Far-Infrared Laser Emissions from Optically Pumped Methanol

The invention of the LASER (an acronym for Light Amplification by Stimulated Emission of Radiation) in 1960 came with no specific application in mind. Initially, some critics dubbed it “the solution in search of a problem.” It was only after the laser was invented that scientists and entrepreneurs found the laser’s real potential and created enormous amounts of applications spanning from technology used in everyday life to medical and defensive applications. At Central Washington University, an optically pumped molecular laser system is used to search for new sources of far-infrared radiation. The far-infrared region is loosely defined as light having wavelengths ranging from about 0.030 to 2.000 mm. With this experimental system, 71 far-infrared laser emissions were discovered using the methanol isotopologues 13CHD2OH, CH318OH, CHD2OH, and CH2DOH as the lasing medium. Additionally, several of these newly discovered laser emissions have been used to support the spectroscopic assignments of laser transitions previously proposed by other researchers. This presentation will outline the experimental system and method used in the search for new sources of far-infrared laser radiation along with a brief discussion of the experimental results and their role in performing spectroscopic assignments of molecular transitions. For his work on this project, Mark McKnight was nominated for the SOURCE 2014 Scholar of the Year Award. The presentation also received a College of the Sciences Best Oral Presentation Award for 2014

Advancing colloidal quantum dot photovoltaic technology

Colloidal quantum dots (CQDs) are attractive materials for solar cells due to their low cost, ease of fabrication and spectral tunability. Progress in CQD photovoltaic technology over the past decade has resulted in power conversion efficiencies approaching 10%. In this review, we give an overview of this progress, and discuss limiting mechanisms and paths for future improvement in CQD solar cell technology.We briefly summarize nanoparticle synthesis and film processing methods and evaluate the optoelectronic properties of CQD films, including the crucial role that surface ligands play in materials performance. We give an overview of device architecture engineering in CQD solar cells. The compromise between carrier extraction and photon absorption in CQD photovoltaics is analyzed along with different strategies for overcoming this trade-off. We then focus on recent advances in absorption enhancement through innovative device design and the use of nanophotonics. Several light-trapping schemes, which have resulted in large increases in cell photocurrent, are described in detail. In particular, integrating plasmonic elements into CQD devices has emerged as a promising approach to enhance photon absorption through both near-field coupling and far-field scattering effects. We also discuss strategies for overcoming the single junction efficiency limits in CQD solar cells, including tandem architectures, multiple exciton generation and hybrid materials schemes. Finally, we offer a perspective on future directions for the field and the most promising paths for achieving higher device efficiencies

New Far-Infrared Laser Emissions from Optically Pumped CH2DOH, CHD2OH, and (CH3OH)-O-18

An optically pumped molecular laser system utilizing a transverse or zig-zag pumping geometry of the far-infrared (FIR) laser medium has enabled the reinvestigation of the CH 2 DOH, CHD 2 OH, and CH 3 18 OH isotopic forms of methanol for wavelengths \u3e 100 μm. With this system, 28 FIR laser emissions have been discovered with wavelengths ranging from 117.2 to 744.7 μm. Along with the wavelength, each laser emission is reported with its optimal operating pressure, polarization with respect to the CO 2 pump laser, and relative intensity. Three of the laser emissions generated by CH 3 18 OH support the spectroscopic assignments of FIR laser transitions originally proposed through combination-difference loops. A fourth CH 3 18 OH laser emission should contribute to another, incomplete FIR laser scheme

Long-Cavity M-Plane GaN-Based Vertical-Cavity Surface-Emitting Lasers with a Topside Monolithic Curved Mirror

We report long-cavity (60.5 λ) GaN-based vertical-cavity surface-emitting lasers with a topside monolithic GaN concave mirror, a buried tunnel junction current aperture, and a bottomside nanoporous GaN distributed Bragg reflector. Under pulsed operation, a VCSEL with a 9 µm aperture had a threshold current density of 6.6 kA/cm2, a differential efficiency of 0.7%, and a maximum output power of 290 µW for a lasing mode at 411 nm and a divergence angle of 8.4°. Under CW operation, the threshold current density increased to 7.3 kA/cm2, the differential efficiency decreased to 0.4%, and a peak output power of 130 µW was reached at a current density of 23 kA/cm2

Metalation/De-metalation as a Post-Gelation Strategy to Tune the Mechanical Properties of Catenane-Crosslinked Gels

Mechanically interlocked molecules (MIMs) possess unique architectures and non-traditional degrees of freedom that arise from well-defined topologies that are achieved through precise mechanical bonding. Incorporation of MIMs into materials can thus provide an avenue to discover new and emergent macroscale properties. Here, the synthesis of a phenanthroline-based [2]catenane crosslinker and its incorporation into polyacrylate organogels is described. Specifically, Cu(I) metalation and de-metalation was used as a post-gelation strategy to tune the mechanical properties of a gel by controlling the conformational motions of integrated MIMs. The organogels were prepared via thermally initiated free radical polymerization, and Cu(I) metal was added in MeOH to pre-treated, swollen gels. De-metalation of the gels was achieved by adding cyanide salts and washing the gels. Changes in Young’s and shear moduli, as well as tensile strength, were quantified through oscillatory shear rheology and tensile testing. The reported approach provides a general method for post-gelation tuning of mechanical properties using metals and well-defined catenane topologies as part of a network architecture