of Na(+)(i)- (i.e., I(1)) and Ca(2+)(i)- (i.e., I(2)) dependent regulation of exchange currents were examined using a variety of experimental protocols. No remarkable differences were observed in the current-voltage relationships of NCX1.3 and NCX1.4, whereas these isoforms differed appreciably in terms of their I(1) and I(2) regulatory properties. Sodium-dependent inactivation of NCX1.3 was considerably more pronounced than that of NCX1.4 and resulted in nearly complete inhibition of steady state currents. This novel feature could be abolished by proteolysis with alpha-chymotrypsin. It appears that expression of the B exon in NCX1.3 imparts a substantially more stable I(1) inactive state of the exchanger than does the A exon of NCX1.4. With respect to I(2) regulation, significant differences were also found between NCX1.3 and NCX1.4. While both exchangers were stimulated by low concentrations of regulatory Ca(2+)(i), NCX1.3 showed a prominent decrease at higher concentrations (1 microM). This does not appear to be due solely to competition between Ca(2+)(i) and Na(+)(i) at the transport site, as the Ca(2+)(i) affinities of inward currents were nearly identical between the two exchangers. Furthermore, regulatory Ca(2+)(i) had only modest effects on Na(+)(i)-dependent inactivation of NCX1.3, whereas I(1) inactivation of NCX1.4 could be completely eliminated by Ca(2+)(i). Our results establish an important role for the mutually exclusive A and B exons of NCX1 in modulating the characteristics of ionic regulation and provide insight into how alternative splicing tailors the regulatory properties of Na(+)-Ca(2+) exchange to fulfill tissue-specific requirements of Ca(2+) homeostasis.

Duodenal somatostatinoma is a rare cause of upper gastrointestinal bleeding. We report the case of a 55-yr-old woman who presented with upper gastrointestinal hemorrhage due to a duodenal somatostatinoma. We discuss the characteristics of these tumors, and review the literature on diagnostic workup and management.

A single-mode output power of 41 mW has been obtained at T=120 K and lambdaap3.44 mum from a narrow-ridge interband cascade laser patterned with a Ge distributed-feedback grating. The sidemode suppression ratio at the maximum power is 23 dB, and the linewidth of 0.1 nm is instrument-limited. An alternate contacting geometry yielded robust single-mode output over a broad range of currents and temperatures, and current tuning of the wavelength by up to 17 nm

We present a systematic study of the magnetotransport and magnetic properties of the half-doped La0.5Ca0.5MnO3+δ system. The solid is a metamagnet which undergoes a first-order antiferromagnet (AFM) to ferromagnet (FM) phase transition under a field or by changing temperature. Associated with the AFM–FM transition is an insulator to metal transition. A maximum 109-fold magnetoresistance ratio has been observed at 4.2 K between the least and the most conductive states. At low T (⩽50 K), we have also observed two additional metastable electronic states in the canted AFM state at certain fields. The resistivity of each state differs from one another by at least one order of magnitude. The existence of these multiple states may be related to the unique charge- and spin-ordered state of the half-doped manganite.

Although prior research suggests that sexual minorities are at equivalent or greater risk of sexual assault compared with heterosexual women, few studies have examined simultaneously a broad array of assault types, the forms of force and pressure experienced, and the relative risks of experiencing different kinds of assault or force or pressure during an assault according to sex and sexual orientation. Moreover, very little is known about how subjective interpretations of assault may differ by sex and sexual orientation. We address these gaps using a multimethodological analysis of original survey data ( N = 342) with a snowball oversample of sexual minority respondents. Quantitative results indicate that both sexual minority status and sex are predictive of increased assault risk of most assault types, but that most effects of sexual minority status are restricted to men. The probabilities of experiencing verbal pressure or physical force are largely uniform across categories. Qualitative analyses of open-ended questions suggest that men and women interpret the experience of assault differently, such that sexual minority men conceptualize their unwanted sexual experiences as “giving in” due to feelings of guilt or low self-worth, whereas women of all sexual orientations acquiesced because it was perceived to be easier or more practical than resisting. Theoretical implications and directions for future research are discussed.

