Active laser medium

About: Active laser medium is a research topic. Over the lifetime, 9874 publications have been published within this topic receiving 134002 citations. The topic is also known as: Laser medium, lasing medium.

Plasmon lasers at deep subwavelength scale

Abstract: Hybrid plasmonic waveguides are described that employ a high-gain semiconductor nanostructure functioning as a gain medium that is separated from a metal substrate surface by a nanoscale thickness thick low-index gap. The waveguides are capable of efficient generation of sub-wavelength high intensity light and have the potential for large modulation bandwidth >1 THz.

Demonstration of a spaser-based nanolaser

Abstract: Nanoplasmonics — the nanoscale manipulation of surface plasmons (fluctuations in the electron density at a metallic surface) — could revolutionize applications ranging from sensing and biomedicine to imaging and information technology. But first, we need a simple and efficient method for actively generating coherent plasmonic fields. This is in theory possible with the spaser, first proposed in 2003 as a device that generates and amplifies surface plasmons in the same way that a laser generates and amplifies photons. Now Noginov et al. present the first unambiguous experimental demonstration of spasing, using 44-nm diameter nanoparticles with a gold core and dye-doped silica shell. The system generates stimulated emission of surface plasmons in the same way as a laser generates stimulated emission of coherent photons, and has been used to implement the smallest nanolaser reported to date, and the first operating at visible wavelengths. Nanoplasmonics promises to revolutionize applications ranging from sensing and biomedicine to imaging and information technology, but its full development is hindered by the lack of devices that can generate coherent plasmonic fields. In theory, this is possible with a so-called 'spaser' — analogous to a laser — which would generate stimulated emission of surface plasmons. This is now realized experimentally, and should enable many new technological developments. One of the most rapidly growing areas of physics and nanotechnology focuses on plasmonic effects on the nanometre scale, with possible applications ranging from sensing and biomedicine to imaging and information technology1,2. However, the full development of nanoplasmonics is hindered by the lack of devices that can generate coherent plasmonic fields. It has been proposed3 that in the same way as a laser generates stimulated emission of coherent photons, a ‘spaser’ could generate stimulated emission of surface plasmons (oscillations of free electrons in metallic nanostructures) in resonating metallic nanostructures adjacent to a gain medium. But attempts to realize a spaser face the challenge of absorption loss in metal, which is particularly strong at optical frequencies. The suggestion4,5,6 to compensate loss by optical gain in localized and propagating surface plasmons has been implemented recently7,8,9,10 and even allowed the amplification of propagating surface plasmons in open paths11. Still, these experiments and the reported enhancement of the stimulated emission of dye molecules in the presence of metallic nanoparticles12,13,14 lack the feedback mechanism present in a spaser. Here we show that 44-nm-diameter nanoparticles with a gold core and dye-doped silica shell allow us to completely overcome the loss of localized surface plasmons by gain and realize a spaser. And in accord with the notion that only surface plasmon resonances are capable of squeezing optical frequency oscillations into a nanoscopic cavity to enable a true nanolaser15,16,17,18, we show that outcoupling of surface plasmon oscillations to photonic modes at a wavelength of 531 nm makes our system the smallest nanolaser reported to date—and to our knowledge the first operating at visible wavelengths. We anticipate that now it has been realized experimentally, the spaser will advance our fundamental understanding of nanoplasmonics and the development of practical applications.

High power fiber lasers: current status and future perspectives [Invited]

Abstract: The rise in output power from rare-earth-doped fiber sources over the past decade, via the use of cladding-pumped fiber architectures, has been dramatic, leading to a range of fiber-based devices with outstanding performance in terms of output power, beam quality, overall efficiency, and flexibility with regard to operating wavelength and radiation format. This success in the high-power arena is largely due to the fiber’s geometry, which provides considerable resilience to the effects of heat generation in the core, and facilitates efficient conversion from relatively low-brightness diode pump radiation to high-brightness laser output. In this paper we review the current state of the art in terms of continuous-wave and pulsed performance of ytterbium-doped fiber lasers, the current fiber gain medium of choice, and by far the most developed in terms of high-power performance. We then review the current status and challenges of extending the technology to other rare-earth dopants and associated wavelengths of operation. Throughout we identify the key factors currently limiting fiber laser performance in different operating regimes—in particular thermal management, optical nonlinearity, and damage. Finally, we speculate as to the likely developments in pump laser technology, fiber design and fabrication, architectural approaches, and functionality that lie ahead in the coming decade and the implications they have on fiber laser performance and industrial/scientific adoption.

Stimulated emission in a periodic structure

Abstract: We have investigated laser oscillation in periodic structures in which feedback is provided by backward Bragg scattering These new laser devices are very compact and stable as the feedback mechanism is distributed throughout and integrated with the gain medium Intrinsic to these structures is also a gratinglike spectral filtering action We discuss periodic variations of the refractive index and of the gain and give the expression for threshold and bandwidth Experimentally we have induced index periodicities in gelatin films into which rhodamine 6G was dissolved The observed characteristics of laser action in these devices near 063 μm are reported

PT-symmetric laser absorber

Abstract: In a recent work, Y. D. Chong et al. [Phys. Rev. Lett. 105, 053901 (2010)] proposed the idea of a coherent perfect absorber (CPA) as the time-reversed counterpart of a laser, in which a purely incoming radiation pattern is completely absorbed by a lossy medium. The optical medium that realizes CPA is obtained by reversing the gain with absorption, and thus it generally differs from the lasing medium. Here it is shown that a laser with an optical medium that satisfies the parity-time $(\mathcal{PT})$ symmetry condition $\ensuremath{\epsilon}(\ensuremath{-}\mathbf{r})={\ensuremath{\epsilon}}^{*}(\mathbf{r})$ for the dielectric constant behaves simultaneously as a laser oscillator (i.e., it can emit outgoing coherent waves) and as a CPA (i.e., it can fully absorb incoming coherent waves with appropriate amplitudes and phases). Such a device can thus be referred to as a $\mathcal{PT}$-symmetric CPA laser. The general amplification or absorption features of the $\mathcal{PT}$ CPA laser below lasing threshold driven by two fields are determined.