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We report the intrinsic linewidth in a photonic crystal surface-emitting laser diode. An intrinsic linewidth of 330 kHz was obtained without any optical feedback, one order smaller than the value of DFB lasers. The impact of cavity feedback on linewidth was also characterized.

Metal-assisted chemical etching (MacEtch) is an emerging anisotropic chemical etching technique that has been used to fabricate high aspect ratio semiconductor micro- and nanostructures. Despite its advantages in unparalleled anisotropy, simplicity, versatility, and damage-free nature, the adaptation of MacEtch for silicon (Si)-based electronic device fabrication process is hindered by the use of a gold (Au)-based metal catalyst, as Au is a detrimental deep-level impurity in Si. In this report, for the first time, we demonstrate CMOS-compatible titanium nitride (TiN)-based MacEtch of Si by establishing a true vapor-phase (VP) MacEtch approach in order to overcome TiN-MacEtch-specific challenges. Whereas inverse-MacEtch is observed using conventional liquid phase MacEtch because of the limited mass transport from the strong adhesion between TiN and Si, the true VP etch leads to forward MacEtch and produces Si nanowire arrays by engraving the TiN mesh pattern in Si. The etch rate as a function of etch temperature, solution concentration, TiN dimension, and thickness is systematically characterized to uncover the underlying nature of MacEtching using this new catalyst. VP MacEtch represents a significant step toward scalability of this disruptive technology because of the high controllability of gas phase reaction dynamics. TiN-MacEtch may also have direct implications in embedded TiN-based plasmonic semiconductor structures for photonic applications.

Static and dynamic characteristics of quantum well lasers are simulated and their dependence on volume of active region and quality factor of cavity are obtained using a three-rate equation model. Energy cost of 0.06 fJ/bit is obtained from a proposed nanobeam cavity Photonic crystal laser.

Low exergy building systems generate new possibilities for the design of high performance buildings, especially when the design of a new building is considered as part of a district where the relationship between buildings are optimized to minimize the dispersion of energy in the environment and maximize the recovery of waste energy. We present an innovative design concept and the performance assessment of the heating system of the new Embodied Computation Laboratory at Princeton University. The system is demonstrated to be able to match the heat demand without need for backup systems.

We have developed novel sensing techniques to understand mean radiant temperature and indoor air quality for a holistic understanding of indoor environment quality. A novel scanning mean radiant temperature sensor provides a spatially resolved description of the radiant heat transfer from all surfaces in a space. A low-cost deployable indoor air quality (iAQ) sensor system is capable of measuring CO2, VOC, CO, NOx, Formaldehyde, temperature and humidity. We claim the associated results of these two projects can radically improve building control algorithms, as well as inform the planning process of new buildings. We present the findings from developing and deploying the novel scanning sensor and the indoor air quality system. We demonstrate that these tools make it possible to discover sources of pollution, optimize air quality, increase system performance, and improve energy efficiency. The sensors are described and preliminary data presented.

Objectives: Develop a built environment mapping workflow. Implement the workflow in the emergency department (ED). Demonstrate the actionable representations of the data that can be collected using this workflow. Background: The design of the healthcare built environment impacts the delivery of patient care and operational efficiency. Studying this environment presents a series of challenges due to the limitations associated with existing technology such as radio-frequency identification. The authors designed a customized mapping workflow to collect high-resolution spatial, temporal, and activity data to improve healthcare environments, with emphasis on patient safety and operational efficiency. Method: A large, urban, academic medical center ED collaborated with an architecture firm to create a data collection, and mapping workflow using ArcGIS tools and data collectors. The authors developed tools to collect data on the entire ED, as well as individual patients, physicians, and nurses. Advanced visual representations were created from the master data set. Results: In 48 consecutive hourly snapshots, 5,113 data points were collected on patients, physicians, nurses, and other staff reflecting the operations of the ED. Separately, 84 patients, 10 attending physicians, 10 resident physicians, and 17 nurses were tracked. Conclusions: The data obtained from this pilot study were used to create advanced visual representations of the ED environment. This cost-effective ED mapping workflow may be applied to other healthcare settings. Further investigation to evaluate the benefits of this high-resolution data is required.

