Controlling Lasing Behavior Of Dye Laser By Guided Mode Resonance Structure

Dye lasers are organic lasers that use a pulsed or continuous light source as the pump source with a certain organic dye dissolved in a certain solvent as the gain medium.The dye lasers have the characteristics of small size,high integration,high output power,and a wide tuning range.Thus they are very promising in the research field of agricultural detection,air quality detection,medical cosmetology,and the aviation industry.One or two-dimensional photonic crystal structures are usually used to construct periodic resonators in dye lasers in order to achieve tunable characteristics of the emitted laser.The subwavelength grating based on the guided-mode resonance effect is a new kind of diffractive optical element,which has the characteristics of high reflection efficiency,high diffraction efficiency,and tunable resonance wave peak in a wide spectral range.It is widely used in a series of optical elements such as color filters and optical sensors.When the guided-mode resonance occurs,it will enhance local electromagnetic field energy inside the waveguide structure,which can be applied to lengthen the interaction time between light and matter,such as up-conversion luminescence,quantum dot luminescence,and various types of lasers.In this paper,the reflective and transmissive dye laser models are constructed based on the guided-mode resonant grating structure.The laser emission is enhanced by using the local electromagnetic field energy inside the waveguide structure during resonance excitation.Firstly,a dye laser is designed based on a guided-mode resonance structure embedded with double waveguide layers.A four-layer film is designed between the substrate and the grating that the refractive index is low-high-low-high from top to bottom.The laser dye doping polyurethane was used in the low-RI materials,while tantalum pentoxide was used in the high-RI materials.The structure supports two GMR wavelengths that precisely correspond to the laser dye's absorption and emission peaks by selecting the structure parameters.The enhancement of the lasing emission is achieved by matching both the absorption and emission wavelength of the laser dye with the two GMR wavelengths.Strong coupling local field is formed within the dye layer,which produces significantly low group velocity in these regions,lengthens the interaction time between light and matter,and enhance the excitation of the laser dye.Secondly,enhanced dye lasing emission by guided-mode resonance grating with mesoporous silica as spacing layer.mesoporous silica with low refractive index is introduced between the grating layer and the substrate layer of the GMR structure to significantly enhance the contact between local electric field and gain medium.The structure is a laser dye layer,a guided-mode resonance grating layer,a mesoporous silica layer,and a base layer from top to bottom.The laser dye is selected as IR-140 and dissolved in a polyurethane solvent.The guided-mode resonance grating layer is Titanium dioxide,and the base layer is glass.The optimal structure is obtained though optimizing the structural parameters such as thickness of each layer and grating period.Finally,a transmissive dye laser is proposed based on guided-mode resonance in coupled gratings,consisting of two identical grating membranes and laser dye doping polyurethane placed in the middle of the two grating membranes.Each grating membrane is composed of a surface-relief grating and a homogeneous layer on the substrate.When the pump energy is higher than the threshold,the laser can be emitted along the glass substrate's transmission direction.