We discuss approaches to increasing the cw output power of the interband cascade lasers (ICLs) for the midwave infrared spectral region. While most of the attention to date has been focused on reducing the operating power of the ICL, the optimization for maximum output power proceeds in a different direction. We find that increasing the number of stage is beneficial, in that it boosts the slope efficiency with only a modest penalty due to higher threshold power density and extra heating. The critical figure of merit for realizing high-power ICLs is the internal loss, which can be estimated from the external differential quantum efficiency (EDQE) per stage. The internal loss can be controlled by varying the thickness of the low-doped GaSb separate-confinement layers (SCLs). We demonstrate room-temperature EDQEs approaching 45% for broad-area 7-stage ICLs with 800-nm-thick SCLs.

We discuss two distinct approaches to realizing distributed-feedback (DFB) interband cascade lasers (ICLs) for emission in the mid-IR. In the top-grating approach, the first-order gratings are produced by patterning high-index germanium layers on top of narrow ridges with relatively thin top claddings. One 7-μm-wide device emitting at λ = 3.8 μm generated over 27 mW of cw single-mode output at 40°C, with a side-mode-suppression ratio

We report 7-stage thick-separate-confinement interband cascade lasers with emission at λ= 3.1-3.8 m and pulsed external differential quantum efficiency up to 55% at room temperature, which corresponds to internal loss < 3 cm-1.

Electron-beam lithography was used to pattern a second-order photonic-crystal distributed feedback grating onto an antimonide type-II "W" laser emitting at /spl lambda//spl ap/3.7 /spl mu/m. For pulsed optical pumping, the output beam was essentially diffraction-limited up to a stripe width of 150 /spl mu/m, and remained no worse than eight times the diffraction limit for stripes as wide as 600 /spl mu/m. This represents a considerable improvement over all previous mid-infrared semiconductor lasers with such broad stripes.

The ‘hands off doctrine’ defined the relationship between the federal courts and departments of corrections. The doctrine remained securely in place until the 1960s and 1970s when the actions combined with exceptionally poor prison conditions in Alabama and Arkansas combined to breech the doctrine. Once the doctrine was breached, violations of the full range of constitutional rights became causes of action for inmates.

We report interband cascade vertical-cavity surface-emitting lasers (ICVCSELs) that operate in pulsed mode at temperatures up to 70 °C. Their emission at λ ≈ 3.4 μm extends considerably the previous longest wavelength of 3.0 μm for an electrically-pumped vertical-cavity surface-emitting laser operating at room temperature. The output from mesas having diameters ranging from 30 to 60 μm (with emission aperture diameters of 20–50 μm) is circularly symmetric, and the threshold current densities at T = 25 °C are as low as 390 A/cm2. However, the differential slope efficiencies are low, e.g., ≤50 mW/A at T = 25 °C, due to loss in the top and bottom mirrors and reduced current efficiency. The smallest device operates in a single spectral mode despite having an emission aperture much wider than the wavelength.

We demonstrate cw output powers >290 mW into a nearly diffraction-limited (M2 ≈2.2) output beam from an interband cascade laser operating at λ = 3.6-3.7 μm at room temperature. The interband cascade laser was designed for nearly equal electron and hole populations in the active region with heavy electron-injector doping, and was processed into narrow ridges mounted epitaxial side down on a copper heat sink. A 15.7-μm-wide, 4-mm-long ridge with the back facet coated for high reflection (HR) and an anti-reflection-coated front facet produced 253 mW of cw output power at T = 25°C into a beam with M2 ≈2.7. Furthermore, corrugating the sidewalls of the ridge leads to a 20% improvement in the brightness. A 15.7-μm-wide, 0.5-mm-long ridge with an HR-coated back facet and an uncoated front facet exhibited a maximum cw wall-plug efficiency of nearly 15% at room temperature.

A rapid series of recent performance advances have established the interband cascade laser (ICL) as a practical midwave infrared (mid-IR) diode source that may be expected to find broad use in a variety of applications ranging from infrared countermeasures to chemical spectroscopy. The ICL is effectively a hybrid of the conventional diode laser, in that injected electrons and holes recombine to create photons, and the quantum cascade laser (QCL), in that a multi-stage staircase of active quantum wells is connected in series. The ICL also differs from both, however, in that most of the electrons and holes needed for lasing are created internally at semimetallic interfaces separating the stages rather than being injected from the contacts. The ICL performance recently improved dramatically when “carrier rebalancing”, via heavy n-type doping of the electron injector regions, was introduced to equalize the electron and hole populations in the active quantum wells [1]. Recent publications have reported cw operation up to 109 °C, cw output power up to 158 mW at room temperature (RT, taken here to be 25 °C), RT cw wallplug efficiency up to 13.5%, RT cw drive power as low as 29 mW (more than 20 times lower than the best QCLs results reported to date), and RT cw operation to wavelengths as long as 5.7 μm [1,2]. Here we discuss further improvements of the lasing characteristics that occur when the ICLs are mounted epitaxial-side-down (epi-down), using a proprietary NRL procedure that combines high performance with high processing yield.