Three-dimensionally confined semiconductor quantum dots have emerged to be a versatile material system with unique physical properties for a wide range of device applications. With the advances in nanotechnology and material growth techniques for both epitaxial and colloidal quantum dots, recently the research has been shifted largely towards quantum dot based devices for practical applications. In this short review, we have tried to assemble a selection of recent advances in the areas of quantum dots for computing and communications, solid state lighting, photovoltaics, and biomedical applications that highlight the state of the art.

To better understand the extent of how the air temperature and mean radiant temperature may vary both spatially and temporally in a radiantly heated space, we conducted a seven-day experiment in the architectural laboratory at School of Architecture, Princeton University. The primary intent of this paper was to decouple the measurement of the air temperature and mean radiant temperature. We collected a large dataset that shows temporal and spatial variations. To do so, we used non-contact infrared thermometer to measure the surface temperatures of the surrounding surfaces inside the laboratory. The geometry of the laboratory is simplified into a box, the corresponding view factor from every point within the box can be calculated towards each internal surface. These view factors are then combined with the measured surface temperatures to produce mean radiant temperatures. This spatial mean radiant temperature distribution was then compared with the air temperature distribution measured by the air temperature sensors suspended from the ceiling of the laboratory. We believe making these data available will help future researchers working on similar problems to develop protocols than the state-of-the-art measurement techniques observed among different thermal comfort or radiant heat transfer research.

We report here on one-dimensional (1D) grating couplers based on hybrid silicon/LNOI platform for polarization-independent and high-efficient single-polarization coupling efficiencies. A low index oxide buffer layer was introduced in between the top silicon high index grating coupler and bottom LNOI waveguide. With optimal design of the buffer layer thicknesses, modal and index matches can be tuned for either single polarization or both TE/TM polarization coupling applications. Over 70% coupling efficiency can be achieved for single polarization based on the basic uniform 1D grating coupler design without any bottom reflectors incorporated. Polarization independent coupling efficiency of 51% was also achieved. The spectral bandwidth is over 50 nm with polarization dependent loss of 0.1 dB. The proposed structure is simple to fabricate. Detailed modal and loss analysis suggest different dominant loss mechanisms in the proposed hybrid structure, where the introduction of the bottom mirror may not result in significant improvement in coupling efficiency, as the dominant loss mechanism arises from the top reflection loss.

Determining variations in air temperature and mean radiant temperature (MRT), two primary environmental parameters directly linked to thermal comfort, can be challenging. The ease and effectiveness of both measurement and simulation are quite different for determining air temperature and MRT. We review these challenges and present an experiment demonstrating how these differences in complexity and resolution can lead to challenges coupling these variables, whose effect on thermal comfort is interdependent. Bearing these challenges in mind, we measured and simulated the air temperatures and MRTs inside a radiantly heated high bay laboratory space. We found the spatial variation of the MRTs to vary by 5 °C at the elevation of 1.3 m, which is much larger than the variations observed in air temperature. The variations in measured air temperature were up to 2 °C. This calls for improvement to current tools and methodologies for measuring and simulating the radiant environment, particularly at locations closer to the exterior envelope where hot and cold surfaces affect both air temperature and MRT. It is important to improve the evaluation techniques for MRT, as we observe its spatial variation to be much greater than that of air temperature, while its measurement is limited and usually ignored in practice.

Defying text definitions of wet etching, metal-assisted chemical etching (MacEtch), a solution-based, damage-free semiconductor etching method, is directional, where the metal catalyst film sinks with the semiconductor etching front, producing 3D semiconductor structures that are complementary to the metal catalyst film pattern. The same recipe that works perfectly to produce ordered array of nanostructures for single-crystalline Si (c-Si) fails completely when applied to polycrystalline Si (poly-Si) with the same doping type and level. Another long-standing challenge for MacEtch is the difficulty of uniformly etching across feature sizes larger than a few micrometers because of the nature of lateral etching. The issue of interface control between the catalyst and the semiconductor in both lateral and vertical directions over time and over distance needs to be systematically addressed. Here, we present a self-anchored catalyst (SAC) MacEtch method, where a nanoporous catalyst film is used to produce nanowires through the pinholes, which in turn physically anchor the catalyst film from detouring as it descends. The systematic vertical etch rate study as a function of porous catalyst diameter from 200 to 900 nm shows that the SAC-MacEtch not only confines the etching direction but also enhances the etch rate due to the increased liquid access path, significantly delaying the onset of the mass-transport-limited critical diameter compared to nonporous catalyst c-Si counterpart. With this enhanced mass transport approach, vias on multistacks of poly-Si/SiO

