InLight Solutions (United States)

Early studies suggest that absorption coefficient of GaN exceeds 100 cm−1 at wavelengths below 380 nm, indicating GaN might not be suitable as a waveguide (WG) material for laser diodes (LDs) in this range. However, in those studies, material defects (rather than GaN band edge absorption) could contribute significantly to the measured absorption loss. In this work, III-Nitride LDs emitting at 376 nm using unintentionally doped GaN WG was demonstrated for high-power operation. Devices with a cavity length of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$750 \; \mu $ </tex-math></inline-formula>m and a ridge width of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$10 \; \mu $ </tex-math></inline-formula>m exhibited a threshold current of 625 mA and a slope efficiency of 1.13 W/A under pulsed conditions. The highest output power of 3.4 W was obtained at an injection current of 3.5 A. These promising results suggest that GaN band edge absorption may not be as significant at 376 nm or even shorter wavelengths, allowing more flexibility in epitaxial design.

Stability of high-concentration protein formulationsis considereda major challenge in current biopharmaceutical development. In thiswork, we introduce laser-based mid-infrared (IR) spectroscopy as aversatile technique to study the effect of protein concentration andpresence of sugars on the thermal denaturation of the model proteinbovine serum albumin (BSA). Many analytical techniques struggle tocharacterize the complex structural transition that occurs duringprotein denaturation. To this end, a commercially available laser-basedmid-IR spectrometer equipped with a customized flow cell was employedto record IR spectra of BSA in the temperature range of 25–85°C. The temperature perturbation induces a conformational changefrom a native α-helical to an intermolecular β-sheet secondarystructure in BSA. Systematic investigation of the concentration dependenceof the α–β transition temperature between 30 and90 mg mL–1 shows a trend of decreasing denaturationtemperatures at higher BSA concentrations. In-depth chemometric analysisby a multivariate curve resolution-alternating least squares (MCR-ALS)analysis of the spectra, suggested the formation of not one but twointermediates in the denaturation of BSA. Subsequently, the impactof sugars on denaturation temperatures was investigated, revealingboth stabilizing (trehalose, sucrose, and mannose) and destabilizing(sucralose) effects, illustrating the applicability of this methodas an investigative tool for stabilizers. These results highlightthe potential and versatility of laser-based IR spectroscopy for analysisof protein stability at high concentrations and varying conditions.

Mid-infrared spectroscopy is one of the major analytical techniques employed for measurements of protein structure in solution. Traditional Fourier Transform-Infrared (FT-IR) measurement is limited by its blackbody light source that is inherently spatially incoherent and has low optical power output. This limitation is pronounced when working with proteins in aqueous solutions. Strong absorbance of water in protein amide I region 1600-1700cm-1 restricts light path length to <10μm and imposes significant experimental challenges in sample and flow cell handling. Emerging laser spectroscopic techniques use high-power coherent laser as light source that overcomes the limitation in FT-IR measurement. In this study, we employed an innovative infrared spectrometer that uses quantum cascade laser (QCL) as light source. Continuous infrared radiation from this laser source can be swiftly swept within the amide I region (1600-1700cm-1) and amide II region (1500-1600cm-1), which makes this technique ideal for protein secondary structure study. Protein solutions as low as 0.5mg/mL were measured rapidly without any sample preparation. Infrared spectra of model proteins were thus collected, and a chemometric model based on partial least squares regression was developed to quantify α-helix and β-strand motifs in protein secondary structure. The model was applied to measurement of the native secondary structure of commercial therapeutic proteins and bovine serum albumin (BSA) and in thermal degradation studies.

We demonstrate the analysis of ~1 µm contamination with high signal-to-noise in a simultaneous infrared and Raman microscope at the same time, at the same location and at submicron spatial resolution. This combined technique provides high sensitivity to small sample volumes without melting or damaging the samples by using separate infrared excitation and visible laser detection mechanisms. The measurement process does not involve physically contacting the sample, hence simplifying sample preparation and avoiding cross-contamination between sample changes. To showcase this new capability, we provide examples from the contamination in the gap between a solder joint and a non-wetting pad, adhesive residues on a glass panel and foreign matter near a copper post. Such challenges could not be readily resolved with conventional FTIR and Raman techniques. The simultaneous O-PTIR and Raman brings complementary and confirmatory results to analysis previously thought to be difficult to impossible.

We report on a new class of turnkey liquid analyzers powered by tunable mid-IR quantum cascade lasers. These analyzers offer excellent chemical selectivity, speed and sensitivity in a variety of applications from water quality assessment to biopharmaceutical process monitoring. We will discuss the theory of operation of these new instruments and provide relevant application examples.

Quantum Cascade Laser (QCL) spectroscopic imaging is a novel technique with many potential applications to histopathology. Like traditional Fourier Transform Infrared (FT-IR) imaging, QCL spectroscopic imaging derives biochemical data coupled to the spatial information of a tissue sample, and can be used to improve the diagnostic and prognostic value of assessment of a tissue biopsy. This technique also offers advantages over traditional FT-IR imaging, specifically the capacity for discrete frequency and real-time imaging. In this work we present applications of QCL spectroscopic imaging to tissue samples, including discrete frequency imaging, to compare with FT-IR and its potential value to pathology.

Daylight Solutions has pioneered the development and commercialization of quantum cascade laser (QCL) technology for commercial and military markets. Multi-Watt, multi-wavelength QCL-based systems have been manufactured and tested against harsh military environmental requirements for military applications. These self-contained, turn-key systems have been designed to comply with modular open system architecture (MOSA) principles, and have been proven in several different system geometries. This paper will highlight the environmental requirements imposed upon, and performance from, QCL-based laser systems for example military applications.

We present our recent development of short wavelength quantum cascade lasers (QCLs) made of strain balanced GaxIn1-xAs/AlyIn1-yAs material on InP substrates. We demonstrate room temperature continuous-wave (CW) lasing of the fundamental lateral mode at four wavelengths of 4.6, 4.0, 3.8, and 3.5 μm. We obtained 60-mW CW output power at 10 °C and 3.55-μm wavelength, which is the shortest CW lasing wavelength demonstrated at room temperature by a QCL, to the best of our knowledge. We also performed a life test on λ = 4.6 μm QCL chips. To date, we have accumulated the life test data for more than 11 000 and 4100 h under two aging conditions, 20°C and 0.85-A constant current, and 60°C and 1-A constant current, respectively.

Amplitude modulated photo-acoustic spectroscopy using a 10.4 μm EC-QCL source, targeting the NH3 absorption line at 965.35 cm-1, resulted in a sub-ppb ammonia detection limit. Atmospheric ammonia concentration levels from our study will be reported.

We present the design and performance of a novel broadly tunable continuous-wave external-cavity interband cascade laser (ECicL). The ICL die growth and fabrication, as well as the external cavity geometry are described. Tuning across the 3.2-3.35 microm wavelength range, limited by the gain width of the ICL active medium, is achieved at a maximum power level of 4 mW.