The performance of mid-IR interband cascade lasers (ICLs) has been improved by introducing heavier doping into the electron injector regions with the purpose of increasing the electron density in the active region to the level commensurate with the active hole density. For devices emitting at wavelengths in the 3.6-3.9 P m range, the improvements include pulsed room temperature (R T) threshold current density as low as 170 A/cm 2 , maximum cw operating temperature as high as 109 oC, and RT cw input power as low as 29 mW. Epi-down-mounted ridges display RT cw wall-plug efficiencies as high as 14.6% as well as emission of > 200 mW into a nearly diffraction-limited beam. RT cw operation has also been demonstrated for considerably longer wavelengths extending to 5.7 P m with threshold power densities of | 1kW/cm 2 , which are an order of magnitude lower than those in state-of-the-art quantum cascade lasers. The very low operating powers ar e expected to lengthen battery lifetimes and greatly relax packaging and size/weight requirements for fielded chemical-sensing systems. Keywords: Input power, interband cascade laser, mid-infrared, threshold current density, chemical sensing. 1. INTRODUCTION The interband cascade laser (ICL) is a GaSb-base multi-stage diode emitter that employs type-II interband active transitions.

The recent availability of midwave-IR semiconductor lasers capable of emitting narrow spectral lines at ambient or thermoelectric-cooler temperatures (above -20 deg C) has spawned the development of a new generation of chemical sensing systems designed to exploit the prevalence of strong mid-IR spectroscopic signatures. Although the required laser output powers tend to be rather modest (less than or equal 1mW), minimizing the drive power can be critical because the most attractive systems will be quite compact and often powered by batteries. Several distinct classes of mid-IR semiconductor lasers are currently being developed. The antimonide interband cascade laser (ICL) combines the interband active transitions of a conventional diode laser with the multiple cascaded stages of a quantum cascade laser (QCL). Previous ICLs demonstrated spectral coverage of at least 2.9 4.2 microns, and continuous wave operation up to 72 deg. C. Redesigned ICLs incorporating carrier rebalancing have, by several key figures of merit, displayed record-setting performance compared to all previous mid-IR semiconductor lasers.

We have substantially improved the performance of interband cascade lasers emitting at λ = 4.7 and 5.6 μm, by applying the recently-pioneered approach of heavily doping the injector regions to rebalance the electron and hole concentrations in the active quantum wells. Ridges of ≈10 μm width, 4 mm length, and high-reflectivity back facets achieve maximum continuous wave operating temperatures of 60°C and 48°C, respectively. The threshold power density of ≈1 kW/cm2 at T = 25°C is over an order of magnitude lower than for state-of-the-art quantum cascade lasers emitting in this spectral range.

An interband cascade laser design has been grown by molecular beam epitaxy using uncracked arsenic and antimony sources. Lasers were fabricated into both broad-area and narrow-ridge devices, with cavity lengths ranging between 1 mm and 4 mm. At 300K, under low-duty-cycle pulsed conditions, threshold current densities for lasers with 2-mm cavity lengths are as low as 395 A/cm2, with optical emission centered at a wavelength of ~3.82 μm at 300 K. Continuous-wave (cw) performance of the narrow-ridge devices has been achieved for temperatures up to almost 60°C. We present results of both pulsed (broad-area and ridge) and cw (ridge only) measurements on these lasers, including L-I-V, spectral, cavity-length, and Hakki-Paoli analyses.

Our simulations find that the active quantum wells in previous mid-IR interband cascade laser (ICL) designs have invariably contained far more holes than electrons. Further modeling shows that the carrier populations can be rebalanced by heavily doping the electron injector regions to levels more than an order of magnitude higher than in any earlier devices. The experimental implementation of this strategy has dramatically improved nearly all ICL performance characteristics. For devices emitting at wavelengths in the 3.6-3.9 μm range, this includes pulsed room temperature (RT) threshold current density as low as 170 A/cm 2 , maximum cw operating temperature as high as 109 °C, RT cw output power as high as 159 mW, RT cw wallplug efficiency as high as 13.5%, and RT cw input power as low as 29 mW. We also demonstrate RT cw operation to wavelengths as long as 5.7 μm. The extremely low input power to reach threshold, which is more than 25 times lower than the best ever reported for a quantum cascade laser, will strongly impact battery lifetimes and other system requirements in fielded chemical sensing applications.

