Signal amplification at the polymer optical fiber low-loss window of 650 nm is reported in an SU8 rib waveguide coated with Rhodamine-640 doped poly(methyl methacrylate). A signal beam is end-fired into the facet of a 7×100μm waveguide and amplified by top pumping of the 2-μm-thick cladding region with a pulsed pump source focused into a 9-mm-long stripe. A gain of 14dB and a minimum signal-to-noise ratio of around 2 dB are achieved in a 15-mm-long device with a low threshold pump intensity of 0.25μJ∕mm2, which is an order of magnitude lower than previously reported.
We report optical signal amplification in a solid-state dye-doped polymer with a rib waveguide structure. A 625nm pulsed signal and a collinear 575nm pump are coupled into a 1μm×120μm poly(methyl methacrylate) waveguide doped with 1% by weight Rhodamine 640 dye. Depending on the signal intensity, a maximum optical gain in the 21–26dB range is obtained from a 1.2-cm-long device, accompanied by a signal-to-noise ratio in the 9–16dB range.
We report a study of the optical signal amplification properties of Rhodamine 640 in solution, in thin-film format dispersed within a poly(methyl methacrylate) (PMMA) polymer matrix, and in a waveguiding structure created by coating polymer-dispersed Rhodamine 640 onto a patterned quartz substrate. The optical signal amplification experiments were carried out using a collinear pump and signal setup. Depending on both pump and signal energies, gains of up to 41 dB were achieved in solution, while 1% by weight dye-doped PMMA films showed net gains of 54cm−1, and associated losses of 16cm−1. Using the same concentration dye/PMMA dispersions, waveguide structures were fabricated with a 120×1μm2 cross section and a length of 1.2 cm. The internal optical gain values measured at 625 and 650 nm were found to be as high as 26 and 8 dB, respectively. The corresponding signal-to-noise ratio was in the 7–21-dB range at 625 nm and in the 3–21-dB range at 650 nm. Both in solution and in the waveguide structures we found that amplified spontaneous emission had a detrimental effect on the optical gain characteristics through a decrease in the signal-to-noise ratio.
We demonstrate optical signal amplification in a solid-state dye-doped polymer with a rib waveguide structure. The device consists of a 1µm × 120µm poly(methyl methacrylate) (PMMA) waveguide, doped with 1% by weight Rhodamine 640 dye, spin coated onto a silica substrate. A 625nm pulsed signal and a co-linear 575nm pump are facet coupled into the waveguide and optical amplification of the signal is demonstrated. Depending on the signal intensity, a maximum internal gain in the 21-26dB range at 625nm is achieved using a 1.2cm long waveguide. The device exhibits a promising signal-to-noise ratio in the 9-16dB range and has the potential for tuning in a 40-50nm wavelength window with the same dye, and throughout the visible spectrum using other dyes. The wavelength operating range of this device is also analyzed. We therefore present a compact, easy to fabricate, high gain block suitable for use in conjunction with plastic optical fibers, which have a low-loss window at around 640nm. Since most of the optical amplification takes place in a short region (<10µm), an even more compact device geometry can be envisaged using a shorter waveguide.
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