In this thesis, We have fabricated 1.55

In this paper, a distributed Electroabsorption Modulator (EAM) monolithically integrated with Semiconductor Optical Amplifier (SOA) is analyzed. Using the distributed effects on the optical modulation and amplification, several advantages have been found in this work, such as high-speed modulation, microwave performance, low nose properties, and low chirp, which is quite fitted to the requirements of optical fiber communications. EAMs have been widely used due to high-speed, high extinction ratio, the compactness, and the capability of integration. However, due to the highly loaded capacitance in the waveguide, EAMs generally suffer from high microwave reflection and thus low modulation efficiency during high-speed modulation. By the distributed structure, SOA-integrated EAMs can not only enhance the impedance match by adopting distributed high impedance transmission line (HITL), but also offer optical gain. By the optical processing scheme of re-amplification and re-modulation, it also has been found that the extra amplified spontaneous emission (ASE) noise coming from SOA can be reduced to get lower noise figure (NF). Appling the saturation on SOA, the positive frequency chirp of EAM can be compensated to give overall low chirp. By the distributed structure, chirp compensation has been realized by this characterization. In this work, the distributed EAM-SOA scheme and the traditional single section EAM-SOA scheme are used for comparison, higher speed and lower NF are observed in distributed scheme. Due to impedance matching improvement in distributed scheme, a -3dB bandwidth of higher than 40GHz and 40Gbit/s data transmission is achieved, while a 15GHz of -3dB bandwidth is obtained in single device. Also, in 10Gbit/s data transmission, a 3dB lower of power penalty occurs in distributed scheme, while the lower NF is the mainly dominating mechanism.

In this thesis, we use InP based multiple quantum well epi-wafer with modulation doping in the active layer to design the semiconductor optical amplifier and ring laser for the optical communication at 1.55£gm wavelength. We also finish the mask design and fabrication of theses two devices. Besides, we have established an optical measurement system, including the L-I measurement, the optical spectrum measurement and the far field measurement, to test the device parameters. In the device process, we use the new method, called the Multi-Step Undercutting, to precisely control the undercut in the wet etching process. With this technique, we can get a smooth and vertical sidewall for our devices. For the semiconductor optical amplifier, we design two different types, one is the Fabry-Perot Amplifier and the other is the Traveling Wave Amplifier. We use the Multi-Step Undercutting process in the fabrication of these two devices. The main parameters for semiconductor optical amplifier are the change of the output power versus the input current, the spontaneous emission spectrum and the photocurrent spectrum. For the ring laser, we combine the concept of Loop Mirror and Asymmetric Mach-Zehnder Interferometer to obtain the laser with good side mode suppression for a single wavelength light source.

In this thesis, we focus on the investigation of semiconductor optical amplifier and ring laser. We use InP based multiple quantum well epi-wafer with modulation doping in the active layer to design the semiconductor optical amplifier and ring laser for the optical communication at 1.55£gm wavelength. We combine the concept of Loop Mirror and Asymmetric Mach-Zehnder Interferometer to obtain the laser with good side mode suppression for a single wavelength light source. For the semiconductor optical amplifier, we design two different types, one is the Fabry-Perot Amplifier and the other is the Traveling Wave Amplifier. Furthermore, We use the Multi-Step Undercutting process in the fabrication of these two devices. We have established an optical measurement system, including the L-I measurement, the optical spectrum measurement and the far field measurement, to test the device parameters. After annealing, these devices with two different serial number exhibited the contact resistances of 9£[ and 16£[, respectively. Under CW operation, these FPA exhibited the threshold current of 62mA and 70mA at 20¢J, respectively. The stimulated emission wavelength was at 1531nm and 1522nm, respectively.