We report on the optical gain and loss of waveguides containing lithographically defined quantum dots. Lasing action has previously been demonstrated in a nominally identical structure. Measurements are made by monitoring the transmission of a resonant pulse while varying the injection current. We measure a maximum modal gain of 1.8 cm \(^{{-1}}\) at the peak of the ground state emission for a two-layer structure. The peak gain is insufficient for ground state lasing to be achieved in a structure with as-cleaved facets, but the gain per dot is comparable with that demonstrated in self-assembled quantum dots.

We present the design, fabrication, and characterization of decimated lattice photonic crystal membrane lasers. Based on our simulated designs, decimated photonic crystal lattices have reduced number of holes, which enhance the current and heat conductive paths from the optical cavity with a minimal impact on the cavity quality factor and resonance. Our calculations indicate lower operating temperature using the decimation lattice designs. Two decimated cavity designs are demonstrated and compared to conventional photonic crystal defect cavity lasers in InP-based membranes. The decimated designs show improved laser performance with a small reduction of measured cavity quality factor. Reduction of the photonic crystal holes around the defect cavity to as few as two periods still enables photopumped operation of photonic crystal defect lasers. The improvement in the thermal properties is characterized by varying the photopumping duty cycle.

We present experimental results from an edge-emitting diode laser with an active layer consisting of a 2-D patterned quantum well superlattice. We demonstrate control over the density of optical transitions by engineering the unit cell geometry of the lattice.

Gain-guided lasers with distributed Bragg reflector gratings that exhibit narrow emission linewidths of under 500 kHz are demonstrated. Partial coverage of a facet with a grating is found to be sufficient to ensure single-wavelength laser operation. Narrow linewidth operation in 40 and 150-μm wide lasers with partial gratings is demonstrated. The use of antireflection coatings to suppress spurious Fabry-Perot modes is also presented. Linewidths as low as 200 kHz that are insensitive to drive current are observed.

Semiconductor quantum dot lasers have been extensively studied for applications in future lightwave telecommunications systems. This paper summarizes a tutorial that was presented at the Optical Fiber Communication (OFC) 2010. The motivation for quantum dots in lasers is outlined, and the desirable effects of three dimensional quantum confinement are described. Methods for forming self-assembled quantum dots and the resultant laser characteristics are presented. The formation of patterned quantum dot lasers and the results of this type of quantum dot laser are outlined. Finally, a novel inverted quantum dot structure or nanopore laser containing 3-D quantization formed from an engineered periodicity is introduced.

Although compound semiconductors like gallium arsenide have a substantial performance advantage over silicon in photovoltaic and optoelectronic applications, these do not outweigh the costly process of growing large, high-quality layers of these materials and transferring them to flexible or transparent substrates for use in devices such as solar cells, night vision cameras and wireless communication systems. But now John Rogers and his team demonstrate a new fabrication approach that may remove this disadvantage. They grow films of GaAs and AlGaAs in thick, multilayered assemblies in a single deposition sequence, then release the individual layers and distribute them over foreign substrates by printing. The technological potential of this strategy to large-area applications is illustrated with the fabrication of GaAs devices such as field-effect transistors on glass and photovoltaic modules on sheets of plastic. Although compound semiconductors like gallium arsenide (GaAs) offer advantages over silicon for photovoltaic and optoelectronic applications, these do not outweigh the costly process of growing large layers of these materials and transferring them to appropriate substrates. However, a new fabrication approach is now demonstrated: films of GaAs and AlGaAs are grown in thick, multilayered assemblies in a single sequence; the individual layers are then released and distributed over foreign substrates by printing. Compound semiconductors like gallium arsenide (GaAs) provide advantages over silicon for many applications, owing to their direct bandgaps and high electron mobilities. Examples range from efficient photovoltaic devices1,2 to radio-frequency electronics3,4 and most forms of optoelectronics5,6. However, growing large, high quality wafers of these materials, and intimately integrating them on silicon or amorphous substrates (such as glass or plastic) is expensive, which restricts their use. Here we describe materials and fabrication concepts that address many of these challenges, through the use of films of GaAs or AlGaAs grown in thick, multilayer epitaxial assemblies, then separated from each other and distributed on foreign substrates by printing. This method yields large quantities of high quality semiconductor material capable of device integration in large area formats, in a manner that also allows the wafer to be reused for additional growths. We demonstrate some capabilities of this approach with three different applications: GaAs-based metal semiconductor field effect transistors and logic gates on plates of glass, near-infrared imaging devices on wafers of silicon, and photovoltaic modules on sheets of plastic. These results illustrate the implementation of compound semiconductors such as GaAs in applications whose cost structures, formats, area coverages or modes of use are incompatible with conventional growth or integration strategies.

