Angular dependent light emission from planar waveguides

Abstract

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.

Blueshift Plasmonic effect in photonic crystal cavity with gold nano-structure

“…Colloidal based self-assembly lm wasexcited by laser radiation, the probability of radiative transition increases at higher energy edge of the spectrum, creating a blue shift in the recorded spectrum [40], while enhancing the pump power from 50 to 275 mW. It indicates that the laser powers affect the peak broadening and peak shift [41], as has been shown in g. 3.…”

Naturally Degradable Photonic Devices with Transient Function by Heterostructured Waxy‐Sublimating and Water‐Soluble Materials

“…The spatial profile for ASE (Figure 3e) evidences the coexistence of different light modes which are out‐coupled, which is typical of asymmetric emissive layers embedding organic layers with optical gain. [ 22 ] Furthermore, the device photostability in air is studied by recording spectra of the emitted light as a function of the number of excitation pulses (i.e., time), at a constant pump fluence of 0.3 mJ cm −2 (Figure 3f). The operational lifetime of the device (given by the number of excitation pulses at which the ASE intensity decays by 1/ e ) is so estimated to correspond to about 1.5 × 10 3 pulses, with a FWHM increasing by a factor 1.5 in a related way (Figure 3g).…”