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Distributed Feedback Lasing from Arbitrary Gain Morphologies
- Author(s)
- UMAR MUHAMMAD
- Advisor
- Sunghwan Kim
- Department
- 일반대학원 에너지시스템학과
- Publisher
- The Graduate School, Ajou University
- Publication Year
- 2020-08
- Language
- eng
- Alternative Abstract
- This thesis discusses the use of the organic distributed feedback (DFB) lasers for single mode lasing from arbitrary gain morphologies. Because in the typical DFB laser the use of uniform gain media with the thickness of few hundred itself acts as a resonators to induce and guide DFB modes, which puts the limits on their applications to obtain lasing from irregular shaped gain media, such as dye-staining cells and tissues. Therefore, in the first project, we report a reusable second order Bragg grating template to induce a single mode DFB emission from variety of the states of gain media. The entire DFB structure composes of a slightly thin (25 nm) and disconnected titanium dioxide (TiO2) layer deposited on a one-dimensional (1D) quartz grating surface. The use of optically thick casted and thin coated film, a free-standing thick film and optically active liquid as external gain media yields single mode DFB emission from the same template with reliable performance. Numerical simulations confirms that the thin and disconnected TiO2 grating pattern support and strongly confines DFB mode even under no index difference between superstrate and substrate. Additionally, the template shows high sensitivity and detection limit for refractometric sensing when there is no typical DFB laser waveguide. In the second project we focus on the arbitrary patterning of the photonic components via inkjet printing method to emit and guide light from printed photonic components on a same DFB board (TiO2 deposited DFB board presented in previous section). Inkjet printing is a simple, cost-effective, and environment friendly patterning technique which works beyond the use of heat, UV radiations, and plasma. Therefore, this technique is more suitable for patterning the biomaterials because biofunctionality and bioactivity remains preserved during the patterning process. However, patterning of the biomaterials based soft photonic devices by inkjet printing technology is still challenging because preciseness and uniformity of the device requires to control photons at nanoscale efficiently. This study shows inkjet printing of silk protein photonic components on a single DFB board to emit/guide single mode DFB lasing. A DFB board containing a quartz grating surface coated with a thin TiO2 layer enables coherent feedback of the generated photons from arbitrary silk pattern printed on it. A minimum silk pattern with the diameter of 200 µm can lase under optical pumping. The addition of gold nanoparticles in the silk/dye solution can tune the resonance position to the required wavelength. Furthermore, lasing and waveguiding photonic components can be drawn on a single DFB board to extract the emitted lasing light. The printed components can be restructured by post modification (water-removal and reprinting). In addition, the use of the optically absorptive melanin nanoparticles placed on the printed waveguides can attenuate the propagating lasing signal, which confirms the photonic circuit have potential for the sensing applications. The third project deals with the study of the typical DFB laser with a thin spin-coated gain morphology (optical waveguide) layer onto the quartz grating surface to yield a physically transient and eco-friendly chemosensor. In the organic DFB lasers, quenching the quantum efficiency of the probe dye under multiple optical pumping puts the limit on the life time of the laser. Such laser with short life span can be used for chemosensing applications. Here, we report the usefulness of such organic DFB lasers with short life-time, by spin-coating a solution of natural silk protein and sodium fluorescein probe dye on the reusable quartz grating surface to yield a physically transient, low-cost, and eco-friendly DFB laser chemosensor. The prepared DFB laser shows high sensitivity towards hydrochloric (HCl) acid vapor by attenuating its optical response. The sensitivity of the DFB laser chemosensor depends on the concentration of the HCl acid vapors and the thickness of the silk/dye optical gain layer. Moreover, physically transient DFB laser chemosensor shows its response to HCl vapor 30 time higher than obtained from fluorescence chemosenseor. Additionally, used silk/dye layer can be easily removed by water washing and new laser sample can be prepared by recoating new solution on the quartz grating.
- Fulltext
- Appears in Collections:
- Graduate School of Ajou University > Department of Energy Systems > 4. Theses(Ph.D)
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