We report the first study of spontaneous emission from an ordered nanopore array diode laser at 77K. The presence of gaps in the spontaneous emission spectrum supports the theoretically predicted formation of a subband structure in the valence and conduction bands.

A compelling use for high-power, narrow-linewidth fiber lasers and amplifiers is atmospheric Doppler lidars. Such systems require high power, good beam quality, a broad tuning range, and ruggedness. In this paper, we present a ground-based diode-seeded, high-power, narrow-linewidth Yb fiber-amplifier-based Doppler temperature lidar operating at 1083 nm for measuring temperature and density of the neutral atmosphere from 300 to 1000 km. Principles of Doppler resonance fluorescence lidar will be introduced. The current state of the fiber-based lidar system will be addressed, as well as ongoing work to increase SNR through power scaling and improvement of spatial resolution and wind measurement capability via pulsed operation.

In this work, we present an analytical model describing the density of states and spectral behavior of the ordered nanopore array diode laser. The nanopore structure consists of an ordinary quantum well perturbed by a periodic lattice of energy barriers. It is shown that such a perturbation leads to the formation of energy subbands in both the conduction and valence bands. The theoretically predicted gain spectrum shows excellent agreement with experimental results. Finally, the unique effects of in-plane quantization and periodicity on the intersubband selection rules are described in detail.

Three-dimensional (3D) compound semiconductor architectures can be formed when strained semiconductor layers are released from the substrate by selective etching. These 3D nanostructures have potential applications in nanoelectronics, nanophotonics and nanomechanics. In this paper, we report on the formation of In0.2Ga0.8As/GaAs 3D structures using lithographically defined micron-size, open-ended rectangular stripe patterns on films grown by metalorganic chemical vapor deposition (MOCVD). The formation process of nanotubes with diameters smaller than theoretical values has been analyzed. Unambiguous strain direction and crystallographic orientation dependence have been demonstrated. A geometry effect with respect to the longer and shorter sides of the rectangular pattern has been observed, indicating a pathway for high-degree control over the number of turns for such tubes and their positioning by lithographically defined stripe arrays.

Self-assembled quantum dots have been heavily researched in recent years because of the potential applications to quantum electronic and optoelectronic devices they present. The non-uniformity and random ordering resulting from the self-assembly processes, however, are detrimental to potential applications, prohibiting the type of engineering control necessary for complex systems. The work presented in this document has sought to overcome the limitations of self-assembly by combining selective area epitaxy via MOCVD with high-resolution electron beam lithography to achieve lateral control over semiconductor structures at the nanometer scale. Two different structures are presented. The first is patterned quantum dots which improve on the uniformity and order of similar self-assembled quantum dots. The second is an entirely novel structure, the nanopore active layer, which demonstrates the potential for this process to extend beyond the constraints of self-assembly. Experimental and theoretical results for both structures are presented.

Selective area growth (SAG) is a fabrication technique that allows compound semiconductor crystals to grow within laterally defined regions with feature sizes down to submicron to even nanometer scale. In masked SAG, dielectric masks formed by lithography are used to inhibit crystal growth outside the window areas. In this chapter, we provide a brief historical account of the development of SAG technology, a detailed description of the SAG mechanism, and some important applications to illustrate the power of SAG. We cover many essential factors that contribute to the growth dynamics of SAG, including the growth modes, the governing parameters in metal–organic chemical vapor deposition systems that determine the growth process, and diffusion processes that are directly responsible for growth rate enhancement and selectivity. A theoretical model based on vapor-phase diffusion is presented to elucidate the detailed growth kinetics and to predict the final growth profile accurately. Results from this model agree excellently with experimental data. To illustrate the power of SAG, we show three examples on how to use this technique to create a photonic integrated circuit, a novel material system, and a hybrid integrated device with active III–V materials growing on a silicon platform.

