Circular-core single-mode polymer waveguide for high-density and high-speed optical interconnects application at 1550 nm

Abstract

We demonstrate circular-core 1550 nm single-mode polymer waveguides with a graded-index profile fabricated by commercially available UV-curable epoxies using so-called mosquito method. The relative index difference ∆n of the waveguides was designed to be 0.46% in order to guarantee both single-mode operation and good compatibility with standard single-mode fiber. Accurate refractive index tuning of monomer for core construction was realized by mixing the core and cladding epoxies properly. The core pitch of the waveguides was chosen to be 50 μm to satisfy the requirements for high-density on-board optical interconnects. Both the optical characteristics and high-speed performances of the waveguides were comprehensively studied at 1550 nm. The measured transmission and coupling loss are 0.79 dB/cm and 0.78 dB, respectively. The waveguides exhibit an inter-channel crosstalk as low as -45 dB, and a 3 dB misalignment tolerance larger than ± 4 μm on the input and output facet in both horizontal and vertical directions. NRZ signal at a data rate of 25 Gb/s was transmitted over a 10 cm-long waveguide. There is no obvious degradation on the eye diagram due to the insertion of the waveguide and error free transmission was successfully obtained. Our results imply that the fabricated single-mode polymer waveguides have good potential in high-density and high-speed optical interconnects application.

Design and Fabrication of Broadband Polymer Mode (De)Multiplexer Using a Direct Inscribing Method

“…The fabrication process are shown in Fig. 4(a) [26]. Firstly, the cladding monomer is coated on a glass substrate.…”

“…The fabricated mode multiplexer shows the lowest IL of 2.7 dB at 1550 nm and the highest IL of 4.7 dB at 1600 nm. The total length of the fabricated mode (de)multiplexer is about 30.0 mm and the propagation loss of the single-mode waveguide is about 0.8 dB/cm at 1550 nm [26].…”

“…Compared with the lithography method, the Mosquito method is photomask-free and can inscribe three dimensional (3D) polymer waveguides with circular cores using a simple procedure [24], [25]. Compared with the femtosecond laser direct writing technique, the Mosquito method has advantages such as low cost, high fabrication speed, tunable refractive index profile and large applicable size [26], [27]. Using the Mosquito method, tapered waveguides can be fabricated easily by programming the needle-scan velocity.…”

“…On the other hand, the process of inscribing neighboring cores may cause unwanted turbulence on the core shape and core position of the waveguide owing to the liquid state of the monomers. We have fabricated single-mode polymer waveguides and 3D directional coupler cover C-band by using the Mosquito method [26], [27]. The mode (de)multiplexer with a coupling ratio (CR) of less than 83% from 1500 to 1560 nm has also been fabricated [28].…”

Low loss, flexible single-mode polymer photonics

“…Despite these advantages, single-mode polymer waveguides generally exhibit much higher propagation losses compared to their multi-mode counterparts. While propagation losses as low as 0.03 dB/cm have been demonstrated in multi-mode waveguides [25][26][27][28][29][30][31][32][33], the minimal loss figures in single-mode waveguides remain at 0.14 dB/cm (at 808 nm wavelength [33]) mainly due to increased modal overlap with roughness and defects at the core/cladding interfaces.…”