The erbium-based optical amplifier (EDFA) plays a vital role in the global fibre-optic telecommunication network. However, there are two main issues with current EDFAs, their bulky size means that they cannot be integrated into silicon-based photonic devices, and they need high pump power to produce optical gain. Here, a potential organo-erbium gain system has been invented, which could be operated under a low pump power and integrated onto a silicon-based device. The fully-fluorinated organic erbium complex [Er(ftpip)3] was mixed with a fully-fluorinated organic zinc complex [Zn(F-BTZ)2], acting as a chromophore over the visible range. The composite provides extraordinary sensitisation from the Zn(F-BTZ)2 to Er(ftpip)3 over a broad-visible band, which is compatible with high power LEDs, whilst the erbium ions have a new record of IR emission lifetime of ~ 0.8 ms (quantum yield = ~ 7%). The integrated sensitisation is ~ 104 times that of the intrinsic excitation into erbium. This system has been integrated into an organic light emitting diodes (OLEDs) demonstrating that the energy transfer is dominated by triplet states of the Zn(F-BTZ)2. This is used for explaining the photoluminescence saturation and large pump-rate, with the composite being excited by a low power diode laser on the chromophore units. This composite-system was used to fabricate a slab waveguide, in which an relative gain of 3.4 dB/cm was achieved when excited by a diode laser with 3 mW. A microscopic-optic setup was designed to measure IR line strengths of erbium ions in crystals of complexes, which were included in theoretical calculation to obtain accurate quantum yield for IR emission of erbium ions. The inclusion of IR line strengths measured from crystals is found to be crucial for Judd-Ofelt parameterisation on organic erbium complexes. It was demonstrated that fluorination could increase the line strengths of hypersensitive transitions and IR transition for 1.5 μm band.

Abstract During the last decade, the maximum capacity of an optical fiber transmission line more than doubled every year to match the fast-growing communication need. The technology break through in dry fiber fabrication opens the possibility for fiber bandwidth all the way from 1.3

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.

No description available.

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)

Doctor of Philosophy / Department of Physics / Hongxing Jiang / III-nitride photonic devices such as photodetectors (PDs), light emitting diode (LEDs), solar cells and optical waveguide amplifiers were designed, fabricated and characterized. High quality AlN epilayers were grown on sapphire and n-SiC substrates by metal organic chemical vapor deposition and utilized as active DUV photonic materials for the demonstration of metal-semiconductor-metal (MSM) detectors, Schottky barrier detectors, and avalanche photodetectors (APDs). AlN DUV PDs exhibited peak responsivity at 200 nm with a very sharp cutoff wavelength at 207 nm and extremely low dark current (<10 fA), very high breakdown voltages, high responsivity, and more than four orders of DUV to UV/visible rejection ratio. AlN Schottky PDs grown on n-SiC substrates exhibited high zero bias responsivity and a thermal energy limited detectivity of about 1.0 x 1015 cm Hz1/2 W-1. The linear mode operation of AlN APDs with the shortest cutoff wavelength (210 nm) and a photocurrent multiplication of 1200 was demonstrated. A linear relationship between device size and breakdown field was observed for AlN APDs. Photovoltaic operation of InGaN solar cells in wavelengths longer than that of previous attainments was demonstrated by utilizing InxGa1−xN/GaN MQWs as the active layer. InxGa1-xN/GaN MQWs solar cells with x =0.3 exhibited open circuit voltage of about 2 V, a fill factor of about 60% and external quantum efficiency of 40% at 420 nm and 10% at 450 nm. The performance of InxGa1-xN/GaN MQWs solar cell was found to be highly correlated with the crystalline quality of the InxGa1-xN active layer. The possible causes of poorer PV characteristics for higher In content in InGaN active layer were explained. Photoluminescence excitation studies of GaN:Er and In0.06Ga0.94N:Er epilayers showed that Er emission intensity at 1.54 µm increases significantly as the excitation energy is tuned from below to above the energy bandgap of these epilayers. Current-injected 1.54 µm LEDs based on heterogeneous integration of Er-doped III-nitride epilayers with III-nitride UV LEDs were demonstrated. Optical waveguide amplifiers based on AlGaN/GaN:Er/AlGaN heterostructures was designed, fabricated, and characterized. The measured optical loss of the devices was ~3.5 cm−1 at 1.54 µm. A relative signal enhancement of about 8 dB/cm under the excitation of a broadband 365 nm nitride LED was achieved. The advantages and possible applications of 1.54 µm emitters and optical amplifiers based on Er doped III-nitrides in optical communications have been discussed.