We measured the photocurrent density of quantum well (QW) and inverse quantum dot (IQD) photovoltaic devices. The photocurrent per unit area of IQD was enhanced as the carrier confinement became stronger with increasing diameter.

Broadly tunable distributed Bragg reflector (DBR) lasers utilizing metal-filled surface-etched diffraction gratings were fabricated on a GaAs-unstrained quantum well with AlGaAs core and cladding layers. Devices with 200- and 400-mum gratings sections were fabricated. Single-mode devices are fabricated over a broad spectral range, exhibiting over 55 mW of single-facet output power. The optical properties of this structure are analyzed in terms of effective index step between the peak and valley of the grating and scattering loss in the DBR. Discrete devices were fabricated with lasing wavelengths between 846.6 and 862.9 nm at intervals of 1.44nm, representing a range of 16.3 nm. Wavelength tuning by current injection into the DBR section is explored, and a broad tuning range of over 18 nm is measured while single-mode performance is maintained. The spectral linewidth of these devices is measured. The temperature dependence of light versus current, threshold current values, and spectral characteristics are also examined

Semiconductor quantum dots have been widely researched as a means of improving the performance of optoelectronic devices. Self-assembly has been the dominant method of fabricating quantum dots because of its relative ease compared to more explicit techniques. We have developed a method for fabricating quantum dots in a more explicit manner using electron beam lithography and selective-area metal-organic chemical vapor deposition crystal growth. By eliminating the dependence on strain-driven self-assembly, we can avoid the size distribution and resulting inhomogeneously broadened emission spectrum associated with self-assembled quantum dot ensembles. We report on the threshold and spectral properties of patterned quantum dot lasers. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

Control over the location, distribution, and size of quantum dots is essential for the engineering of next-generation semiconductor devices employing these remarkable nanostructures. We describe two approaches for achieving some level of this control in the InGaAs/GaAs material system. The first allows a degree of spatial selectivity by using strain differences in patterned InGaAs thin films as preferential sites for quantum dot growth. This method results in patterns of dots similar to those grown by self-assembly on an unpatterned InGaAs layer. The second method employs more conventional selective area epitaxy using a thin silicon dioxide mask patterned by electron beam lithography. This method allows control over the location of each quantum dot and variation of dot size through manipulation of the mask pattern. We present data on arrays of highly uniform InGaAs quantum dots fabricated in this manner.

We report results of both strain-driven surface segregation of indium from InGaAs thin films as well as selective area epitaxy of InAs quantum dots using these films. InAs segregation from an underlying InGaAs film allows for preferential growth of quantum dots when additional InAs is deposited. By using standard lithography techniques, a two-step selective growth process for quantum dots is achieved. Furthermore, by utilizing self-assembled nanostructures as a template, selective growth of coalesced wires and dots with 100-nm feature sizes are realized.

Metal-assisted chemical etching (MacEtch) has shown tremendous success as an anisotropic wet etching method to produce ultrahigh aspect ratio semiconductor nanowire arrays, where a metal mesh pattern serves as the catalyst. However, producing vertical via arrays using MacEtch, which requires a pattern of discrete metal disks as the catalyst, has often been challenging because of the detouring of individual catalyst disks off the vertical path while descending, especially at submicron scales. Here, the realization of ordered, vertical, and high aspect ratio silicon via arrays by MacEtch is reported, with diameters scaled from 900 all the way down to sub-100 nm. Systematic variation of the diameter and pitch of the metal catalyst pattern and the etching solution composition allows the extraction of a physical model that, for the first time, clearly reveals the roles of the two fundamental kinetic mechanisms in MacEtch, carrier generation and mass transport. Ordered submicron diameter silicon via arrays with record aspect ratio are produced, which can directly impact the through-silicon-via technology, high density storage, photonic crystal membrane, and other related applications.

