Characterization of focusing grating couplers for telecom wavelengths in the first and second diffraction order

In this work we studied how focusing grating couplers, developed for telecommunication C-band wavelength range, can be applied in the near infrared range. In the paper we presented prospects of usage of both first and second diffraction maxima of theoretically computed diffraction grating couplers for photonic aims. The dependence of the central wavelength of the grating on the etching depth of the photonic layer, on the period and filling factor of the grating was studied. We have compared our experimental results with numerical study, performed using finite elements method of solving differential equations. The work is important for different photonic applications and introduces new prospects in application of the already fabricated devices, developed for telecommunication wavelengths.

Focusing grating couplers for radio-frequency surface ion traps

We present a photonic integrated circuit design with multiple focusing grating couplers that can be used in a surface ion trap. This system allows transferring laser radiation from different laser sources to the ion trapped 240 μm above the surface for further manipulations.

Inverse design of grating couplers using the policy gradient method from reinforcement learning

We present a proof-of-concept technique for the inverse design of electromagnetic devices motivated by the policy gradient method in reinforcement learning, named PHORCED (PHotonic Optimization using REINFORCE Criteria for Enhanced Design). This technique uses a probabilistic generative neural network interfaced with an electromagnetic solver to assist in the design of photonic devices, such as grating couplers. We show that PHORCED obtains better performing grating coupler designs than local gradient-based inverse design via the adjoint method, while potentially providing faster convergence over competing state-of-the-art generative methods. As a further example of the benefits of this method, we implement transfer learning with PHORCED, demonstrating that a neural network trained to optimize 8° grating couplers can then be re-trained on grating couplers with alternate scattering angles while requiring >10× fewer simulations than control cases.

Silicon nitride ring resonator biosensors operated at 1310 nm wavelengths via TM-mode grating couplers

In this work, we demonstrate a full photonic integrated device for performing highly-sensitive biosensing using silicon nitride ring resonators propagating transverse-magnetic modes at wavelengths around 1310 nm. The device includes fully-etched grating couplers as interfaces with external optical fibres. Sensing experiments are performed in a microfluidic environment using bovine serum albumin and anti-bovine serum albumin as biological agents. In comparison with other photonic platforms based on ring resonators propagating transverse-electric modes, our device shows a better detection performance though the efficiency of the grating couplers can be further improved.

Optical Transmission Properties of Si3N4 Add-Drop Micro-Ring Resonator Induced by a Fabry–Perot Resonance Effect

To resolve the problem of miscellaneous peaks and improve the accuracy of data processing in micro-ring resonators (MRRs), we propose an optical transmission model based on a Fabry–Perot (F-P) resonance effect in a Si3N4 add-drop MRR-waveguide structure, which is analyzed using a coupled mode theory and stationary interference method. The analysis indicates the experimentally obtained miscellaneous peaks are mainly induced by the multiple reflections between the two end grating couplers, which form a F-P cavity. In addition, an anti-reflection film on the interface of the grating couplers is proposed to reduce the F-P resonance effect. This work could be useful to analyze optical transmission properties of other MRR-based structures.