Niall P. Kelly

Atomically Flat Low-Resistive Germanide Contacts Formed by Laser Thermal Anneal

In this paper, state-of-the-art laser thermal annealing is used to form germanide contacts on n-doped Ge and is systematically compared with results generated by conventional rapid thermal annealing. Surface topography, interface quality, crystal structure, and material stoichiometry are explored for both annealing techniques. For electrical characterization, specific contact resistivity and thermal stability are extracted. It is shown that laser thermal annealing can produce a uniform contact with a remarkably smooth substrate interface with specific contact resistivity two to three orders of magnitude lower than the equivalent rapid thermal annealing case. It is shown that a specific contact resistivity of 2.84 × 10-7 Ω·cm2 is achieved for optimized laser thermal anneal energy density conditions.

Coupled Cavity Single-Mode Laser Based on Regrowth-Free Integrated MMI Reflectors

A photonic integrated circuit is demonstrated that couples three Fabry-Pérot (FP) lasers together via an integrated star coupler. The FP lasers rely on a common cleaved facet and individual multimode interference reflectors (MIRs) for lasing operation. The MIRs are monolithically integrated with each FP laser using a single growth step, which allows for epitaxial regrowth-free processing. By suitable independent tuning of each Fabry-Pérot, a single mode operation and a mode selection can be attained from the coupled cavity system. The mode selectivity and side-mode suppression ratios of ~40 dB are demonstrated.

Monolithic Integration of Single Facet Slotted Laser, SOA, and MMI Coupler

We demonstrate a monolithically photonic integrated circuit (PIC) comprising a single facet slotted laser (SFSL), a semiconductor optical amplifier (SOA), and a 1 × 2 multimode interference (MMI) coupler. The integrated SFSL generates a tunable single longitudinal mode output, and utilizes a simplified fabrication process for the PIC when compared with distributed feedback or distributed Bragg reflector lasers by eliminating the epitaxial regrowth as well as the ebeam or holographically generated gratings. The integration technique is implemented by biasing the MMIs to transparency, which makes the fabrication comparable the standard ridge waveguide laser. The demonstrated PIC can be used as a 1 × 2 splitter or by integrating with other waveguide devices, such as laser, modulators, or SOAs, to realize different functionality.

Regrowth-free integration of injection locked slotted laser with an electroabsorption modulator

Optical injection locking was used to red shift an integrated semiconductor laser up to 30 nm away from the main free running lasing mode. This injection locking of the laser beyond its band edge enabled its integration with an electroabsorption modulator to produce a 2.5 Gb/s eye diagram. The electroabsorption modulator was shown to have a 3 dB bandwidth of 5.5 GHz, which was limited by the contact capacitance. This paper demonstrates that such devices could be applied in a regrowth free, monolithic coherent wavelength division multiplexing transmitter.

Regrowth-Free Single Mode Laser Based on Dual Port Multimode Interference Reflector

This letter demonstrates an InP-based photonic integrated circuit that utilizes an etched facet and a dual port multimode interference reflector to create a lasing cavity. The laser was fabricated using UV lithography and did not require any epitaxial regrowth. A single deep etched slot produced single mode behavior due to the coupled cavity effect. By varying the bias of the two sub cavities, mode selectivity with a side mode suppression ratio of 30 dB is demonstrated.

Single facet semiconductor laser with deep etched V-notch reflectors integrated with an active multimode interference reflector

Abstract A single mode laser based on novel deep etched V-notch reflectors is presented in this paper. The reported device has a stable single mode operation and a side mode suppression ratio of 37 dB. The laser is widely tunable and it can be fine-tuned. Moreover, the laser cavity is monolithically integrated with an active multimode interference reflector, and has a total length of .

On-Chip Investigation of Phase Noise in Monolithically Integrated Gain-Switched Lasers

Phase noise in gain-switched lasers is investigated theoretically using the semiconductor laser rate equations and compared with the experimental results from monolithically integrated devices. The phase noise of a gain-switched laser is modelled both with and without injection-locking using the rate equations for a single-mode laser. Phase noise is found to increase with gain-switching, and decrease when injection-locked to a master laser. This trend is then observed experimentally on-chip with monolithically integrated devices without the use of an isolator.

Monolithic CoWDM transmitter via integration of injection locked slotted laser with electroabsorption modulator

Photonic integrated circuits (PICs) based on InP have provided an effective solution to realize advanced functions at a system level with compact size. Such PICs have been demonstrated using various techniques such as epitaxial regrowth, hybrid/heterogeneous integration of InP and Silicon, and band gap engineering methods such as quantum well intermixing and selective area regrowth. However, a disadvantage of these methods when compared with regrowth free monolithic integration is their fabrication complexity and duration.

Widely tunable facetless regrowth-free semiconductor laser

A design for a laser is presented here, based on gold-coated on-chip etched facets and multimode interference (MMI) couplers [1]. The laser (shown in Fig. 1) was fabricated from commercially obtained regrowth-free 1550nm laser material and using exclusively standard UV lithography. The fabrication process is a two etch-depth process compatible with most standardised shared foundry processes [2]. The single-mode operation was achieved by the crossing of a central waveguide with the loop. The index perturbation caused by the crossing results in a reflection, making the device a multi-cavity laser and enabling single mode operation. Gold-coated etched facets are used as an on-chip reflective solution to remove the need for any cleaved facet from the design.

Integratable optical comb source for coherent communications systems

A coherent optical comb source is monolithically integrated. Optical combs were generated at 4 GHz and 5 GHz, with the combs produced independent of cleaved facets.