The Scottish national past was the story of the struggle for civil and religious liberty, reaching its glorious outcome at the Revolution of 1688. With their prologue in the proto-Presbyterian Culdees, collective memories of Scottish nationality ran from Wallace and Bruce, through Knox, to the Covenanters. At each stage in this memory, the heroes of Scotland’s past had overcome the threat posed by their antithesis, whether Edward I or Edward II, the Roman Catholic church, or the later Stuart kings. Both explicitly and implicitly, the narrative of civil and religious liberty framed the commemoration of the Scottish past in the nineteenth century, generating a collective sense of what it meant to be Scottish, explaining or justifying present attitudes and national mores. In a sense, the Glorious Revolution marked the end of Presbyterian history, the closure of a centuries-long struggle to achieve full and coherent Scottish nationality with a free nation and a secure Presbyterian church. It was for this reason that union was made possible. The Scots had proved their point, won their battle, and could give up their statehood, confident that Scottish nationality could never be undone.

This chapter considers the commemoration of the later stage of the Covenanting era, between the Restoration of the Stuart monarchy in 1660 through to the Glorious Revolution in 1688/9. In particular, we will focus on the Covenanter martyrs of the so-called ‘Killing Times’ of the 1680s. Following the imposition of episcopacy at the Restoration, over a quarter of Scottish Presbyterian ministers refused to conform, choosing instead to preach at illegal ‘conventicles’, concentrated mainly in the south-west of Scotland. In response, Charles II set out to suppress this rebellious activity and, as the level of persecution increased, it was a short step to armed revolt. The Covenanters’ victory at Drumclog and their subsequent defeat at Bothwell Bridge in 1679 ushered in a sustained period of intense persecution, including transportation or summary executions for the most unfortunate. Undaunted, these hard-line Presbyterians continued to gather illegally, becoming increasingly militant and militarised. The publication of the Cameronian Sanquhar Declaration in 1680, disavowing allegiance to the King, ushered in harsher responses from the state – anyone unwilling to swear the Abjuration Oath could be executed on the spot.

The purpose of this book is to consider what these monuments meant to those who raised them, and what they signified to the wider Scottish nation at that time. The Presbyterian statues in the Valley Cemetery, the Robert Bruce statue on the Esplanade, and the National Wallace Monument all embody the nineteenth-century passion for monumental commemoration. The reasons for nineteenth-century Scots raising so many monuments to national heroes such as William Wallace and Robert Bruce may at first seem self-evident: these were great men of the past in an age that worshipped the cult of the Great Man. In the words of Thomas Carlyle, ‘Universal History, the history of what man has accomplished in this world, is at bottom the History of the Great Men who have worked here.’ In this view of the past, all the great paradigm shifts of history were traced back to the actions of these leaders of men – to celebrate their lives and achievements was to bathe in the light of their greatness.

The providential-unionist interpretation of the legacy of William Wallace and Robert Bruce might seem unusual in the early twenty-first century, yet few would argue that these patriot heroes are unworthy of a prominent place in the nation’s collective memory. Seen from the perspective of modern Scottish nationalism, the unionist element of the Victorian Wallace is self-evidently ‘wrong’, yet even the most ardent nationalist would agree that nineteenth-century Scots were quite correct to call upon Wallace as one of the founders of Scottish nationality. Wallace, Bruce, Stirling Bridge and Bannockburn still matter; their significance has endured.

If the legacy of Mary Queen of Scots was incapable of finding a home within the definition of Scottish nationality, there were some readings of the past that could accommodate her. As noted in the previous chapter, many Scottish Catholics viewed Mary as a Catholic martyr, someone who stood up for the religion of Rome and its Scottish antecedents in the midst of reforming turmoil. Though growing, the Catholic experience was still on the fringes of Scottish nationality, still finding its place in expressing its identity, yet this was not the only national frame within which the Queen could be placed. We encounter a somewhat unusual deployment of Mary in the exploits of the proto-nationalist and ardent neo-Jacobite Theodore Napier when visiting Fotheringay Castle – another focal point for Marian memory – in February 1908.

Measured in terms of the symbols of nationality common across the rest of nineteenth-century Europe, there can be no doubt that the Scots held an assertive sense of themselves as a distinct nation. Rather than giving up their nationality in favour of British-national institutions, the Scots surrounded themselves with all the signs and symbols of a culturally and historically coherent nation. The Scots had a national museum and national gallery, national monuments, a national poet, national dress and national architecture, as well as a pantheon of national heroes, past and present. Indeed, Scotland in the nineteenth century suffered not so much from a lack of focal points for its nationality than from a surfeit. In the Victorian era there existed a collective pride bordering on collective egotism, an imperial arrogance bound up with landscape, industry, education and Presbyterianism.

