Organic Photonic Crystal Lasers Research Articles

Simulation of 1D edge-emitting organic photonic crystal lasers based on conjugated polymer

A 1D edge-emitting organic semiconductor photonic crystal laser is designed and demonstrated based on conjugated polymer MEH-PPV as the gain medium. The bandgap and band-edge effect of photonic crystals are applied to construct an organic resonant cavity as the high reflective mirror and output coupler. Besides, the photonic crystal with a defect is introduced as the mode-selector inside the cavity to achieve the single longitudinal mode output. The simulation results show the edge-emitting laser outputs signals at the wavelength 588 nm with the full width at half maximum of 0.131 nm. All photonic crystal components of lasers are integrated on an organic ridge waveguide, which makes it compact and reliable for the potential application in all-optics integration in future.

Emission characteristics of near‐ultraviolet two‐dimensional organic photonic crystal lasers

AbstractWe demonstrate near‐ultraviolet frequency two‐dimensional organic‐photonic‐crystal laser using resonator structures that offer two‐dimensional distributed feedback at room temperature. The gain medium is N,N′‐di‐1‐naphthyl‐N, N′‐diphenylbenzidine (NPB) which is deposited on lithographically patterned silica structure. We observe surface emitting lasing action with the central beam normal to the surface and the far‐field emission characteristics of this laser. The devices operate in the blue spectral region, and exhibit very low threshold energies for oscillation (0.3 kW/cm2). The far field is also shown to contain information about the quality of the photonic crystal. This emission pattern offers a convenient and powerful way to evaluate the nature of laser action in such resonators. © 2007 Wiley Periodicals, Inc. Microwave Opt Technol Lett 50: 382–385, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/mop.23102

Lasing mechanisms in organic photonic crystal lasers with two-dimensional distributed feedback

We present a detailed experimental and theoretical investigation of the lasing characteristics of organic photonic crystal lasers. These lasers are based on strongly modulated two-dimensional polymer surface relief structures on which thin films of optically active organic materials have been deposited. We determine the in-plane photonic band structure of the corresponding quasiguided modes within an effective two-dimensional model. In addition, we calculate the total (three-dimensional) losses associated with these modes. This allows us to identify the lasing thresholds for square lattice geometries and to understand the emission pattern.

Enhanced feedback and experimental band mapping of organic photonic-crystal lasers

Photonic-crystal lasers whose feedback is enhanced by a thin layer of titanium dioxide (TiO2) have been experimentally investigated. The use of TiO2 increases the index contrast in the photonic crystal as well as the confinement in the waveguide, resulting in larger feedback of the lasing modes. This allows lower thresholds and much smaller devices. Vertically emitting laser devices, using the methyl-substituted ladder-type poly(p-phenylene) (MeLPPP) as gain material, have been fabricated according to optimized parameters, and the measured dispersion relation of the structures matches excellently with simulations. The devices feature a three to five times lower threshold than devices whose feedback structure is etched directly into the fused silica substrate.

Lasing action in two-dimensional organic photonic crystal lasers with hexagonal symmetry

We investigate fluorescence and lasing action from strongly modulated two-dimensional surface relief structures with hexagonal symmetry onto which thin films of optically active organic material have been deposited. As compared with second-order laser structures with square symmetry, these organic photonic crystal lasers exhibit unusual feedback mechanisms. As a result, we observe surface-emitting lasing action with a central beam normal to the surface and a hexagonal emission pattern of side-beams whose direction slightly deviates from the normal. A corresponding theoretical analysis allows us to determine the photonic bandstructure and the low-threshold laser modes in this system. These results agree very well with fluorescence data and confirm the hexagonal lasing pattern and the corresponding emission angles.

Enhancement of the mode coupling in photonic-crystal-based organic lasers

The mode coupling of organic photonic crystal lasers is enhanced by using a photonic crystal that consists of a thin layer of a high-index material. The high-index material increases the index contrast, the confinement in the waveguide and thus the mode coupling. Using such a photonic crystal gives rise to new design criteria. We investigate these criteria, and employ them in the design of an organic photonic crystal laser. Calculations of the coupling constant of the organic laser show that using high-index materials results in much higher coupling constants and thus smaller devices.

Directional lasing oscillation of two-dimensional organic photonic crystal lasers at several photonic band gaps

We fabricated a series of two-dimensional (2D) hexagonal organic photonic-crystal lasers whose lattice constant varies from 0.18 to 0.44 μm, and observed clear lasing oscillation at the four lowest band gap frequencies (M1, K2, M2, and Γ1). We used in-plane beam propagation analysis to clarify the 2D feedback mechanism at each gap frequency, which differs for different gaps. The observed K1 lasing oscillation is due to coupling of three nonparallel diffracted waves, which has a purely 2D character. This shows that photonic crystal lasers can operate with various feedback essentially different from that of conventional 1D distributed feedback lasers.

Emission characteristics of two-dimensional organic photonic crystal lasers fabricated by replica molding

We report on the far-field emission characteristics of two-dimensional photonic crystal-based organic waveguide lasers. The photonic crystals possess square vein, triangular, and honeycomb symmetries. The two-dimensional gratings are fabricated by employing soft lithographic methods. The far-field pattern that we observe is a result of out-of-plane diffractive coupling of the laser emission generated in the plane of the waveguide. This emission pattern offers a convenient and powerful way to evaluate the nature of laser action in such resonators. In devices which possess defects/breaks in the periodicity of the two-dimensional grating, laser emission generated in-plane is scattered in the plane of the waveguide. This phenomenon is the photonic crystal analogue of Kikuchi scattering in electronic crystals.