Jeroen Bolk

An introduction to InP-based generic integration technology

Photonic integrated circuits (PICs) are considered as the way to make photonic systems or subsystems cheap and ubiquitous. PICs still are several orders of magnitude more expensive than their microelectronic counterparts, which has restricted their application to a few niche markets. Recently, a novel approach in photonic integration is emerging which will reduce the R&D and prototyping costs and the throughput time of PICs by more than an order of magnitude. It will bring the application of PICs that integrate complex and advanced photonic functionality on a single chip within reach for a large number of small and larger companies and initiate a breakthrough in the application of Photonic ICs. The paper explains the concept of generic photonic integration technology using the technology developed by the COBRA research institute of TU Eindhoven as an example, and it describes the current status and prospects of generic InP-based integration technology.

Fast random bits generation based on a single chaotic semiconductor ring laser

Here, we numerically and experimentally demonstrate that, by combining two post-processing methods (multi-bit extraction and bitwise OR-exclusive (XOR) operations). in a single chaotic semiconductor ring laser (SRL), it is possible to generate true random bits with a bit rate up to 40 Gb/s from a chaos bandwidth of ≈ 2 GHz, thanks to the device ability of lasing in two directional modes and the fact that the two mode signals have low correlations. In addition, SRLs can be easily implemented on chip.

Heterogeneously integrated III-V/silicon distributed feedback lasers

Heterogeneously integrated III-V-on-silicon second-order distributed feedback lasers utilizing an ultra-thin DVS-BCB die-to-wafer bonding process are reported. A novel DFB laser design exploiting high confinement in the active waveguide is demonstrated. A 14 mW single-facet output power coupled to a silicon waveguide, 50 dB side-mode suppression ratio and continuous wave operation up to 60°C around 1550 nm is obtained.

Semiconductor Ring Laser With On-Chip Filtered Optical Feedback for Discrete Wavelength Tuning

We introduce a novel concept of discretely tunable semiconductor lasers with on-chip filtered optical feedback. The integrated device is based on a semiconductor ring laser that can sustain two counter-propagating modes. By means of a directional coupler, part of the light emitted by the laser is coupled out to a feedback section integrated on the same chip. The feedback section contains two arrayed waveguide gratings and a set of semiconductor optical amplifiers to provide filtering of particular longitudinal modes sustained by the ring cavity. By controlling the current injected into the semiconductor optical amplifiers, single mode operation in both directions is achieved. In this paper, the design, characterization, and modeling of the device is presented.

Directional control of optical power in integrated InP/InGaAsP extended cavity mode-locked ring lasers

We report on a passively mode-locked InP/InGaAsP multiple quantum well semiconductor ring laser that operates at a 20 GHz repetition rate and around 1575 nm wavelength. The device has been realized using the active-passive integration technology in a standardized photonic integration platform. We demonstrate experimentally for the first time to our knowledge that the relative positioning of the amplifier and absorber in a monolithically integrated ring laser can be used to control the balance of power between counterpropagating fields in the mode-locked state. The directional power balance is verified to be in agreement with a model previously reported.

Wavelength Switching Speed in Semiconductor Ring Lasers With On-Chip Filtered Optical Feedback

We experimentally and numerically characterize the wavelength switching speed of a tunable semiconductor ring laser using filtered optical feedback. The feedback is realized employing two arrayed-waveguide gratings to split/recombine light into different wavelength channels. The wavelength tuning and switching is controlled by changing the currents injected in semiconductor optical amplifiers in the feedback section. A wavelength switching speed of a few nanoseconds is achieved. We investigate also the effect of the feedback parameters and noise strength on the wavelength switching speed.

Controlled multiwavelength emission using semiconductor ring lasers with on-chip filtered optical feedback

We report on an integrated approach to obtain multiwavelength emission from semiconductor ring lasers with filtered optical feedback. The filtered feedback is realized on-chip employing two arrayed-waveguide gratings to split/recombine light into different wavelength channels. Through experimental observations and numerical simulations, we find that the effective gain of the different modes is the key parameter which has to be balanced in order to achieve multiwavelength emission. This can be achieved by tuning the injection current in each amplifier.

Digitally tunable dual wavelength emission from semiconductor ring lasers with filtered optical feedback

We report on a novel integrated approach to obtain dual wavelength emission from a semiconductor laser based on on-chip filtered optical feedback. Using this approach, we show experiments and numerical simulations of dual wavelength emission of a semiconductor ring laser. The filtered optical feedback is realized on-chip by employing two arrayed waveguide gratings to split/recombine light into different wavelength channels. Semiconductor optical amplifiers are placed in the feedback loop in order to control the feedback strength of each wavelength channel independently. By tuning the current injected into each of the amplifiers, we can effectively cancel the gain difference between the wavelength channels due to fabrication and material dichroism, thus resulting in stable dual wavelength emission. We also explore the accuracy needed in the operational parameters to maintain this dual wavelength emission.

Monolithic Nanosecond-Reconfigurable 4

A monolithic InGaAsP/InP 4 × 4 cross-connect is designed, fabricated and demonstrated. Each of the four inputs fan out to two stages of semiconductor optical amplifier-based gates to perform broadband-input-selection and wavelength-specific-selection. Stages of parallel cyclic arrayed waveguide grating routers and wavelength-agnostic fan-ins allow independent electronically controlled routing of four unique wavelength channels between the four inputs and outputs. The circuit is realized within a 15 mm area on a multi-project wafer. Circuit performance is evaluated by resolving optical power loss within the circuit to show component level performance at and close to design specification. Data routing experiments for wavelength multiplexed signals are performed and quantified in terms of optical power penalty. Multi-path routing is performed with both co- and counter-propagating data. Bi-directional and fast reconfigurable routing is similarly quantified. Low power penalty of less than 1 dB is measured for the simultaneous routing of data over multiple circuit paths.

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All-optical regeneration has attracted growing interest due to the possibility to increase the all-optical reach. However, to be really competitive with optoelectronic regenerators, all-optical regenerators should process an entire wavelength division multiplexed (WDM) signal comb at once and significantly reduce the footprint and the power consumption, as possible, in principle, by exploiting photonic-integrated circuits (PICs). Moreover, since constant envelope modulation format signals have come into play in recent years, all-optical regenerators dealing with a multiplex of these signals are of particular interest. This paper presents a monolithically integrated indium-phosphide-based PIC acting as an all-optical regenerator for constant envelope WDM signals. The regeneration scheme is based on hard-limiting amplification in saturated semiconductor optical amplifiers (SOAs), which removes the signal intensity noise. The presented PIC, designed and fabricated within the JePPIX technology platform, can handle up to four WDM signals, which are demultiplexed and enter an array of SOAs to undergo regeneration before being multiplexed again. The channel-by-channel regeneration of both polarization shift keying and frequency shift keying signals at 10 Gb/s is experimentally demonstrated in terms of Q-factor improvement.