At the heart of this book’s examination of the past in nineteenth-century Scotland is the concept of nationality. In its early twenty-first-century definition, nationality tends to signify ‘the status of being a citizen or subject of a particular state’. Nationality is a box ticked on a form, an entry on a birth certificate. One hundred and fifty years ago, however, the significance of nationality ran much deeper. Across nineteenth-century Europe, nationality signified both the collective character of the nation and the right of a nation to address itself as such. It was a potent combination of shared characteristics, identity, institutions and patriotism, more than merely what made the Scots Scottish, the French French, or the Germans German. Nationality was not only what made a nation a nation, it was also what made a nation great – at least in its own eyes. Nationality signified a set of shared national characteristics and an inherited sense of identity, yet it was also a virtue in and of itself, both for the individual and for the nation as a whole.

At a time when the Union between Scotland and England is once again under the spotlight, Remembering the Past in Nineteenth-Century Scotland examines the way in which Scotland’s national heroes were once remembered as champions of both Scottish and British patriotism. Whereas 19th-century Scotland is popularly depicted as a mire of sentimental Jacobitism and kow-towing unionism, this book shows how Scotland’s national heroes were once the embodiment of a consistent, expressive and robust view of Scottish nationality. Whether celebrating the legacy of William Wallace and Robert Bruce, the reformer John Knox, the Covenanters, 19th-century Scots rooted their national heroes in a Presbyterian and unionist view of Scotland’s past. Examined through the prism of commemoration, this book uncovers collective memories of Scotland’s past entirely opposed to 21st-century assumptions of medieval proto-nationalism and Calvinist misery. Detailed studies of 19th-century commemoration of Scotland’s national heroes Uncovers an all but forgotten interpretation of these ‘great Scots’ Shines a new light on the mindset of nineteenth-century Scottish national identity as being comfortably Scottish and British Overturns the prevailing view of Victorian Scottishness as parochial, sentimental tartanry

William Wallace is one of Scotland’s most enduring national heroes. Since the 1470s and the first appearance of Blind Harry’s epic poem, The Actes and Deidis of the Illustre and Vallyeant Campioun Schir William Wallace, Wallace has occupied a central place in the collective memory of the Scots, a position he continues to hold, thanks in part to the enormous success of the 1995 film Braveheart. One of the reasons for Wallace’s enduring appeal is the simplicity of his story. Born as a commoner, urged on by his love of liberty and need to free Scotland from the chains and slavery of an oppressive neighbour, Wallace rose through the ranks of society to become Guardian of Scotland. He went on to lead the Scots to victory over the armies of the tyrannical English king, Edward I, at Stirling Bridge. Whilst attempting to place Scotland’s hard-fought independence on a more secure footing, Wallace was defeated, betrayed, and taken to London for trial and execution. In essence, this was the hero’s journey: from relatively lowly stock to victory, martyrdom, and permanent, illustrious memory.

Photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopies have been carried out at 6 K on the ∼1540 nm 4I13/2–4I15/2 emissions of Er3+ in Er-implanted and annealed GaN. These studies revealed the existence of multiple Er3+ centers and associated PL spectra in Er-implanted GaN films grown by metalorganic chemical vapor deposition, hydride vapor phase epitaxy, and molecular beam epitaxy. The results demonstrate that the multiple Er3+PL centers and below-gap defect-related absorption bands by which they are selectively excited are universal features of Er-implanted GaN grown by different techniques. It is suggested that implantation-induced defects common to all the GaN samples are responsible for the Er site distortions that give rise to the distinctive, selectively excited Er3+PL spectra. The investigations of selectively excited Er3+PL and PLE spectra have also been extended to Er-implanted samples of Mg-doped GaN grown by various techniques. In each of these samples, the so-called viol...

The incorporation of intentional strain in heterostructure lasers was almost unheard of a decade ago or so and considered a problem to be avoided. Advances in both epitaxial crystal growth technology and the understanding of the physics and reliability of these materials have led to a remarkable increase in the commercial use of strained-layer lasers. The industry has benefited from an increase in the available range of emission wavelengths from quantum-well diode lasers and dramatic improvement in their time-zero performance. In the paper, we review the characteristics of strained-layer InGaAs quantum-well heterostructure lasers that have resulted in the emergence of this important technology.

