The interaction of light with nanostructures having variation in the refractive index on the order wavelength or subwavelength generates so many rich physical concepts that cannot be easily observed in the conventional medium. As inverse design methods provide effective optimization of the refractive index distribution that is not possible by conventional methods based on the intuition of researcher, they have been recently used in the design of nanophotonic devices. In this study, 2D integrated photonic devices which split optical power equally and exhibit the negative refraction and photonic nanojet were designed through the objective-first inverse design algorithm. Firstly, the optical power splitters (1×N) separate the optical power of the TE or TM fundamental mode at 1.55 μm wavelength up to the four output waveguides. The output powers are approximately equal (± 3%) and their modes are the same input signal modes. Secondly, the negative refractive index medium is designed in the wavelength range of 1.5-1.6 μm, and incident angle of 45°- 60°. Finally, a beam with full width at half maximum (FWHM)<λ/3 and depth of field>2λ is performed in the scope of the photonic nanojet. Also, the designed structures are discretized by acceptable performance losses considering the production conditions. As a result, 4-channel optical power splitter, negative refractive index medium, and photonic nanojet are revealed using the objective-first algorithm for the first time to the best of our knowledge.
We design two different compact and low-loss 2D T-junction optical mode demultiplexing by using objective-first inverse design algorithm. These devices are designed for transverse-electric (TE) and transverse magnetic (TM), separately. High device performances were achieved for the specific designs of 1×2, 1×3 mode demultiplexers with fractional footprints at the orders of a few microns. The presented T-junction 1×2, 1×3 devices operate at the C-band; the device has a footprint of 2.8 μm × 2.8 μm and 4.44 μm × 4.44 μm, respectively and splits TE/TM<sub>0,1,2</sub> modes efficiently. The modal efficiencies at the corresponding target wavelength of each vertically or horizontally aligned channels were obtained mostly to be nearunity together with minimal crosstalk ranges of around <-30 dB. The electromagnetic inverse design allowing the implementation of more than three output channels along with the novel functionalities will pave the way for compact and manufacturable 1xN couplers, which is of ultimate significance for integrated photonics.
We demonstrate efficient and compact 1xN wavelength-demultiplexing by using objective-first inverse design algorithm. Ultra-high device performances were achieved for the certain designs of 1x2, 1x3, and 1x4 demultiplexers with very small footprints at the orders of a few microns. The presented 1x2, 1x3, and 1x4 devices operate at the wavelength sets of 1.31μm, 1.55 μm; 1.31 μm, 1.47 μm, 1.55 μm, and; 1.31 μm, 1.39 μm, 1.47 μm, 1.55 μm, respectively. The transmission efficiencies at the corresponding target wavelengths of each vertically or horizontally aligned channels were obtained mostly to be near-unity together with very small crosstalk ranges of around 0.01% - 1.2%. The inverse design approach allowing the implementation of more than four output channels together with the novel functionalities will pave the way for compact and manufacturable 1xN couplers, which is of ultimate significance for integrated photonics.
We propose and demonstrate compact on-chip optical filters with ultra-high efficiencies, which are designed via the recently-emerged objective-first inverse design algorithm. The all-dielectric high-pass, low-pass and all-pass filters presented in this study operate within the telecommunication wavelength spectrum of 1260 - 1625 nm. The high-pass filter shows an outstanding performance for the transmission efficiency higher than the frequency of 210 THz and an effective suppression of the other spectral region. Also, the proposed low-pass filter exhibits high transmission and significant blocking at the ranges of 170 Thz-205 Thz and 205 Thz-240 Thz, respectively. Furthermore, the designed allpass filter possesses notable spectral transmissivity and blocking characteristics. The promising features of the structures were also verified via the finite-difference time-domain method. Such manufacturable optical filters with great device performances are favorable candidates for next-generation photonic applications.