Abstract
By taking advantages of the two-photon polymerization induced by femtosecond laser and the versatility of the femtosecond laser microfabrication, we demonstrate a femtosecond laser microfabricated polymeric grating for spectral tuning, in which gratings of different thicknesses achieve gradual tuning of a white incident light into output lights of different colors ranging from cyan to red, which is in good agreement with the simulation. Through the selection of different grating parameters, the technique developed in this study offers the possibility to tailor the performance of the grating to achieve specific grating efficiency or complete extinction at specific wavelengths, which is promising for measurements and applications in spectroscopy, sensing, integrated optical systems, and biomedicine.
Highlights
IntroductionBroadly to say, any operation to achieve the selection, filtering, or control of wavelengths in order to obtain specific spectral components of light, is essential in measurements with extensive uses in spectroscopy, microscopy, sensing, photochemistry, lasers, and optical communication
Spectral tuning, broadly to say, any operation to achieve the selection, filtering, or control of wavelengths in order to obtain specific spectral components of light, is essential in measurements with extensive uses in spectroscopy, microscopy, sensing, photochemistry, lasers, and optical communication
Wavelength tuning in the visible spectral range, commonly known as color filtering, is important for applications, such as a color filter consisting of an array of annular apertures in a gold film for transmission measurement [12], a multilayered structure incorporating a subwavelength metal-dielectric grating for better reflection resonance and color effects [13], excitation of surface plasmonic effects in nanostructured materials [14,15,16], and plasmonic color filters adopting freestanding resonant membrane waveguides [17]
Summary
Broadly to say, any operation to achieve the selection, filtering, or control of wavelengths in order to obtain specific spectral components of light, is essential in measurements with extensive uses in spectroscopy, microscopy, sensing, photochemistry, lasers, and optical communication. Wavelength tuning in the visible spectral range, commonly known as color filtering, is important for applications, such as a color filter consisting of an array of annular apertures in a gold film for transmission measurement [12], a multilayered structure incorporating a subwavelength metal-dielectric grating for better reflection resonance and color effects [13], excitation of surface plasmonic effects in nanostructured materials [14,15,16], and plasmonic color filters adopting freestanding resonant membrane waveguides [17] Most of these reported components are either relatively large in volume for use in free-space optics, costly in the fabrication techniques, or are mostly incompatible with integrated systems, especially for the case of biomedical applications, for example, a lab-on-a-chip platform, where footprint and the compatibility with the fluidic environment are crucial [18]. Despite the use of relatively slow line-by-line approach, the femtosecond laser microfabrication technique adopted in this study exhibits its salient advantages of flexibility and versatility, in which it is easy to write gratings with different specifications (periodicity Λ, thickness d, and width a) by adjusting the laser parameters (i.e., laser power, scan speed, and focusing condition), and offers the significant merits in the adjustability of the grating performance for measurements
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