We propose a technique for additive manufacturing of polymer step-index (STIN) optics. The process is composed of aerosol jet multi-material deposition followed by laser-assisted stereolithography in an alternating fashion to fabricate multi-material three-dimensional objects. The layer-wise dynamic tuning of the refractive index provides the possibility to fabricate optics with tailored index profiles. The index range achieved by the presented approach is considerably higher than the common index tuning techniques. Using this technique, a planar multilayer STIN lens is fabricated. The index profile of the fabricated lens has similar progression to the designed profile. In addition, through simulation and also optical characterization, the lensing functionality of the structure is observed.
An integrated refractive index gas sensor working in the Mid infrared (MIR) region and utilizing suspended silicon waveguide is presented. Although many integrated refractive index gas sensors have been proposed in the literatures, their operating wavelength is limited to the near infrared range. Our proposed gas sensors can operate in the mid infrared up to 10μm, were many gases have their absorption fingerprints in order to enhance the sensing performance. A finite difference solver is used to perform the sensitivity analysis of the suspended silicon waveguide in the MIR range for gaseous medium. The analysis shows that a suspended silicon waveguide can achieve high waveguide sensitivity with a minimal mode loss. Thus, we designed a high performance Mach Zehnder Interferometer (MZI) gas sensor using a suspended silicon waveguide as the sensing arm. Three dimensional finite difference time domain (3D-FDTD) solver is used in the design and optimization of two designs. One for the wavelength interrogation scheme of detection and another one for the intensity interrogation scheme. The first design, exhibits high wavelength sensitivity S=7028 nm/RIU and can reach high figure of merit (FOM) of around 180 RIU-1 for both wavelength and intensity interrogation methods with only 250μm sensing arm length. The second design furtherly enhances the intensity interrogation FOM to reach 370RIU-1 at the same length. Intensity interrogation needs only a laser source and a detector. Hence, using our sensor in intensity interrogation based read-out offers compact, low cost and mass scale fabrication which makes our proposed sensor a good platform for lab on chip technology.
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