The work of this thesis includes the growth of TE polarization and polarization insensitive semiconductor optical amplifier structures by molecular beam epitaxy. The former is suited to fabricate the SOA and laser of the emitter, the latter is suited to fabricate the SOA of the repeater and receiver. The materials of InAl(1)As, InGa(1)Al(2)As and InGa(2)As were used to be the cladding layer, SCH layer and quantum well(QW), respectively. The first kind of our SOA structures is for 1.55-£gm TE polarization. The materials of InGa(1)As and InGa(2)As were used to be QW and sub-well, respectively. The second kind of our SOA structures is for 1.55-£gm polarization insensitive. To get polarization insensitive characteristics we use tensile strained InGa(3)As material and add two very thin compressive strain layers, InGa(1)As, in QWs to be sub-wells to mostly confine hh1 state. It has the effect of reducing red shift on the e1-hh1 transition and help to partially balance the strain in QW before the thickness of the tensile strained InGa(3)As exceeds one half of the critical layer thickness. These two kinds of structures include three QWs with modulation doping. It can reduce transparency current and noise figure and increase the saturation output power of SOA with the n-type modulation doping. We had successfully grown the polarization insensitive SOA structure for 1.52-£gm. The wavelength of TE polarization SOA structures we grew were at 1.45(µm) and 1.47(µm) and there were somewhat differences between the designed and grown. We can increase the PL efficiency after rapid thermal annealing at 550¢J for 30(s)~45(s).

This thesis is shown the implementation of the linearization techniques such as feedforward and pre-distortion feedback linearization to suppress the optical components nonlinearities caused by the fibre and semiconductor optical amplifier (SOA). The simulation verified these two linearization techniques for single tone direct modulation, two tone indirect modulation and ultra wideband input to the optical fibre. These techniques uses the amplified spontaneously emission (ASE) noise reduction in two loops of SOA by a feed-forward and predistortion linearizer and is shown more than 6dB improvement. Also it investigates linearization for the SOA amplifier to cancel out the third order harmonics or inter-modulation distortion (IMD) or four waves mixing. In this project, more than 20 dB reductions is seen in the spectral re-growth caused by the SOA. Amplifier non-linearity becomes more severe with two strong input channels leading to inter-channel distortion which can completely mask a third adjacent channel. The simulations detailed above were performed utilizing optimum settings for the variable gain, phase and delay components in the error correction loop of the feed forward and Predistortion systems and hence represent the ideal situation of a perfect feed-forward and Predistortion system. Therefore it should be consider that complexity of circuit will increase due to amplitude, phase and delay mismatches in practical design. Also it has describe the compatibility of Software Defined Radio with Hybrid Fibre Radio with simulation model of wired optical networks to be used for future research investigation, based on the star and ring topologies for different modulation schemes, and providing the performance for these configurations.

Semiconductor optical amplifiers (SOA) and electroabsorption modulators (EAM) have been become vital elements to obtain high-output-power and high-speed optical signal in the optical fiber communications. In this paper, we propose a novel type cascaded integrated SOAs and EAMs, which are monolithically integrated in the same chip without any regrowth. In the active region, high electron bandgap offset material, InGaAsP/InAlGaAs, is used in order to get high optical gain and also high modulation. Using cascaded SOAs and EAMs, high impedance of microwave stripe lines are the bridges connecting the small EAM elements, bring up higher impedance and thus enhancing the microwave transmission. The optical waveguide is made by selectively undercut etching InGaAsP/InAlGaAs material in order to reduce the optical scattering loss and also the microwave loss due to the low parasitic capacitance. The processing is described by the following steps: (1) ion implantation to get electrical isolation; (2) wet etching to form the optical waveguide ridge; (3) e-gun evaporation to get n- and p- metalization ; (4) spinning PMGI as planarization; (5)Final thick metalizations as for microwave transmission line. The final integrated cascaded SOAs and EAMs has been successfully fabricated and measured. In comparison with single EAM, higher than 10GHz of ¡V3dB electrical transmission has been found, indicating the cascaded integration structure has better impedance matching and also higher electrical transmission. The measured optical gain is higher than 5dB with 11dB/V modulation efficiency at excitation wavelength of 1568nm.