The ion damage produced in alloys of AlxGa1−xAs (x = 0.6, 0.7, 0.8, and 0.85) by implantation at 77 K with Kr ions (500, 700, and 1500 keV) was studied by using Rutherford backscattering channeling and transmission electron microscopy. In addition, the accumulation of ion damage at 50 K was studied by performing the ion implantations in situ in the transmission electron microscope. In Al0.8Ga0.2As, damage accumulation at 77 K was independent of dose rate, indicating that dynamic annealing is not occurring at 77 K. The in situ studies demonstrated that planar defects are produced on warm-up from 50 K to room temperature, indicating that they are not the nucleation site for amorphization. The lower energy implantations revealed that amorphization initiated within the AlxGa1−xAs layer, showing that heterointerfaces are not required for amorphization. These results, along with the similarity of the room-temperature microstructures in the different alloys, imply that the amorphization mechanism is independent of Al content. It is proposed that the observed dependence of the amorphization dose on Al content is related to an increase in the number of cascade overlaps needed to initiate and to produce a continuous amorphous layer. A mechanism explaining the microstructural changes with composition, based on the thermal and physical properties of the alloy and on the distribution of energetic cascade events, is presented.

The distributed Bragg pulse shaper (DBPS) is a series of electrically switchable Bragg mirrors on a semiconductor waveguide. The DBPS encodes data packets using parallel electrical signals to set the states of the Bragg mirrors. A broad-band source pulse then probes the device to generate a high bandwidth serial wavepacket from the train of partially reflecting mirrors. This paper describes a DBPS constructed in AlGaAs. Using this device and a mode-locked Ti:sapphire laser, we create a 4-bit packet with 0.37 Tb/s burst bit rate and are demonstrate for the first time that bits in the wavepacket can be switched by electrical modulation of individual Bragg segments. We also describe a model collaborating the observed data.

Photoluminescence (PL) and photoluminescence excitation (PLE) spectroscopy have been carried out at 6K on the 1540 nm 4I13/2 → 4I15/2 emission of Er3+ in in situ Er-doped and Erimplanted GaN grown by hydride vapor phase epitaxy (HVPE). The PL and PLE of these two different Er-doped HVPE-grown GaN films are compared with Er-implanted GaN grown by metal organic chemical vapor deposition (MOCVD).In the in situ Er-doped HVPE-grown GaN, the lineshape of the broad PLE absorption bands and the broad PL bands is similar to that in Er-doped glass. The PL spectra of this in situ Er-doped sample are independent of excitation wavelength, unlike the PL of the Er-implanted GaN. These PL spectra are quite different from the site-selective PL spectra observed in the Er-implanted GaN, indicating that the seven different Er3+ sites existing in the Er-implanted MOCVD-grown GaN are not observed in the in situ Er-doped HVPE-grown GaN. Four of the seven different Er3+ sites observed in the Er-implanted MOCVD-grown GaN annealed at 900°C under a flow of N2 are present in the Er-implanted HVPE-grown GaN annealed at 800°C in an NH3/H2 atmosphere.

We investigate the relative validity of the Bruggeman effective-medium approximation and several alloy models to describe interfaces in the analysis of spectroscopic ellipsometric data of laminar samples, using data obtained on an Al x Ga 1− x As multilayer sample fabricated specifically for this purpose. The investigation highlights the types of errors that result from the use of inappropriate models. Optimum results are obtained with the alloy model where the graded-composition regions are approximated with multilayer stacks.

We have developed a novel structure for achieving high-brightness output from a semiconductor laser array using coherent spatial beam combination. The structure consists of an array of curved ridge waveguides with in-phase, coherent output. Interference of the multiple outputs leads to a narrow, bright, on-axis, far-field beam shape. Experimental results demonstrate a diffraction limited output beam width, ideal for high-brightness applications.

In this work, we have created a new type of structure, the nanopore active layer, for achieving quantization of carrier states in a semiconductor. The nanopore structure consists of a periodic two-dimensional array of localized energy barriers perturbing an otherwise conventional quantum well. This perturbation leads to the formation of intraband forbidden energy gaps which are observed experimentally.