Re-evaluation of all-plastic organic dye laser with DFB structure fabricated using photoresists

Abstract

Organic solid-state lasers (OSSLs) with distributed feedback structures can detect nanoscale materials and therefore offer an attractive sensing platform for biological and medical applications. Here we investigate the lasing characteristics, i.e., the threshold and slope efficiency, as a function of the grating depth in OSSL devices with distributed feedback (DFB) structure fabricated using photoresists. Two types of photoresists were used for the DFB structures: a negative photoresist, SU-8 2002, and a positive photoresist, ma-P 1275. The DFB structure was fabricated using a Lloyd-mirror configuration. The active layer was a rhodamine 6G-doped cellulose acetate waveguide. The threshold for the first order mode (m = 1) was lower than that for the second and third order modes (m = 2, and 3). A low threshold of 27 μJ cm−2 pulse−1 (58 nJ) was obtained using SU-8 2002, with m = 1. The slope efficiency was evaluated as a function of grating depth for each mode and increased as the grating depth increased.

An Efficient and Color‐Tunable Solution‐Processed Organic Thin‐Film Laser with a Polymeric Top‐Layer Resonator

“…Therefore, a lower threshold would be expected for the R T architecture, with respect to that of Std and R B , with a larger different in the latter case. In fact in previous studies, R B ‐type lasers showed larger thresholds (typically by one order of magnitude or more) than Std‐type ones, as a result of the low refractive index contrast between the active film and the resonator layer.…”

“…The lowest values (<1 kW cm −2 ) have been achieved with lasers whose DFB gratings are engraved on conventional inorganic substrates (e.g., glass or SiO 2 ), onto which the active films are deposited (this configuration will henceforth be denoted as standard; Std). Other studies, aimed at improving device integration, reducing device costs, and achieving mechanical flexibility, have focused either on architectures with gratings imprinted directly on the active film, or on systems wherein both the active material and the resonator, which is generally located below the active film and only in few cases on top of it, were processed from solution. Unfortunately, the thresholds of these solution‐processed lasers are generally high (>8 kW cm −2 ), except for few exceptions .…”

Carbon‐Bridged p‐Phenylenevinylene Polymer for High‐Performance Solution‐Processed Distributed Feedback Lasers

“…Typical state‐of‐the‐art organic DFB lasers have shown pump thresholds of <1 kW cm −2 , traditionally with the gratings engraved into conventional inorganic substrates (e.g., SiO 2 ), onto which the active film is deposited . Efforts aiming at reducing device costs and improving mechanical flexibility have focused on architectures with gratings imprinted directly on the active film (e.g., thermal or solvent imprinting), or devices wherein both the active material and the resonator can be processed from solution (such as UV‐nanoimprint lithography (UV‐NIL)) . Recently, an important landmark was the demonstration of lasers with high efficiency, low threshold, long operational lifetime, and broad wavelength tunability in a single device, thanks to the combination of highly efficient and photostable dyes and a not very common DFB resonator configuration .…”

An Efficient All‐Plastic Organic Waveguide Solid‐State Laser Devices with Distributed Bragg Reflector

“…Excitation laser energy reflected by a half‐mirror was monitored using an Ophir photodiode‐type pyrometer PD10 with Nova II Display. Lasing beam energy emitted from the edge of the waveguide was monitored by an optical fiber coupled photodiode pyrometer (Ophir PD‐10‐PJ with Nova II Display) equipped with an optical filter to cut an exciting beam in front . The index of refraction ( n ) of the waveguide was measured using a prism coupling method, in which the evanescent wave penetrates into the waveguide layer at the specific mode angle at each mode ( m =0, 1, 2….)…”

“…The slope efficiency of 4.7% was achieved for the DFB waveguide device with 3.4 µm thickness active layer with high refractive intermediate layer . The effect of grating depth of DFB resonator on the slope efficiency and the lasing threshold is evaluated: deeper grating depth of DFB structure leads to the higher slope efficiency . In recent paper, we reported the slope efficiency between 4.9 and 10% for a tris(8‐quinolinolato)aluminum (Alq 3 )/4‐(dicyanomethylene)‐2‐methyl‐6‐(4‐dimethylaminostyryl)‐4H‐pyran (DCM) host‐guest system in which the fluorescence resonance energy transfer or Förster resonance energy transfer (FRET) assist the energy migration .…”