Traveling-wave semiconductor optical amplifiers¡]TWSOAs¡^of symmetric and asymmetric multiple quantum wells¡]MQWs¡^have been implemented by using angled-facet structures. The asymmetric MQWs structures are designed to increase the wavelength range of the gain spectrum. The angled-facet structures, which can suppress gain ripple from FP resonance, are of 3mm-wide and 700mm-long ridge waveguides, and of different angles¡]q¡^at 3o, 5o, 7o, and 9o. From Marcuse¡¦s model, the calculation shows that the angled-facet structures have reflectivities lower than 10-4. We have also developed a single-trench process to fabricate the angled-facet TWSOAs. The l=1.55mm asymmetric structure, which shows a low epitaxial quality of large leakage current, is not suitable for SOA application. For the l=1.3mm asymmetric structure, the threshold current¡]Ith¡^at q=0o was 22.5mA, while at q=7o the Ith increased to 45mA. We have also measured the spectrum below threshold current. The differences between FP resonance peak and valley become smaller at larger q. We estimated that the reflectivity is about 0.2 at 5o. The results show that the reflectivity was decreased by angled-facet structure.

Silicon photonics provides an environmentally sustainable pathway to a more robust data infrastructure. To compensate for optical power losses, methods of amplification are required; specifically, amplifiers that can fit in a small footprint for applications in data centres. Semiconductor optical amplifiers (SOA) provide such a solution, and can be fabricated using III-V ternary or quaternary materials to enhance optical signals through a device on the scale of most CMOS components. This research sought to fabricate an InGaAsP multiple quantum well semiconductor optical amplifier using the facilities in McMaster University’s Centre for Emerging Device Technologies (CEDT). A ridge waveguide laser diode was first fabricated and validated, then altered by applying an anti-reflective coating to the waveguide facets to suppress reflections in the Fabry-Perot cavity in an attempt to create an SOA. The design process and fabrication methodology are explained, including an analysis of failed methodologies. Characterization measurement techniques are then detailed for the fabricated devices. Finally, the performance of the devices is presented, and future steps are suggested for improving the fabrication process to enhance device characteristics. The fabricated laser diodes produced an output power in excess of 20 mW at a peak wavelength near 1580 nm. The subsequently coated devices proved difficult to measure, displaying a maximum of 0 dB or 1 dB gain when checked for amplification, with suspicions that output loss (and therefore gain) was higher than measured. The coated devices exhibited gain saturation between -10 and 0 dBm of input power. Owing to the shapes of their characteristic curves, it was determined that SOA devices were successfully created. / Thesis / Master of Applied Science (MASc)

With the rapid and ongoing developments in telecommunication and electronic warfare technology, faster and more flexible systems are in demand. Wideband signal processing is thus needed to implement such systems. Microwave photonics has been introduced as a tool for achieving such ultra broadband signal processing. Instantaneous Frequency Measurement (IFM) receivers play an important role in electronic warfare. They have been developed as a means of obtaining a rapid indication of the presence of a threat and to roughly identify the frequency of the threat signals. They also have the advantages of low-cost, compactness and moderate to good sorting capability in an interference-free environment. The main limitation of the traditional RF IFM receivers is constrained bandwidth. Microwave Photonic IFMs have been considered, but the main disadvantages of photonic realization of the recent IFM receiver is cost. This work aims to propose and demonstrate low-cost photonic IFM receivers with a broad frequency measurement range. The proposed methods are based on the use of photonic mixing to down-convert the RF modulated optical signals to DC. In a RADAR warning receiver, usually a bank of IFMs is required. Increasing the numbers of IFMs requires an increase in the number of photo-detectors. Thus if low-frequency, low-cost detectors can be used, then the net system cost will be reduced significantly. The concept is proven and the issues arising are analyzed. In the proof of concept system, measurement of the RF frequency required advance knowledge of the RF power. Secondly, the use of co-axial RF cables as delay elements limited the bandwidth and increased bulk. Using a photonic hybrid approach to achieve orthogonal measurements was demonstrated as a means of dentifying both RF frequency and power simultaneously and independently. Employing all optical mixing removed the need for co-axial RF cables delays using non-linear optical devices such as Semiconductor Optical Amplifier (SOA) and Highly Non-Linear Fiber (HLNF). The last investigation is to improve the sensitivity of the implemented IFM system. The sensitivity of the implemented system is characterized first and a lock-in technique is employed to improve the sensitivity of the system. The final system achieves a sensitivity of -41 dBm which is comparable with the traditional RF IFM receivers.