Hybrid-Integrated Tunable Hollow Waveguide DBR Laser
We propose a novel hybrid-integrated tunable laser with a hollow waveguide distributed Bragg reflector, enabling a wide continuous tuning with a single-tuning parameter. The wavelength tuning of hollow waveguide lasers is demonstrated for the first time.
A hollow waveguide Bragg reflector: A tunable platform for integrated photonics
Abstract Hollow waveguides are promising candidates for applications in sensing and high-power transmission. Flexible design and cost effective fabrication of hollow waveguides make it possible to realize integrated devices with small temperature dependence, tight control on optical confinement and tailorable characteristics. One of the potential applications of hollow waveguide is a tunable Bragg reflector, which can be used as building block for integrated photonics. In this review, integrated tunable Bragg reflector based on hollow-core optical waveguide is reviewed and presented; this Bragg reflector offers variable characteristics and design flexibility for applications in reconfigurable integrated photonic devices and circuits. Variety of tunable optical functions can be realized with on-chip Bragg reflector based on hollow waveguide, few of them are discussed in this review. Ultra-wide tuning in Bragg wavelength and on-chip polarization control can be realized using 3D hollow waveguide. A tapered 3D hollow waveguide Bragg reflector for an adjustable compensation of polarization mode dispersion (PMD) is then discussed. The utilization of a high-index contrast grating in hollow waveguide is demonstrated to reduce the polarization dependence and reflection-bandwidth. The polarization- and bandwidth control may be useful for realizing polarization insensitive devices and semiconductor lasers with ultra-wide tuning.
Tunable planar polymer Bragg gratings having exceptionally low polarization sensitivity
We report fabrication of planar polymer Bragg gratings that can be thermally tuned 20 nm with very low polarization sensitivity, (/spl lambda//sub TE/-/spl lambda//sub TM/)</spl plusmn/0.05 nm, throughout the tuning range. Polarization sensitivity in a planar film is caused by an anisotropic effective refractive index in the film typically resulting from strain. Strain in polymer Bragg gratings is caused by the photopolymerization and the thermal annealing processes utilized for the grating fabrication. For the case of polymer Bragg gratings, we show for the first time that fabrication-induced strain can be nearly eliminated by laser etching parallel trenches into the polymer layers on each side of the grating. The improvement in polarization sensitivity depends strongly on the trench separation, the thermal annealing process, and the grating tuning method.