Frequency and polarization emission properties of a photon-pair source based on a photonic crystal fiber

In this work, we experimentally demonstrate a photon-pair source with correlations in the frequency and polarization degrees of freedom. We base our source on the spontaneous four-wave mixing (SFWM) process in a photonic crystal fiber. We show theoretically that the two-photon state is the coherent superposition of up to six distinct SFWM processes, each corresponding to a distinct combination of polarizations for the four waves involved and giving rise to an energy-conserving pair of peaks. Our experimental measurements, both in terms of single and coincidence counts, confirm the presence of these pairs of peaks, while we also present related numerical simulations with excellent experiment-theory agreement. We explicitly show how the pump frequency and polarization may be used to effectively control the signal-idler photon-pair properties, defining which of the six processes can participate in the overall two-photon state and at which optical frequencies. We analyze the signal-idler correlations in frequency and polarization, and in terms of fiber characterization, we input the SFWM-peak experimental data into a genetic algorithm which successfully predicts the values of the parameters that characterize the fiber cross section, as well as predict the particular SFWM process associated with a given pair of peaks. We believe our work will help advance the exploitation of photon-pair correlations in the frequency and polarization degrees of freedom.

Optical Frequency Combs Generated in Silica Microspheres in the Telecommunication C-, U-, and E-Bands

Optical frequency combs (OFCs) generated in microresonators with whispering gallery modes are demanded for different applications including telecommunications. Extending operating spectral ranges is an important problem for wavelength-division multiplexing systems based on microresonators. We demonstrate experimentally three spectrally separated OFCs in the C-, U-, and E-bands in silica microspheres which, in principle, can be used for telecommunication applications. For qualitative explanation of the OFC generation in the sidebands, we calculated gain coefficients and gain bandwidths for degenerate four-wave mixing (FWM) processes. We also attained a regime when the pump frequency was in the normal dispersion range and only two OFCs were generated. The first OFC was near the pump frequency and the second Raman-assisted OFC with a soliton-like spectrum was in the U-band. Numerical simulation based on the Lugiato–Lefever equation was performed to support this result and demonstrate that the Raman-assisted OFC may be a soliton.

New bang-bang phase detectors for high-speed serial links

Bang-bang phase detector studies were carried out in this thesis. Based on the comparison of linear and non-linear phase detectors, a hybrid phase detector was proposed. It possesses the characteristics of two-XOR phase detectors and improved bang-bang phase detectors. PLLs with the proposed hybrid phase detector possess low timing jitter in lock states and a fast locking process. The effectiveness of the proposed hybrid phase detector was quantified by comparing the performance of three PLLs with identical loop components but different phase detectors. A new bang-bang phase detector with regenerative DFFs was also proposed. The regenerative bang-bang phase detector ensures a fast acquisition of incoming clocks. The effectiveness of the regenerative phase detector was assessed in a 2GHz PLL. A 1X bang-bang phase detector was proposed also. Compared to a 2X bang-bang phase detector, PLLs with a 1X bang-bang phase detector offer faster locking. A DFF frequency detector and a charge-pump frequency detector were also proposed. Both effectively detect the frequency difference.

New bang-bang phase detectors for high-speed serial links

Bang-bang phase detector studies were carried out in this thesis. Based on the comparison of linear and non-linear phase detectors, a hybrid phase detector was proposed. It possesses the characteristics of two-XOR phase detectors and improved bang-bang phase detectors. PLLs with the proposed hybrid phase detector possess low timing jitter in lock states and a fast locking process. The effectiveness of the proposed hybrid phase detector was quantified by comparing the performance of three PLLs with identical loop components but different phase detectors. A new bang-bang phase detector with regenerative DFFs was also proposed. The regenerative bang-bang phase detector ensures a fast acquisition of incoming clocks. The effectiveness of the regenerative phase detector was assessed in a 2GHz PLL. A 1X bang-bang phase detector was proposed also. Compared to a 2X bang-bang phase detector, PLLs with a 1X bang-bang phase detector offer faster locking. A DFF frequency detector and a charge-pump frequency detector were also proposed. Both effectively detect the frequency difference.

