Demonstration of Large Mode-Hop-Free Tuning in Narrow-Linewidth Heterogeneous Integrated Laser

Abstract

Continuously tunable lasers with a narrow linewidth are at the core of a large number coherent optical systems. Integration of these devices on a single chip will enable a large number of applications that require minimal size, weight, power, and cost. In this work, we demonstrate a 3 nm-continuously tunable laser operating around 1550 nm with a narrow intrinsic linewidth of 5.7 kHz. The device is fully integrated on a siliconon-insulator platform and the optical gain is provided by a bonded III-V layer. The narrow laser linewidth is attained with an extended cavity that consists of a Vernier ring-based mirror and a passive waveguide. To reach the record continuous (mode-hopfree) tuning range of 3 nm (375 GHz), we demonstrate a method for synchronously tuning the Vernier resonances together with the cavity longitudinal modes, both thermally controlled. In the current laser, the mode-hop-free tuning range is limited by the maximum heating power, but it can be extended over more than 10 nm (1.25 THz) by optimizing the integrated heater design.

Simulation Analysis of Mode Hopping Impacts on OFDR Sensing Performance

“…To delve deeper into the impact of mode hopping on distributed strain sensing, an optical frequency jump was also introduced into the sweep, as depicted in Figure 5, with T h set to a random value between 0 and T. In this simulation, all other parameters remained consistent with those employed in the mode-hopping-free strain sensing simulation. The electric field of the reference arm's signal mirrored that of the distance sensing simulation with mode hopping, as specified by Equation (18).…”

“…Such abrupt shifts in wavelength or optical frequency are generally deemed unsuitable for distributed fiber sensing or LiDAR applications. As a result, most research and development efforts to advance high-performance tunable diode lasers have been directed toward mitigating mode hopping issues and ensuring stable, single-frequency operation [16][17][18].…”