2021/07/01 by Ibrahim Ghannam, Ghannam, Ibrahim, Bin Shen +5
Engineering · Physics and Astronomy · #Advanced Fiber Laser Technologies #Applied Physics (physics.app-ph) #FOS: Physical sciences #Optics (physics.optics) #Photonic and Optical Devices #Semiconductor Lasers and Optical Devices
paper · pdf · doi:10.48550/arxiv.2107.00586
openalex publication_date 2021/07/01 · openalex created_date 2022/07/25 · openalex updated_date 2026/07/28
We demonstrate an external cavity laser formed by combining a silicon nitride\nphotonic integrated circuit with a reflective semiconductor optical amplifier.\nThe laser uses an alignment tolerant edge coupler formed by a multi-mode\nwaveguide splitter right at the edge of the silicon nitride chip that relaxes\nthe required alignment to the III-V gain chip and equally splits the power\namong its two output waveguides. Both the ground and first order mode are\nexcited in the coupler and reach the quadrature condition at the waveguide\njunction, ensuring equal power to be coupled to both. Two high-quality-factor\nring resonators arranged in Vernier configuration close a Sagnac loop between\nthe two waveguides. In addition to wideband frequency tuning, they result in a\nlonger effective cavity length. The alignment tolerant coupler increases the\nalignment tolerance in the two directions parallel to the chip surface by a\nfactor 3 relative to conventional edge couplers, making it ideal for gain chip\nintegration via pick-and-place technology. Lasing is maintained in a\nmisalignment range of \±6 \μm in the direction along the edge of the\nchip. A Lorentzian laser linewidth of 42 kHz is achieved.\n