Resonator-free sub-MHz spectral dip in a twisted gain medium

Ultra-narrow spectral features are desirable for a broad range of applications, from precision spectroscopy to atomic clocks to slow-light and microwave photonics, and are conventionally realized using either ultrahigh-Q resonant structures or atomic resonances. Ultrahigh-Q structure often involves microfabrication, and suffers from loss mechanisms and manufacturing variations that cannot be easily compensated, whereas atomic resonances suffer from signal attenuation and tunability is a challenge. Here, we propose an entirely new way to achieve a sub-MHz and tunable spectral feature in a resonator-free gain medium, exploiting polarization pulling in a medium with frequency dependent polarization eigenmodes. To demonstrate a specific realization, we use Brillouin gain in a commercial spun fiber and experimentally achieve a 0.72 MHz spectral dip, which is to our knowledge, the narrowest spectral Brillouin feature ever reported. Furthermore, the simulation shows that the dip linewidth can be reduced to <0.1MHz, equivalent to a Q of almost 2 billion, by optimizing the birefringence and spun rate of the fiber. We also show that the linewidth, depth, and spectral location of this dip are all tunable on demand by controlling the pump frequency, pump power, and the input polarization of the signal. Its simplicity in implementation and broad applicability, its ultra-narrow linewidth, its tunability makes this approach extremely attractive for applications such as high precision metrology and microwave photonics.

Resonator-free tunable sub-MHz spectral dip in the Brillouin gain using spun birefringent fibers

Ultra-narrow spectral features are desirable for a broad range of applications, and they are conventionally realized using ultrahigh Q resonant structures. These structures typically require precision fabrication processes, and moreover, since they are passive, they suffer from signal loss. Here, we demonstrate a novel way to achieve sub-MHz tunable spectral dip in the Brillouin gain spectrum of a spun birefringent fiber (SBF) without loss, and without using a resonator. We show that this dip is unique to SBF, where its polarization eigenmodes are elliptical and frequency-dependent, and the dip only occurs when these orthogonal polarization eigenmodes of the SBF (at the respective pump and signal frequencies) are launched in counter-propagating directions. We experimentally demonstrate a 0.72 MHz spectral dip in the Brillouin gain spectrum of a commercial SBF which is to our knowledge, the narrowest SBS spectral feature ever reported. Furthermore, the linewidth, depth, and spectral location of this dip are tunable on demand by controlling the pump frequency, pump power, and the input polarization of the signal. Its simplicity in implementation, its ultra-narrow linewidth, and its tunability can have a wide range of potential applications, from slow-light to microwave photonics.

Dispersive-wave induced noise limits in miniature soliton microwave sources

Compact, low-noise microwave sources are required throughout a wide range of application areas including frequency metrology, wireless-communications and airborne radar systems. And the photonic generation of microwaves using soliton microcombs offers a path towards integrated, low noise microwave signal sources. In these devices, a so called quiet-point of operation has been shown to reduce microwave frequency noise. Such operation decouples pump frequency noise from the soliton’s motion by balancing the Raman self-frequency shift with dispersive-wave recoil. Here, we explore the limit of this noise suppression approach and reveal a fundamental noise mechanism associated with fluctuations of the dispersive wave frequency. At the same time, pump noise reduction by as much as 36 dB is demonstrated. This fundamental noise mechanism is expected to impact microwave noise (and pulse timing jitter) whenever solitons radiate into dispersive waves belonging to different spatial mode families.

Generation of Second Harmonics of Relativistically Self-Focused q-Gaussian Laser Beams in Underdense Plasma with Axial Density Ramp

An investigation on frequency doubling of intense laser beams through the phenomenon of second harmonic generation (SHG) in underdense plasmas has been presented. In order to increase the efficiency of S.H.G the density profile of plasma has been considered in the shape of upward ramp. When laser beam with frequency !0 propagates through plasma, it makes the plasma electrons to oscillate at pump frequency. These oscillations of plasma electrons in the presence of thermal velocity generate a plasma wave at frequency !0. The generated plasma wave beats with the pump beam to double its frequency. Variational theory has been adopted to find semi analytical solution of the wave equation for the slowly varying envelope of the laser beam. By using hydrodynamic fluid model of plasma, nonlinear current density for SHG has been obtained. Emphasis are put on investigation of the effect of various laser and plasma parameters on propagation dynamics of pump beam and the power of generated second harmonics.

Production Optimization for Natural Flow and ESP Well A Case Study on Well NS-5 Mishrif Formation-Nasriya Oil Field

As the reservoir conditions are in continuous changing during its life, well production rateand its performance will change and it needs to re-model according to the current situationsand to keep the production rate as high as possible.Well productivity is affected by changing in reservoir pressure, water cut, tubing size andwellhead pressure. For electrical submersible pump (ESP), it will also affected by numberof stages and operating frequency.In general, the production rate increases when reservoir pressure increases and/or water cutdecreases. Also the flow rate increase when tubing size increases and/or wellhead pressuredecreases. For ESP well, production rate increases when number of stages is increasedand/or pump frequency is increased.In this study, a nodal analysis software was used to design one well with natural flow andother with ESP. Reservoir, fluid and well information are taken from actual data of Mishrifformation-Nasriya oil field/ NS-5 well. Well design steps and data required in the modelwill be displayed and the optimization sensitivity keys will be applied on the model todetermine the effect of each individual parameter or when it combined with another one.