Two color optical pumping, both above (anti-Stokes pump or ASP) and below (Stokes pump) the lasing wavelength, was adopted to reduce the net quantum defect (QD) in a solid-state Yb-doped fiber laser. The reduction in QD was achieved by converting a substantial portion of the gain medium's phonons directly into useful photons through a dual-wavelength excitation (DWE) mechanism. Since this is achieved through the usual processes of absorption and stimulated emission associated with lasing, high efficiency can be maintained. Both time domain and power measurements are presented, demonstrating a 13.2% reduction of the system's net QD and a 13.8% reduction in the lasing threshold power. These values were limited only by the available ASP power. Laser slope efficiency, with respect to launched ASP power, was found to be as high as 38.3%. A finite difference time domain model, developed to elucidate the role of both pumps in populating the upper states, corroborated the experimental findings. The DWE concept proposed here opens the door to an “excitation-balanced” type of self-cooled fiber laser. Simulation results also suggest that the technique is scalable and conceptually applicable to other solid-state laser systems.

The enduring contributions of low temperature plasmas to both technology and science are largely a result of the atomic, molecular, and electromagnetic (EM) products they generate efficiently such as electrons, ions, excited species, and photons. Among these, the production of light has arguably had the greatest commercial impact for more than a century, and plasma sources emitting photons over the portion of the EM spectrum extending from the microwave to soft X-ray regions are currently the workhorses of general lighting (outdoor and indoor), photolithography for micro- and nano-fabrication of electronic devices, disinfection, frequency standards (atomic clocks), lasers, and a host of other photonic applications. In several regions of the EM spectrum, plasma sources have no peer, and this article is devoted to an overview of the physics of several selected plasma light sources, with emphasis on thermal arc and fluorescent lamps and the more recently-developed microcavity plasma lamps in the visible and ultraviolet/vacuum ultraviolet (VUV) regions. We also briefly review the physics of plasma-based metamaterials and plasma photonic crystals (PPCs) in which low temperature plasma tunes the EM properties of filters, resonators, mirrors, and other components in the microwave, mm, and sub-mm wavelength regions.

Several Förster resonance energy transfer (FRET) lasers have been realized by employing the robust and versatile streptavidin-biotin (SPB) biocomplex as the acceptor–donor linkage. SPB offers a fixed acceptor–donor separation (“ruler”) of <6 nm, which lies within the Förster radius for a broad range of donors and acceptors. A Cy3-SPB-Cy5 conjugate laser (where Cy3 and Cy5 are cyanine dyes) peaking at λ ∼ 708 nm has been observed, and its bandwidth and threshold pump energy (at 532 nm) have been measured to be ∼4.5 nm and 118 µJ (corresponding to a pump energy density of 179 ± 5 µJ/mm2), respectively. Depolarization of the linearly polarized pump optical field by this FRET process is found to be <12%. To tether the acceptor and donor, the SPB complex requires only that either be conjugated, thereby allowing FRET processes to be examined among an extensive set of biomolecules, inorganics, and nanoantenna acceptors, for example. As a result, fluorophore-nanoparticle lasers having characteristics of both FRET lasers and plasmonic emitters have been demonstrated. Laser spectra and the phase shift induced by a 10 or 100 nm gold nanoparticle tethered to the Cy3-SPB complex suggest that both the fluorescent protein and nanoparticle are able to act as an acceptor. The brightness associated with this new class of fluorophore/nanostructure FRET lasers will broaden the scope of accessible biomedical diagnostics, including cellular imaging and the detection of DNA and proteins.

Stimulated molecular Raman scattering has been observed in KXe, a transient molecule having a dissociative ground state. The quantum efficiency for this nonlinear process is >99%.

A novel excitation balanced laser is proposed, where introducing a second pump, to the red of the signal wavelength, significantly reduces the quantum defect (QD). Experimental and theoretical results indicate near-zero QD heating is possible.