Ph.D Thesis


Ph.D StudentEyal Ori
SubjectHigh Speed Quantum Dot Lasers and Amplifiers - Static
Dynamic, Optical and Electrical Temperature
Stability
DepartmentDepartment of Electrical and Computer Engineering
Supervisor PROFESSOR EMERITUS Gad Eisenstein
Full Thesis textFull thesis text - English Version


Abstract

High speed semiconductor electro optic devices have a strong demand in the rapidly increasing optica  l communication and data com networks. Low-dimensional nanostructure lasers and amplifiers are expected to substitute their quantum well (Qwell) counterparts since they are superior, in principle, in every important aspect, first and foremost in efficiency speed and temperature insensitivity. Efforts have been devoted during the past years to achieve nanostructure lasers with a broad modulation bandwidth, a low frequency chirp, low sensitivity to temperature, and a near zero linewidth enhancement factor (also known as α-factor). Particularly, 1.55-µm InP-based quantum dash dot (QD) lasers hold a great promise for long-haul transmission and short-range links (in data centers) compared to 1.3-µm QD laser sources grown on GaAs substrate.

Incorporating tunneling injection structures to such InAs QD diode Lasers expands modulation bandwidth and bit rates limits, with evidence of lower carrier temperature near the active junction.

Using such devices as amplifiers can allow operation with lower temperature stabilization, decreasing system power consumption in terms of joule per bit. Incorporation with silicon photonics has also matured using bonding and recently epitaxial growth, however, more research is needed for the epitaxially grown structures.

In this dissertation, we address QD lasers and amplifiers. The first part investigates new designs that include a tunneling injection scheme and separately QD lasers with a top electrode device. In the second part, standard design lasers are coated and used for amplification, exposing the superior properties of QD gain material, especially temperature stability and multiwavelength amplification. For this investigation, electro optic properties and their temperature dependence in static and dynamic regimes are measured and extracted, parameters such as modulation bandwidth, differential gain, maximum bitrate, gain, saturation power, spectral shifts and their temperature dependence.

QD based electro optic sources hold the promise to provide several of the most important requirements for directly modulated lasers: high speed, low chirp, and most important - temperature insensitivity. This addresses mainly the speed and temperature sensitivity issues while examining integration on top of silicon for photonic integrated circuits.