Conjugated polymers are organic materials which are attractive as optoelectronic devices because they have a combination of broad band emission, high gain, versatility in processing, are ductile and can be electrically pumped. This thesis describes work conducted on such conjugated polymers as amplifier devices. The conjugated polymers used in this thesis were MEH-PPV, F8BT, GP1302 and ADS233YE. The amplifier devices used were grating coupled and end coupling waveguides. Amplification of light was demonstrated and characterised on single and multiple pulses using the grating coupled structure. Single pulse measurements obtained gains of 21 and 17 dB in a 1 mm long waveguide using the conjugated polymers MEHPPV and F8BT. Annihilation rate was also analysed in the single pulse method with MEH-PPV, giving a value of γ ≈ (3 ± 0.1) x 10⁻⁹ cm³/s. Amplification of a single pulse led to demonstrate amplification and the capability of the amplifier to function with multiple pulses, which resulted in F8BT being used as the gain medium. An average gain of 18 dB was obtained with F8BT in a 1 mm waveguide channel. Amplification was also investigated with end coupled waveguides. This led into investigating a suitable material or suitable combination of material for amplification with the waveguides. Switching of an amplified pulse was attempted on F8BT and GP1302 in the amplifier device at 5 kHz. Switching of F8BT was problematic which lead to attempt switching in GP1302 which was a co-polymer of PFO and F8BT. A 70 % switching effect was obtained with GP1302. Gain recovery dynamics of F8BT, GP1302 and ADS233YE was also investigated. These measurements established a switching rate of 500 GHz for GP1302 and ADS233YE, and F8BT showed partial gain recovery indicating the presence of long lived species. Switching was also attempted on a polymer laser. This resulted in a 100 % switched pulse with a combination of weak pump and strong switch pulse of 40 nJ and 2 μJ respectively. And a strong pump and weak switch pulse of 200 and 50 nJ respectively. Temporal delay of the switch pulse relative to the pump pulse resulted in re-timing of the laser output. Amplification and switching of light pulses were also attempted at a higher repetition rate of 50 kHz with F8BT, GP1302, ADS233YE and MEH-PPV. This resulted in strong amplification of light in MEH-PPV and F8BT with gains of 21 and 13 dB respectively in a waveguide length of 422 μm. Weak amplification of light in ADS233YE and GP1302 was also obtained with a maximum gain of 8 and 3 dB respectively. Switching was attempted on MEH-PPV and ADS233YE.

Recently, with the escalating demands for optical communications, the need for bandwidth in optical communication network has increased. The technology breakthrough in dry fiber fabrication opens the possibility for fiber bandwidth from 1.3 to 1.6 £gm. Cr4+:YAG double-clad crystal fiber (DCF) grown by the co-drawing laser-heated pedestal growth method has a strong spontaneous emission spectrum from 1.3 to 1.6 £gm. Such fiber is, therefore, eminently suitable for broadband optical amplifier, amplifier spontaneous emission (ASE) light source, tunable solid-state laser, and optical coherence tomography (OCT) applications. In this thesis, multilayer dielectric thin films were directly deposited by E-gun coating onto the end faces of the heterostructure Cr4+:YAG DCF. In this way we have successfully improved the extracted ASE power by the high reflection (HR) coatings. The backward ASE in the fiber reflected and propagates with gain through the fiber in the forward direction. In dual-pump scheme, as much as 1.7 mW power (DCF length is 9.5 cm) of collimated output ASE was achieved. The dual-pump scheme and HR thin films provided 1.6 time improvements of the ASE output power. For broadband optical amplifier in dual-pump and double-pass scheme, a 3.7-dB gross gain and a 0.7-dB net loss (DCF length is 8.7 cm) at 1.4-£gm signal wavelength have been successfully developed with HR coatings onto one of the Cr4+:YAG DCF end faces. In addition, we have successfully developed the Cr4+:YAG DCF fiber laser by direct HR coatings onto fiber end faces. A record-low threshold of 96 mW (DCF length is 1.6 cm) with a slope efficiency of 6.9% was achieved at room temperature. It is more than four times lower than any previously reported Cr4+:YAG lasers.

Today s supercomputers require interconnection networks with high bandwidth and low latency to exploit parallelism. The data vortex is an all optical path interconnection network defined and then proven to achieve high level of message acceptance and low levels of message latency. In this thesis research, three enhancements to the data vortex are defined and tested for performance. They are compared to an unmodified data vortex using the average latency and offered traffic acceptance rates as metrics. Minimal angle counts are established where express lane enhancements are established. An express lane enhancement allows exploitation of locality yielding an 8% to 12 % reduction in average latency and a 4% to 6% increase in message acceptance. Semi-Express lanes cannot effectively exploit locality but still yield a 20% increase in message acceptance and a 4% decrease in average latency. Express outputs can exploit locality for a 28% to 32% increase in message acceptance and 12% to 15% decrease in average latency.