Neuronal optical excitation can provide non-contacting tools to explore brain circuitry and a durable stimulation interface for cardiac pacing and visual as well as auditory sensory neuronal stimulation. To obtain accurate absorption spectra, we scan the transmission of neurons in cell culture medium, and normalize it by subtracting out the absorption spectrum of the medium alone. The resulting spectra show that the main neuronal absorption peaks are in the 3000- 6000nm band, although there is a smaller peak near 1450nm. By coupling the output of a 3μm interband cascade laser (ICL) into a mid-IR fluorozirconate fiber, we can effectively deliver more than 1J/cm2 photon intensity to the excitation site for neuronal stimulation.

The interband cascade laser (ICL) is a unique device concept that combines the effective parallel connection of its multiple-quantum-well active regions, interband active transitions, and internal generation of electrons and holes at a semimetallic interface within each stage of the device. The internal generation of carriers becomes effective under bias, and the role of electrical injection is to replenish the carriers consumed by recombination processes. Major strides have been made toward fundamentally understanding the rich and intricate ICL physics, which has in turn led to dramatic improvements in the device performance. In this article, we review the physical principles of the ICL operation and designs of the active region, electron and hole injectors, and optical waveguide. The results for state-of- the-art ICLs spanning the 3-6 μm wavelength range are also briefly reviewed. The cw threshold input powers at room temperature are more than an order of magnitude lower than those for quantum cascade lasers throughout the mid-IR spectral range. This will lengthen battery lifetimes and greatly relax packaging and size/weight requirements for fielded sensing systems.

The cw operating temperature of ICLs emitting at 3.9, 4.7 and 5.6 μm is extended to 107 °C, 60°C, and 48°C, respectively. The threshold powers range from several tens to several hundred mW at 25°C.

We demonstrate butt-coupling of a 3.4 μm interband cascade laser into a 3.7 μm thick by 7 μm wide GeSbS chalcogenide ridge waveguide and measure a total insertion loss of −28 dB.

We report cw interband cascade lasers operating to 109 °C, which at room temperature emit at wavelengths > 5.5 μm with output powers > 150 mW, wallplug efficiencies > 13%, and input powers < 30 mW.

Context.—The monoclonal antibody A103 recognizes an antigen on melanoma cells known as Melan-A or MART-1. Recent studies have shown that A103 also reacts with adrenal cortical cells and may be useful in the diagnosis of adrenal cortical tumors. However, only small numbers of some of the tumors in the differential diagnosis of adrenal cortical neoplasms have been studied. Objective.—To study the specificity of A103 immunohistochemistry in a large number of tumors in the differential diagnosis of adrenal cortical neoplasms. Design.—Formalin-fixed, paraffin-embedded tissue from 21 adrenal cortical tumors, 16 cases of metastatic carcinoma to the adrenal, 10 pheochromocytomas, and 269 extra-adrenal carcinomas was evaluated for A103 immunoreactivity using a commercially available antibody (Novocastra, Newcastle, UK). Results.—Positive staining was seen in all of the adrenal cortical tumors but in none of the adrenal metastases or pheochromocytomas. In the 269 extra-adrenal carcinomas, A103 immunoreactivity was limited to a single ovarian serous carcinoma. Conclusion.—A103 immunostaining is useful in distinguishing adrenal cortical neoplasms from other carcinomas and pheochromocytoma.

The interband cascade laser differs from any other class of semiconductor laser, conventional or cascaded, in that most of the carriers producing population inversion are generated internally, at semimetallic interfaces within each stage of the active region. Here we present simulations demonstrating that all previous interband cascade laser performance has suffered from a significant imbalance of electron and hole densities in the active wells. We further confirm experimentally that correcting this imbalance with relatively heavy n-type doping in the electron injectors substantially reduces the threshold current and power densities relative to all earlier devices. At room temperature, the redesigned devices require nearly two orders of magnitude less input power to operate in continuous-wave mode than the quantum cascade laser. The interband cascade laser is consequently the most attractive option for gas sensing and other spectroscopic applications requiring low output power and minimum heat dissipation at wavelengths extending from 3 μm to beyond 6 μm.

