Angular dependent light emission from planar waveguides

Journal Article · Wed Jan 07 00:00:00 EST 2015 · Journal of Applied Physics

DOI:https://doi.org/10.1063/1.4905011· OSTI ID:22399231

Peter, Jaison ^[1]; Prabhu, Radhakrishna ^[2]; Radhakrishnan, P.; Vallabhan, C. P. G.; Nampoori, V. P. N.; Kailasnath, M. ^[1]

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1. International School of Photonics, Cochin University of Science and Technology, Cochin 682022 (India)
2. CRE"+E, IDEAS Research Institute, Robert Gordon University, Aberdeen AB10 7GJ (United Kingdom)

We have investigated the angular dependence of amplified spontaneous emission (ASE) and laser emission from an asymmetric and free-standing polymer thin films doped with rhodamine 6G, which is transversely pumped by a pulsed Nd:YAG laser. A semi-leaky waveguide or quasi-waveguide structure has been developed by spin coating technique. In these waveguides, the light was confined by the film/air-film/glass substrate interfaces. At the film/substrate interface, a portion of light will reflect back into the film (guided mode) and the remaining refracted to the substrate resulting in cutoff modes. A blue-shift in ASE has been observed when the pump power was increased from 8 to 20 mW allowing a limited range of tuning of emission wavelength. To study the directionality of the ASE from the waveguide, we have measured the output intensity and FWHM of emission spectra as a function of viewing angle (θ) from the plane parallel to film. From the detailed examination of the output emission spectra, as +θ increases from 0° there has been an initial decrease in output intensity, but at a particular angle ≈10° an increase in output intensity was observed. This additional peak in output intensity as +θ is a clear indication of coexistence of the cutoff mode. We also present a compact solid-state laser based on leaky mode propagation from the dye-doped polymer free-standing film (∼50 μm thickness) waveguide. The partial reflections from the broad lateral surfaces of the free-standing films provided the optical feedback for the laser emission with high directionality. For a pump power of 22 mW, an intense line with FWHM <0.2 nm was observed at 578 nm.

• OSTI ID: 22399231
• Journal Information: Journal of Applied Physics, Vol. 117, Issue 1; Other Information: (c) 2015 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA); ISSN 0021-8979
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
75 CONDENSED MATTER PHYSICS
SUPERCONDUCTIVITY AND SUPERFLUIDITY
AIR
ASYMMETRY
DOPED MATERIALS
EMISSION SPECTRA
GLASS
INTERFACES
NEODYMIUM LASERS
POLYMERS
REFLECTION
RHODAMINES
SPIN-ON COATING
SUBSTRATES
SURFACES
THICKNESS
THIN FILMS
VISIBLE RADIATION
WAVEGUIDES