Marko Galarza

Compact and highly-efficient polarization independent vertical resonant couplers for active-passive monolithic integration

Compact low-loss polarization independent vertical coupling between a 1.55 microm InGaAsP bulk active waveguide and a passive waveguide based on bimodal interference is presented. Simulation results show low coupling loss (<0.1 dB) over coupler lengths more than 5 times shorter than using the adiabatic design. The concept avoids submicron photolithographic features and shows acceptable fabrication tolerances.

A new spot-size converter concept using fiber-matched antiresonant reflecting optical waveguides

We report on a new concept for InGaAsP-InP 1.55-/spl mu/m lasers with integrated spot-size converters (SSCs) based on antiresonant reflecting optical waveguides (ARROW). The mode expanders consist of a laterally tapered active region on top of a fiber-matched passive slab waveguide. The large slab mode is laterally confined by an antiresonant configuration of a couple of lateral waveguides defined in the same fabrication process as the active ridge. This feature makes the presented spot-size transformer as simple to fabricate as a standard waveguide, only requiring a planar growth step and a single conventional etch process. The fabricated tapers exhibit a low transformation loss and reduce the coupling loss to standard single-mode fibers from 8 to 4 dB. We also analyze by simulation two variants of the concept proposed in this work, including a taper structure for a buried waveguide, which are expected to show better performance. Simulation results show fiber-coupling efficiencies as low as 2.4 and 1.1 dB for both variants.

Compact spot-size converters with fiber-matched antiresonant reflecting optical waveguides

We propose a concept for InGaAsP-InP 1.55-microm lasers integrated with spot-size converters based on modal interference between the modes of the structure formed by an active waveguide and an underlying fiber-matched antiresonant reflecting optical waveguide. Simulation results show that the spot-size converters exhibit low transformation loss, and narrowed far-field emission patterns (10 degrees x 20 degrees) and reduce the coupling loss to standard single-mode fibers from 8 to 2.6 dB over lengths approximately 200 microm shorter than the adiabatic concept. A tolerant design to fabrication variations is also proposed, which could be realized by standard processing techniques.

Mode-expanded 1.55-/spl mu/m InP-InGaAsP Fabry-Perot lasers using ARROW waveguides for efficient fiber coupling

We report on a new concept for InGaAsP-InP 1.55-/spl mu/m lasers with integrated spot-size converters based on antiresonant reflecting optical waveguides (ARROWs). The mode expanders consist of a tapered active region on top of a fiber-matched passive vertical ARROW waveguide. The large fundamental leaky mode with its low propagation loss makes ARROW waveguides useful for fiber coupling functions and avoids typical growth-related problems as encountered with traditional designs. The tapers exhibit a low transformation loss and narrowed far-field emission patterns (10.4/spl deg//spl times/22/spl deg/) and reduce the coupling loss to standard single-mode fibers from 8 to 2.6 dB. We also present the design and the results obtained with a relaxed ARROW design with thinner ARROW layers to reduce the overall layer stack thickness considerably, without affecting the fiber-coupling performance. The antiresonant effect has also been used for the lateral confinement of the fiber-matched mode. This feature makes the presented spot-size transformer as simple to fabricate as a standard waveguide, only requiring a planar growth step and a single conventional etch process. The fabricated tapers exhibit a low transformation loss and minimum far-field divergence angles of 13.8/spl deg//spl times/30.8/spl deg/, reducing the coupling loss to a standard single-mode fiber from 8 to 4 dB. We also analyze by simulation two variants of the concept proposed in this work, including a taper structure for a buried waveguide, which are expected to show better performance. Simulation results show fiber-coupling efficiencies as low as 2.4 and 1.1 dB and reduced far-field divergence angles as low as 7.2/spl deg//spl times/14/spl deg/ and 7.2/spl deg//spl times/9/spl deg/ for both variants.

Experimental assessment of access guide first-order mode effect on multimode interference couplers

Experimental results on multimode interference (MMI) coupler performance, when the access waveguides are not single mode, are shown. The 3-dB MMI couplers based on restricted interference are fabricated in InP/ InGaAsP buried waveguides. Unbalanced measurements for different excitation conditions are shown. A drastically unbalanced decline of 30% is reported for an alignment deviation of 6 ?m. Less critical effects are measured when misalignment is controlled below 2 ?m. A beam propagation method and modal analysis are used to validate experimental results.

Simple-to-fabricate and highly efficient spot-size converters using antiresonant reflecting optical waveguides

We report on a new concept for InGaAsP-InP 1.55 μm lasers with integrated spot-size converters based on antiresonant reflecting optical waveguides (ARROW). The mode expanders consist of a laterally tapered active region on top of a fiber-matched passive slab waveguide. The large slab mode is laterally confined by an antiresonant configuration of a couple of lateral waveguides defined in the same fabrication process as the active ridge. This feature makes the presented spot-size transformer as simple to fabricate as a standard waveguide, only requiring a planar growth step and a single conventional etch process. The fabricated tapers exhibit a low transformation loss and reduce the coupling loss to standard single-mode fibers from 8 to 4 dB. We also analyze by simulation two variants of the concept proposed in this work, including a taper structure for a buried waveguide, which are expected to show better performance. Simulation results show fiber-coupling efficiencies as low as 2.4 and 1.1 dB for both variants.