Demonstration of an On-Chip TE-Mode Optical Circulator

Abstract

In this paper, an on-chip optical circulator on the InP-membrane-on-Si (IMOS) platform is demonstrated. The circulator is composed of two multi-mode interferometers (MMIs), four polarization converters (PCs), and a Cerium-doped Yttrium Iron Garnet (Ce:YIG) die. The Ce:YIG die is adhesively bonded on the InP membrane via a 125-nm thin bonding layer. Nonreciprocal phase shift (NRPS) is employed in the presence of a transverse magnetic field. The device works as a 4-port optical circulator with a maximum optical isolation of 27.0 dB and a minimum optical isolation of 18.6 dB for the TE mode. The measured optical isolation bandwidth is 0.12 nm. Two methods are proposed in order to improve the optical isolation bandwidth.

Efficient heat sink by ultrathin BCB bonding for InP membrane lasers

“…Reducing the thickness of the BCB layer as spun on the wafer has limitations. Examples of bonding of a die 25) with 25 nm thick BCB or a 4 × 4 mm garnet 26) with 125 nm thick BCB were demonstrated previously. However, in practice, it is highly challenging to achieve a defect-free bonding of a non-planar 3 inch wafer when using BCB thickness equal to or less than the maximum step height in the wafer topography.…”

On-Chip Broadband, Compact TM Mode Mach–Zehnder Optical Isolator Based on InP-on-Insulator Platforms

“…We designed two waveguide structures on the InP-on-insulator platform, corresponding to the feasible processes of direct bonding [ 39 , 40 ] and BCB adhesive bonding [ 36 , 41 ], respectively, as shown in Figure 2 a,b. For the direct-bonded waveguide structure, a single crystalline layer of Ce:YIG was grown on a (111)-oriented substituted gadolinium gallium garnet (SGGG) substrate.…”

“…Then, a layer of adhesion promoter AP3000 was applied and gently baked at 135 °C for 5 min to enhance the adhesion of BCB. Finally, under vacuum and continuous pressure, the Ce: YIG mold was placed into contact with the upper surface of the BCB [ 36 ]. Both waveguide structures exhibited asymmetric refractive index distributions in the y-direction and the underlying SiO 2 cladding was thick enough to block out the influence of the substrate.…”

“…Heterogeneous integration of InP-based active-layer lasers with SiO 2 /Si substrates has reached the commercial stage [ 33 , 34 , 35 ]. Reniers et al developed an on-chip magneto-optical circulator on the InP-on-insulator platform with good performance [ 36 ]. However, there remains an absence of development and simulation of integrated optical isolators.…”