Volume 4, Issue 2 - Integrated Photonic Devices: Sensors, Materials, Systems / Guest Editors: Peter O’Brien, Meint K. Smit and Christian Koos

We demonstrate a wavelength domain-multiplexed (WDM) optical link relying on a single section semiconductor mode-locked laser (SS-MLL) with quantum dash (Q-Dash) gain material to generate 25 optical carriers spaced by 60.8 GHz, as well as silicon photonics (SiP) resonant ring modulators (RRMs) to modulate individual optical channels. The link requires optical reamplification provided by an erbium-doped fiber amplifier (EDFA) in the system experiments reported here. Open eye diagrams with signal quality factors (Q-factors) above 7 are measured with a commercial receiver (Rx). For higher compactness and cost effectiveness, reamplification of the modulated channels with a semiconductor optical amplifier (SOA) operated in the linear regime is highly desirable. System and device characterization indicate compatibility with the latter. While we expect channel counts to be primarily limited by the saturation output power level of the SOA, we estimate a single SOA to support more than eight channels. Prior to describing the system experiments, component design and detailed characterization results are reported including design and characterization of RRMs, ring-based resonant optical add-drop multiplexers (RR-OADMs) and thermal tuners, S-parameters resulting from the interoperation of RRMs and RR-OADMs, and characterization of Q-Dash SS-MLLs reamplified with a commercial SOA. Particular emphasis is placed on peaking effects in the transfer functions of RRMs and RR-OADMs resulting from transient effects in the optical domain, as well as on the characterization of SS-MLLs in regard to relative intensity noise (RIN), stability of the modes of operation, and excess noise after reamplification.

This review discusses photonic IC design software tools, examines existing design flows for photonics design and how these fit different design styles and describes the activities in collaboration and standardization within the silicon photonics group from Si2 and by members of the PDAFlow Foundation to improve design flows. Moreover, it will address the lowering of access barriers to the technology by providing qualified process design kits (PDKs) and improved integration of photonic integrated circuit simulations, physical simulations, mask layout, and verification.

Open access to generic technology platforms for photonic integrated circuit manufacturing enables low-cost development of application-specific photonic chips for novel or improved products. It brings photonic ICs within reach for many industrial users and research institutes, by moving toward a fabless business model. In the current status, InP-based open access manufacturing services are offered through multi-project wafer runs by Fraunhofer Heinrich Hertz Institut, SMART Photonics, and Oclaro. In this paper, we review state-of-the-art InP photonic integration technology platforms, present examples of complex InP photonic ICs developed in the generic technologies, and give a prospect for further development of these photonic integration platforms.

We developed a generic photonic integration platform based on selective area growth (SAG) by metal organic vapor-phase epitaxy (MOVPE) of AlGaInAs/InP multiple quantum well (MQW) material. For efficient and predictive band gap engineering of photonic integrated circuits, different SAG zones of active and passive function heterostructures are precisely modeled and characterized. With the vapor-phase diffusion model, using numerical simulations of finite volumes, we extracted the three effective diffusion lengths of Al, Ga, and In species. In our growth conditions, these lengths were 32, 65, and 14 μm, respectively. The Kardar-Parisi-Zhang (KPZ) equation, a classic approach to describe the growing interface profile, is used. AlGaInAs MQW properties are then simulated in terms of thickness, composition, band gap, and biaxial strain variations. Highly resolved μ-photoluminescence and optical interferometer microscopy measurements confirm the validity of the band gap and thickness variations for both bulk and MQW layers. A new diffractometer, with a submillimeter X-ray spot, was used to study the structural properties of the MQW in the center of the SAG area. As an application, we present the realization and operation of full-monolithic high-speed advanced modulation format transmitters based on novel prefixed optical phase switching by fast electro-absorption modulators.

A review is given of a number of lasers in a form of photonic integrated circuits realized on InP substrate using a generic integration approach. The potential of these photonic circuits lies in their compactness, low power consumption, and significant reduction of fabrication cost by realization in generic foundry runs. Generic integration platforms offer the possibility of realizing functionally advanced photonic circuits using combinations of just a few standardized and parameterized building blocks. This vibrant field opens new doors to innovative product development for SMEs as well as curiosity-driven research.

Photonic applications based on planar waveguide technology impose stringent requirements on properties such as optical propagation losses, light coupling to optical fibers, integration density, as well as on reliability and reproducibility. The latter is correlated to a high level of control of the refractive index and waveguide geometry. In this paper, we review a versatile dielectric waveguide platform, called TriPleX, which is based on alternating silicon nitride and silicon dioxide films. Fabrication with CMOS-compatible equipment based on low-pressure chemical vapor deposition enables the realization of stable material compositions being a prerequisite to the control of waveguide properties and modal shape. The transparency window of both materials allows for the realization of low-loss waveguides over a wide wavelength range (400 nm–2.35 μm). Propagation losses as low as 5×10 -4 dB/cm are reported. Three basic geometries (box shell, double stripe, and filled box) can be distinguished. A specific tapering technology is developed for on-chip, low-loss (<0.1 dB) spotsize convertors, allowing for combining efficient fiber to chip coupling with high-contrast waveguides required for increased functional complexity as well as for hybrid integration with other photonic platforms such as InP and SOI. The functionality of the TriPleX platform is captured by verified basic building blocks. The corresponding library and associated design kit is available for multi-project wafer (MPW) runs. Several applications of this platform technology in communications, biomedicine, sensing, as well as a few special fields of photonics are treated in more detail.

Most deposition chambers sold into the optical coating market today are outfitted with an automated control system. We surveyed several of the larger equipment providers, and nine of them responded with information about their hardware architecture, data logging, level of automation, error handling, user interface, and interfacing options. In this paper, we present a summary of the results of the survey and describe commonalities and differences together with some considerations of tradeoffs, such as between capability for high customization and simplicity of operation.