Chris L. M. Daunt

Single mode lasers based on slots suitable for photonic integration

The single mode laser structure based on etched slots suitable for photonic integration is presented in this paper. The laser is made completely dependent on a group of slots on one side of the laser cavity. The fabricated 750 μm long single section laser exhibits a threshold current and a slope efficiency of about 32 mA and 0.11 mW/mA, respectively. The stable single mode operation has been observed with a side mode suppression ratio (SMSR) of around 47 dB at a current injection of 100 mA for the fabricated laser. To solve the yield problem associated with the cleaving of the laser structure, the two-section single mode laser based on slots was further present. By tuning the back section current, stable single mode performance with a SMSR of more than 42 dB is observed over a wide temperature from 15°C to 65°C for the fabricated 750 μm long two-section laser. The presented laser structure just needs a single wafer growth and can be fabricated by standard photolithography and has very strong potential for use in optical communication systems.

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.

NiGe Contacts and Junction Architectures for P and As Doped Germanium Devices

In this paper, the contact resistivity of NiGe on n-doped Ge is extracted. Although phosphorus is the slowest n-type dopant in terms of diffusion in Ge, the corresponding contact resistivity data for this dopant are sparse. Contact resistivity dependence on implant dose will be determined, as well as a comparison of phosphorus- and arsenic-doped Ge layers. The impact of high contact resistance is evaluated for future technology n-type metal-oxide-semiconductor germanium devices.

Integration of AlInGaAs-MQW Fabry–Pérot Lasers With Emission at Two Wavelength Ranges via Quantum-Well Intermixing

We demonstrate ridge waveguide lasers based on AlInGaAs multiple quantum wells emitting at 1434 and 1541 nm on the same laser bar using quantum-well intermixing with dielectric capping layers. The internal quantum efficiencies are measured to be 61% and 72% and the internal losses are 49 and 23 cm-1 for lasers with intermixing promoted and inhibited, respectively. The characteristic temperatures are found to be approximately 50 K for lasers emitting around 1433 nm and 75 K for those emitting around 1541 nm.

Zero-Bias High-Speed Edge-Coupled Unitraveling-Carrier InGaAs Photodiode

The traveling-wave edge-coupled unitraveling-carrier (UTC) photodiode was designed and fabricated for zero-bias high-speed communication system application. A 40-μm-long 5-μm-wide UTC waveguide device demonstrated 13-GHz 3-dB bandwidth and up to 10-mA photocurrent without saturation in our measurement range under zero bias.

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.

Compact Electroabsorption Modulators for Photonic Integrated Circuits, Using an Isolated Pedestal Contact Scheme

We demonstrate a shallow ridge waveguide, lumped element electroabsorption modulator (EAM) based on AlInGaAs multiple quantum wells, operating with input powers up to 8 dBm. The device was isolated between two DC controlled sections, using angled etched slots in the waveguide, minimizing optical feedback, while also providing 40-KΩ resistance between devices. The EAM uses a planar isolated pedestal contact with a benzocyclobutene bridge, allowing for a small contact footprint of just 0.024 mm2, while being suitable for flip-chip packaging. The parasitic capacitance was measured to be 19.6 fF, and the EAM has a f3dB bandwidth of 42 GHz.

Directly Modulated Laser Diode Module Exceeding 10 Gb/s Transmission

A directly modulated laser diode module with over 10 Gb/s transmission and its performance, packaging process, and manufacturability are presented. The butterfly package consists of a V-connector, heat sink, and L-shaped microstrip line (MSL) which includes an integrated impedance matching resistor. The optical system consists of a 1.3- distributed feedback laser and a micro lens with isolator. A large modulation bandwidth of up to 15 GHz was obtained, and the eye diagram for 10 Gb/s modulation was clearly visible. Importantly, using an L-shaped MSL with integrated impedance matching resistor design, the module design is significantly simplified and can provide flexibility to insert various optical coupling systems. Moreover, since the laser was mounted directly on Kovar heat sink, optical output power reduction by thermal effects was 1 dB up to 50°C without active cooling. As a result of the simplified module configuration with flexibility, the module packaging process may be highly efficient for mass production.

Quantum well intermixing in AlInGaAs MQW structures through impurity-free vacancy method

We report on quantum well intermixing of AlInGaAs-MQWs using the impurity-free vacancy diffusion method with dielectric capping layers which has potential for realization of photonic integrated circuits. The extent of the bandgap shifts with respect to different dielectric capping layers and alloy temperatures are investigated. The intermixing inhibitor and promoter are then integrated using combination of SiO2 and SiNx dielectric capping layers which shows a differential photoluminescence wavelength more than 110 nm. Based on this developed intermixing technique, we have fabricated AlInGaAs-InP based material stripe lasers emitting at two different wavelength ranges centered at 1519 nm and 1393 nm respectively. Characterizations including the current-voltage and electroluminescence measurements show that the integration of two-bandgaps can be achieved and furthermore a differential wavelength in lasing spectra up to 120 nm is demonstrated.

Single facet slotted Fabry-Perot laser and its application in photonic integrated circuits

In this paper, a single facet slotted Fabry-Perot (FP) laser is demonstrated to provide tunable, single mode operation and has been monolithically integrated into a photonic integrated circuit (PIC) with semiconductor optical amplifiers and a multimode interference coupler. These lasers are designed by incorporating slots into the ridge of traditional FP cavity lasers to achieve single mode output, integrability and tunability. With the feature size of the slots around 1μm, standard photolithographic techniques can be used in the fabrication of the devices. This provides a time and cost advantage in comparison to ebeam or holographic lithography as used for defining gratings in distributed feedback (DFB) or distrusted Bragg reflector (DBR) lasers, which are typically used in PICs. The competitive integrable single mode laser also enables the PIC to be fabricated using only one epitaxial growth and one etch process as is done with standard FP lasers. This process simplicity can reduce the cost and increase the yield.