We report that various recent design modifications and optimizations have produced significant advances in the performance of interband cascade lasers (ICLs) for the mid-IR spectral band. Figure 1 illustrates the progression with time of ICL pulsed threshold current densities, as compared to some of the lowest reported results for quantum cascade lasers. All of the ICL devices were standard 150-µm-wide broad-area ridges with 2 mm cavity lengths. Note that thresholds for all of the latest generation of ICL designs (labeled Gen3) decreased substantially, to the 170–260 A/cm2 range. Figure 2 shows threshold power densities (P th = current density × voltage) as a function of wavelength for the last four generations of 5-stage devices. Note that the Gen3 power densities are substantially lower than any of the earlier results, and that they fall below the dashed curve corresponding to probable room-temperature cw operation at wavelengths as long as 5.5 µm.

Semiconductor laser sources for the critical 3–5 um spectral range are evolving and improving rapidly, with significant advancements reported within the last year for three fundamentally different approaches: the intersubband quantum cascade laser (QCL),1 the type-I quantum well (QW) diode laser,2 and the interband cascade laser (ICL).3 Of these three, the most promising candidate to cover the entire wavelength range is the antimonide-based type-II ICL as designed and grown at the Naval Research Laboratory (NRL). Broad area devices have already demonstrated threshold power densities (P th = current density × voltage) which will enable room temperature (RT) continuous-wave (CW) operation from 2.9 out to 4.6 μm (Fig. 1). The ICL architecture appears uniquely poised not only to offer complete spectral coverage (3–5 μm) but also to operate with low power dissipation. Some of the most recent ICLs display P th th reported to date for QCLs operating at the same temperature. For this reason, the ICL approach is favored for applications demanding low power and excess heat dissipation, e.g., for long battery lifetimes in the field.

Interprofessional collaboration in health care is believed to enhance patient outcomes. However, where professions have overlapping scopes of practice (eg, chiropractors and physical therapists), "turf wars" can hinder effective collaboration. Deep-rooted beliefs, identified as implicit attitudes, provide a potential explanation. Even with positive explicit attitudes toward a social group, negative stereotypes may be influential. Previous studies on interprofessional attitudes have mostly used qualitative research methodologies. This study used quantitative methods to evaluate explicit and implicit attitudes of physical therapy students toward chiropractic.A paper-and-pencil instrument was developed and administered to 49 individuals (students and faculty) associated with a Canadian University master's entry-level physical therapy program after approval by the Research Ethics Board. The instrument evaluated explicit and implicit attitudes toward the chiropractic profession. Implicit attitudes were determined by comparing response times of chiropractic paired with positive versus negative descriptors.Mean time to complete a word association task was significantly longer (t = 4.75, p =.00) when chiropractic was associated with positive rather than negative words. Explicit and implicit attitudes were not correlated (r = 0.13, p =.38).While little explicit bias existed, individuals associated with a master's entry-level physical therapy program appeared to have a significant negative implicit bias toward chiropractic.

Lateral structure is investigated in two antimonide superlattices using x-ray diffraction. We report periodic lateral modulation in AlSb/AlAs digital superlattices, while no lateral modulation is observed in similar InAs/Al(In)Sb digital superlattices. By fitting the diffraction data with dynamical diffraction theory we are able to determine the strain in each layer and at the interfaces. The findings are consistent with recent predictions of the critical thickness for three-dimensional growth.

In order to be commercially viable, the type-II superlattice (T2SL) LWIR focal plane array technology will require the development of effective passivation of exposed surfaces. Here we investigate the relationship between the thickness and composition of the native oxide at the T2SL-SiO2 interface and the diode performance in terms of sidewall resistivity. Device performance is compared between samples with untreated surfaces, those for which the native oxides have been removed at various intervals prior to SiO2 deposition, and samples for which oxide growth was promoted by ozone exposure with and without a prior oxide strip. InAs- and GaSb-capped pieces were processed in an identical manner and studied using X-ray photoelectron spectroscopy (XPS). From these spectra, the compositions and thicknesses of the surface oxides just prior to SiO2 deposition were determined, complementing the electrical characterization of devices. Correlation of the performance and surface composition is presented.