A micromachined tunable coupled-cavity laser for wide tuning range and high spectral purity

Tunable coupled-cavity semiconductor laser based on a half-wave bow-tie coupler

We propose and experimentally demonstrate a widely tunable coupled-cavity semiconductor laser based on a novel half-wave bow-tie coupler. The laser comprises two resonate cavities connected through the bow-tie coupler consisting of two back-to-back corner reflectors connected with a short waveguide, which produces a half-wave cross-coupling phase with an optimum coupling coefficient for achieving high mode selectivity. No complex grating or multiple epitaxial growth is needed. By tuning a single electrode at a fixed temperature, 29.6 nm wavelength tuning covering 38 channels with 100 GHz frequency spacing is achieved experimentally, with a side-mode suppression ratio of over 35 dB.

Widely tunable multimode-interference based coupled cavity laser with integrated interferometer

We present a simple to process tunable laser, fabricated in a low-cost generic fabrication process and based on two coupled Fabry-Perot cavities. The complex coupling coefficients of the coupling element are analytically derived from a 3×3 MMI using coupled mode theory and chosen to maximize the SMSR during lasing operation. Additionally, one of the cavities contains a reflective interferometer, which acts as coarse wavelength selector. This interferometer is derived from a Michelson Interferometer, by replacing the two independent mirrors with our optimized coupling element, leading to a doubled Free Spectral Range. As a result, we obtained a tuning range of 26 nm with potential for beyond 40 nm, a SMSR larger than 40 dB and fiber coupled power up to 9 dBm.

Spectrum control by anisotropy in a cylindrical microcavity

Spectrum control by anisotropy in a cylindrical microcavity made of electric anisotropic medium was studied. A finite-difference time domain method for electric anisotropic medium and Volume-average Effective Permittivity approximation are applied to calculate the resonant frequencies and quality factors of Whispering-gallery modes. The resonant frequency for different whispering-gallery modes has a similar shift in direct proportion to the relative difference of two principal refractive indices. The quality factors decay exponentially due to directional emission when the difference of two principal refractive indices increases. This novel tuning characteristic of anisotropic cylindrical microcavity will play an important role in many areas, such as light source with tunable wavelength, tunable filter and sensor.